As a result of the fast growing scale of IEEE 802.11 networks, problems such as low signal-to-noise ratio, collision, and small-scale fading have seriously impacted the performance of IEEE 802.11 networks. In this work, we describe a novel cross-layer analysis method, using the combination of received channel power sampling at the physical (PHY) layer and information at the medium access control (MAC) layer. The proposed method analyzes the causes of error frames by recording samples of received channel power at the physical layer on a small time scale (5  μs) and employs the particle filter-based joint likelihood ratio method in order to detect changes in the received channel power and to isolate models of the changes within the time domain. At the same time, it determines the source and the destination addresses of the error frames by decoding packet physical addresses at the MAC layer and then locates the error source. On the basis of the proposed method, optimizations are possible both at the MAC layer and the PHY layer. The simulation and the experimental validation were both carried out for the proposed method. The simulation validation was carried out in order to validate the accuracy of the particle filter-based joint likelihood ratio method for fault detection and for model isolation using the proposed method. We compared the performance of the extended Kalman filter and the particle filter-based likelihood ratio method using the non-Gaussian situation for the proposed method. We then performed several experiments in order to validate the accuracy of the proposed method for error source diagnosis. We also show the applications of the proposed method. The experiments under actual scene showed that different optimizations can be made to optimize the actual wireless local area network by determining the three different causes of the errors. Copyright © 2013 John Wiley & Sons, Ltd.

The method analyzes the causes of error frames by recording samples of received channel power at the physical layer on a small time scale (5 μs), and employs the Particle Filter-Based Joint Likelihood Ratio method in order to detect changes in the received channel power and to isolate models of the changes within the time domain. At the same time, it determines the source and the destination addresses of the error frames by decoding packet physical addresses at the MAC layer, and then locates the error source.

With the exception of required time synchronization, the Reservation-ALOHA (R-ALOHA) protocol is simple to implement and suitable for medium access control in ad hoc wireless networks. In this paper, we propose an innovative protocol, referred to as Reservation ALOHA with priority (PR-ALOHA) that provides differentiated services on the basis of traffic priority. To date, the carrier sense multiple access/collision avoidance (CSMA/CA) protocol has been widely used for this purpose by employing an interframe spacing (IFS) for priority service, that is, nodes ready for packet transmissions are required to wait for an IFS amount of time, where a shorter IFS is used to gain faster access to the radio channel. However, sensing and collision avoidance mechanisms make CSMA/CA unsuitable for delay-sensitive applications, that is, congested scenarios with high traffic. In contrast, the proposed PR-ALOHA protocol may be considered a good candidate for such applications. In this paper, the performance of the PR-ALOHA protocol is investigated analytically and by simulation. Its comparison with regular R-ALOHA is also carried out. Modeling and simulation results of PR-ALOHA show that PR-ALOHA improves the performance of high-priority traffic with limited effect on normal network traffic. Thus, PR-ALOHA may be useful in vehicular communications, where traffic may be separated into emergency messages having high priority and multimedia messages having low priority. Copyright © 2013 John Wiley & Sons, Ltd.

In this paper, we propose an innovative protocol, referred to as Reservation ALOHA with priority (PR-ALOHA) that provides differentiated services based on traffic priority. In the carrier sense multiple access/collision avoidance (CSMA/CA) protocol, nodes ready for packet transmissions are required to wait for an interframe spacing amount of time. This PR-ALOHA protocol may be considered a good candidate to solve the CSMA/CA issues, which may be employed in vehicular communications, where traffic may be separated into emergency messages having high priority and multimedia messages having low priority.

Several scheduling techniques were designed for the base station (BS) of IEEE 802.16e wireless interoperability of microwave access networks. However, depending on the BS scheduler alone to determine the servicing order of each connection might affect the accuracy of the scheduling process because the BS does not necessarily have enough up-to-date information about the current state of the connections at the subscriber station. In this paper, we propose a preemption-based scheduling algorithm that focuses on improving the quality of service requirements of real-time service flow classes. The proposed algorithm incorporates two schedulers, one at the BS and another one at the subscriber station. We have implemented and integrated the proposed algorithm with the network simulator NS2 using the Network and Distributed Systems Laboratory wireless interoperability of microwave access module. Simulation results have shown that the proposed approach outperforms other scheduling algorithms in terms of enhancing the throughput and the average delay of real-time quality of service classes. Copyright © 2013 John Wiley & Sons, Ltd.

The scheduling in the proposed algorithm is assisted by the subscriber stations, hence requiring two-schedulers, a scheduler at the BS and another one at the SS, where preemption is applied to both. The bandwidth is dynamically distributed among service flows while giving real-time packets more chances to satisfy their latency QoS requirement. As a result, the average end-to-end delay for these packets increases at the beginning then decreases to a stable value while maintaining the QoS requirements of other classes.

Many mobile devices (e.g., smart phones, PDAs, portable computers) and wireless routers (e.g., WiFi access points) nowadays are equipped with ad hoc transmission mode. In a dense environment such as a college/office campus, this creates the possibility of forming a wireless mesh network (WMN) in which mobile users communicate with each other through multiple wireless hops. This allows mobile users to exchange (share) files over the free access WMN rather than a carrier frequency such as 3G and WiMax. We consider a peer-to-peer (P2P) content sharing setting in a WMN, wherein the mesh network operator over-provision a number of mesh routers in the network with additional storage capacity and P2P-aware devices that are programmed to cache and store P2P content. Those mesh routers act as caches and participants in P2P content sharing. The aim of this setting is to both reduce the cost of communications between peers within the WMN (i.e., reduce bandwidth and energy that P2P traffic consumes in the network), and enhance the performance of P2P content sharing (i.e., reduce the average P2P content download delay). Our main contribution in this paper is an optimum P2P content replication strategy at the participating mesh routers. In particular, we determine the optimum number of replicas for every P2P file such that the average access cost of all files in the network is minimized. We propose a centralized algorithm that enables the participating mesh routers to implement the optimal strategy. We further propose a distributed (low cost) algorithm for P2P content replication at the participating mesh routers, and show that the distributed algorithm mimics the optimal strategy very well. The analytical and simulation results show that our replication strategy significantly reduces the average overall cost of accessing P2P files in the WMN as compared with other commonly used replication strategies. Copyright © 2013 John Wiley & Sons, Ltd.

Our main contribution in this paper is an optimum strategy that replicates P2P files at a number of mesh routers in the wireless mesh network, which participate in the P2P content sharing service. In particular, we determine the optimum number of replicas for every P2P file such that the average access cost of all P2P files in the network is minimized. We propose centralized and distributed algorithms that enable the participating mesh routers to implement the optimal strategy.

This paper proposes a power allocation scheme to maximize the sum capacity of all users for signal-to-leakage-and-noise ratio (SLNR) precoded multiuser multiple-input single-output downlink. The designed scheme tries to explore the effect of the power allocation for the SLNR precoded multiuser multiple-input single-output system on sum capacity performance. This power allocation problem can be formulated as an optimization problem. With high signal-to-interference-plus-noise ratio assumption, it can be converted into a convex optimization problem through the geometric programming and hence can be solved efficiently. Because the assumption of high signal-to-interference-plus-noise ratio cannot be always satisfied in practice, we design a globally optimal solution algorithm based on a combination of branch and bound framework and convex relaxation techniques. Theoretically, the proposed scheme can provide optimal power allocation in sum capacity maximization. Then, we further propose a judgement-decision algorithm to achieve a trade-off between the optimality and computational complexity. The simulation results also show that, with the proposed scheme, the sum capacity of all the users can be improved compared with three existing power allocation schemes. Meanwhile, some meaningful conclusions about the effect of the further power allocation based on the SLNR precoding have been also acquired. The performance improvement of the maximum sum capacity power allocation scheme relates to the transmit antenna number and embodies different variation trends in allusion to the different equipped transmit antenna number as the signal-to-noise ratio (SNR) changes.Copyright © 2013 John Wiley & Sons, Ltd.

We propose a power allocation scheme to maximize the sum capacity of all users for signal-to-leakage-and-noise ratio precoded multiuser multiple-input single-output downlink. Considering the trade-off between the computational complexity and the optimality, in the proposed judgement-decision algorithm, the power allocation problem is first formulated as a nonlinear nonconvex optimization problem, and then solved by a combination of branch and bound framework and convex relaxation technique in general while by geometric programming in some special channel cases.

The adaptive modulation and coding (AMC) technique, which has been adopted by advanced mobile telecommunication systems, supports a flexible response to the random radio behaviour. As a result, the attained transmission rate over a wireless link is time varying. Hence, resource demands are not deterministic but fluctuating even for calls with constant bit rate service requirements. Consequently, constant bit rate calls are susceptible to a forced call termination because of insufficient resources not only in a target cell during inter-cell handoffs but also in a serving cell during radio link deterioration. Furthermore, call blocking and dropping probabilities depend on radio propagation conditions among other factors and therefore they are dissimilar throughout a service area. The latter leads to unfairness problems. We analytically measure the impact of AMC on fixed-rate service with hard delay constraints such as voice for different signal, mobility and traffic conditions. We consider a reference case (call requests are admitted into the system provided there are enough free resources) and two classes of admission control approaches: traditional (only inter-cell handoffs are prioritised) and modified (all ongoing calls are prioritised). The reported results reveal conditions for which AMC affects voice call performance and can serve as guidelines on admission control design. Copyright © 2013 John Wiley & Sons, Ltd.

We analytically measure the impact of adaptive modulation and coding on calls with constant bit rate service requirements. The numerical results show that for realistic conditions, the fluctuating wireless radio link and the resultant dynamic resource demand can deteriorate call performance. Furthermore, if handoff calls are prioritised but active calls that experience radio link deterioration and hence require additional resources are not treated differentially, call interruptions are more frequent than those observed in a system without any admission control policy.

Recent advances in the field of wireless communication have proven the importance of diversity in combating channel fading and improving the bit error rates (BERs). In this report, a dual-hop decode-amplify-forward (DAF) transmission system over Nakagami-m fading channel is studied. The DAF relay system is a hybrid of decode-and-forward and amplify-and-forward relay systems that shows the benefits of both decode-and-forward and amplify-and-forward relay systems and is also called hybrid relay system or hybrid DAF relay system. Signal-to-noise ratios and BERs for various system models with varying number of transmit and receive antennas have been discussed. The diversity is achieved in two ways: firstly, by the use of relay and secondly, by the use of multiple antennas at both the transmitter and the receiver. Dual-hop relaying gives better trunking efficiency and with single antenna at the relay site acquisition and antenna structures are much less expensive. The variations in the performance levels when the relay is moved to different locations within the line of sight of the transmitter and the receiver have also been analyzed. BERs with respect to variations in the fading parameter ‘m’ have also been presented and discussed. Copyright © 2013 John Wiley & Sons, Ltd.

A hybrid dual-hop decode-amplify-forward relaying system over Nakagami-m fading channel has been proposed. The system improves the performance of the wireless system in terms of bit error rates by exploiting diversity introduced by a low-complexity transceiver node adaptive to various communication models and different fading conditions.

To realize high-speed communication, broadband transmission has become an indispensable technique in the next-generation wireless communication systems. Broadband channel is often characterized by the sparse multipath channel model, and significant taps are widely separated in time, and thereby, a large delay spread exists. Accurate channel state information is required for coherent detection. Traditionally, accurate channel estimation can be achieved by sampling the received signal with large delay spread by analog-to-digital converter (ADC) at Nyquist rate and then estimate all of channel taps. However, as the transmission bandwidth increases, the demands of the Nyquist sampling rate already exceed the capabilities of current ADC. In addition, the high-speed ADC is very expensive for ordinary wireless communication. In this paper, we present a novel receiver, which utilizes a sub-Nyquist ADC that samples at much lower rate than the Nyquist one. On the basis of the sampling scheme, we propose a compressive channel estimation method using Dantzig selector algorithm. By comparing with the traditional least square channel estimation, our proposed method not only achieves robust channel estimation but also reduces the cost because low-speed ADC is much cheaper than high-speed one. Computer simulations confirm the effectiveness of our proposed method. Copyright © 2013 John Wiley & Sons, Ltd.

We present a novel receiver that utilizes a sub-Nyquist analog-to-digital converter (ADC) that samples at much lower rate than the Nyquist one. On the basis of the sampling scheme, we propose a compressive channel estimation method using Dantzig selector algorithm. Comparing with the traditional least square channel estimation, our proposed method not only achieves robust channel estimation but also reduces the cost since low-speed ADC is much cheaper than high-speed one.

In a relay-assisted cellular network, the transmission mode (either direct transmission or relaying) and the transmit power of the source and relay nodes affect not only transmission rates of individual links but also the rates of other links sharing the same channel. In this paper, we propose a cross-layer design that jointly considers the transmission mode/relay node selection (MRS) with power allocation (PA) to optimize the system rate. We first formulate an optimization problem for a cellular system, where the same frequency channel can be reused in different cells. A low complexity heuristic MRS scheme is proposed on the basis of the link and interference conditions of the source and potential relay nodes. Given the transmission mode and relay node (if the relaying mode is chosen) of each link, the transmit power of the source and relay nodes can be solved by geometric programming. This method for MRS and PA can achieve a close-to-optimum performance, but implementing the PA requires heavy signalling exchanged among cells. To reduce the signalling overheads, we finally proposed a heuristic and distributed method for MRS and PA inspired by some asymptotic analysis. Numerical results are conducted to demonstrate the rate performance of the proposed methods.Copyright © 2013 John Wiley & Sons, Ltd.

The problem of the transmission mode/route selection (MRS) and power allocation (PA) is studied in an interferencelimited relay-assisted wireless cellular network. A heuristic MRS scheme is designed by considering the link conditions and co-channel interference. An optimization problem for PA for the given MRS is then solved using the geometric programming method. To reduce the signalling overheads among cells for PA, we accordingly proposed a heuristic and distributed method on the basis of some asymptotic analysis.

In long-term evolution, the service area is partitioned into several tracking areas (TAs), which comprise one or more cells (the radio coverages of base stations). The TAs are grouped into TA list (TAL). When an incoming call arrives, the network attempts to connect to the user equipment (UE) by paging the cells in the UE's TAL, which may incur large paging traffic that significantly consumes the limited radio resources. To resolve this issue, this paper proposes a dynamic paging scheme that determines the paging sequence of cells in real time according to the UE movement and call behavior. We compare the performance of the dynamic paging with that of the previously proposed Cell-TA-TAL (CTT) paging. Our study indicates that the dynamic paging outperforms the CTT paging when movement pattern is regular and the UE moves frequently. Copyright © 2013 John Wiley & Sons, Ltd.

This paper proposes a dynamic paging scheme that determines the paging sequence of cells in real time according to the user equipment movement and call behavior. We compare the performance of the dynamic paging with that of the previously proposed Cell-tracking area (TA)-TA list (CTT) paging. Our study indicates that the dynamic paging outperforms the CTT paging when movement pattern is regular and the user equipment moves frequently.

In wireless sensor networks, data aggregation protocols are used to prolong the network lifetime. However, the problem of how to perform data aggregation while preserving data privacy is challenging. This paper presents a polynomial regression-based data aggregation protocol that preserves the privacy of sensor data. In the proposed protocol, sensor nodes represent their data as polynomial functions to reduce the amount of data transmission. In order to protect data privacy, sensor nodes secretly send coefficients of the polynomial functions to data aggregators instead of their original data. Data aggregation is performed on the basis of the concealed polynomial coefficients, and the base station is able to extract a good approximation of the network data from the aggregation result. The security analysis and simulation results show that the proposed scheme is able to reduce the amount of data transmission in the network while preserving data privacy. Copyright © 2013 John Wiley & Sons, Ltd.

This paper presents a polynomial regression-based data aggregation protocol that preserves the privacy of sensor data. The security analysis and simulation results show that the proposed scheme is able to reduce the amount of data transmission in the network while preserving data privacy.

In our previous work, the limitation of standard type I and II power saving in IEEE 802.16e was discussed, and the idea of load-based power saving (LBPS) was proposed for better power-saving efficiency. LBPS measures traffic load and adaptively generates proper sleep schedule for the current load. Three LBPS schemes have been proposed for mobile subscriber station (MSS) power saving. In this paper, base station (BS) power saving is taken into consideration, and our previously proposed LBPS schemes, are extended and revised to integrate both BS and MSS in sleep scheduling. Two strategies of integrated power saving, MSS first and BS first, each with associated LBPS schemes are proposed in the paper. A three-staged concept combining the proposed strategies is also presented to make the best of integrated power saving. A simulation study shows that the proposed schemes can effectively achieve high power-saving efficiency for both BS and MSS. Copyright © 2013 John Wiley & Sons, Ltd.

The sleep schedule for each (MSS is first determined in LBPS-S1. The time frames in which all MSSs in the sleep mode are scheduled are the sleep time frames for BS. LBPS-aggr presents the simplest case among the LBPS schemes for BS power saving because all MSSs are treated as a single group.

Latest regulations on TV white space communications and trend toward spectrum access through geolocation databases relax the regulatory constraints on cognitive radios. Radio environment map (REM) is a kind of improved geolocation database and an emerging topic with the latest regulations on TV white space communications. It constructs a comprehensive temperature map of the cognitive radio network operation area by utilizing multi-domain information from geolocation databases, characteristics of spectrum use, geographical terrain models, propagation environment, and regulations. REMs act as cognition engines by building long-term knowledge via processing spectrum measurements collected from sensors to estimate the state of locations without any measurement data. Active transmitter LocatIon Estimation based REM construction technique is proposed and compared with the well-known REM construction techniques such as Kriging and inverse distance weighted interpolation in shadow and multipath fading channels. The simulation results suggest that the LocatIon Estimation based REM construction outperforms the compared methods in terms of RMSE and correct detection zone ratio by utilizing additional information about channel parameters that can be estimated by classical least squares method easily.Copyright © 2013 John Wiley & Sons, Ltd.

Active transmitter LocatIon Estimation based radio environment map (REM) construction technique is proposed and compared with the well-known REM construction techniques in shadow and multipath fading channels. The simulation results suggest that the LocatIon Estimation based REM construction outperforms the compared methods in terms of root-mean-square error and correct detection zone ratio.

In this paper, we study joint beamforming and power control for downlink multiple-input multiple-output systems with multiple users and target values for signal-to-interference plus noise ratios (SINRs). We formulate this as a constrained optimization problem of minimizing total interference subject to constraints on the beamforming vector norms, target SINRs, and total transmit power. Necessary and sufficient conditions satisfied by the optimal beamformer and power allocation are presented, and a new algorithm for joint beamforming and power control is proposed. This adapts the beamforming vectors and transmit powers incrementally, and it stops when the specified SINR targets are achieved with minimum powers. The proposed algorithm is illustrated with numerical results obtained from simulations, which study its convergence and compare it with other similar algorithms. Copyright © 2013 John Wiley & Sons, Ltd.

In this paper, we study joint beamforming and power control for downlink multiple-input multiple-output systems with multiple users and target values for signal-to-interference plus noise ratios. We formulate this as a constrained optimization problem, discuss necessary and sufficient conditions, and propose a new algorithm for joint beamforming and power control. The proposed algorithm is illustrated with numerical results obtained from simulations, which study its convergence properties and compare it with other similar algorithms.

Groups of people with mobile phones using short-range connections such as WiFi and Bluetooth to propagate messages can be modeled as, with regard to regular absence of end-to-end connection, mobile social networks (MSNs), which can be exploited to offload a significant amount of mobile content from the overloaded infrastructure networks such as 3G. The study of content transmission delay for the applications of mobile content dissemination in MSNs is an important problem, because to enhance the network capacity, the traffic is offloaded at the cost of inducing longer delay. In contrast to existing works, which ignore the factors of contact duration limits and large content size, we present a contact duration aware framework to model the content dissemination process in MSNs, give an explicit expression for the average content dissemination delay, and reveals its relationship with various system parameters of content size, users’ selfishness, number of involved subscribers, infecting ratio, and so on. We apply our proposed model to real-life traces to assess its reliability by comparing the theoretical results with measured statistics and present extensive upshots to evaluate the influence of various parameters on system performance. The results demonstrate the accuracy of our proposed framework and reveal that system parameters of content size, system infecting ratio and intragroup transmission are the most important factors to influence the content dissemination delay. Copyright © 2013 John Wiley & Sons, Ltd.

In this work, we present a contact duration aware framework to model the content dissemination process in mobile social networks. We apply our proposed model to real-life traces to assess its reliability by comparing the theoretical results with measured statistics and present extensive upshots to evaluate the influence of various parameters on system performance. The results demonstrate the accuracy of our proposed framework and reveal that system parameters of content size, system infecting ratio and intra-group transmission are the most important factors to influence the content dissemination delay.

We consider the problem of cooperative spectrum sharing among primary users (PUs) and secondary users (SUs) in cognitive radio networks. In our system, each PU selects a proper set of SUs to serve as the cooperative relays for its transmission and in return, leases portion of channel access time to the selected SUs for their own transmission. PU decides how to select SUs and how much time it would lease to SUs, and the cooperative SUs decide their respective power levels in helping PU's transmission, which are proportional to their access times. We assume that both PUs and SUs are rational and selfish. In single-PU scenario, we formulate the problem as a noncooperative game and prove that it converges to a unique Stackelberg equilibrium. We also propose an iterative algorithm to achieve the unique equilibrium point. We then extend the proposed cooperative mechanism to a multiple-PU scenario and develop a heuristic algorithm to assign proper SUs to each PU considering both performance and fairness. The simulation results show that when the competition among SUs is fierce, the performance gap between our heuristic algorithm and the optimal one is smaller than 3%. Copyright © 2013 John Wiley & Sons, Ltd.

We discuss the problem of cooperative spectrum sharing among primary users (PUs) and secondary users (SUs). In the single-PU scenario, we assume that SUs’ access opportunities are positive correlated to their cooperative power levels and prove that the unique Stackelberg equilibrium exists. In the multiple-PU scenario, we develop a heuristic mechanism to direct PUs about how to recruit the relay candidates considering both performance and fairness, how to choose the proper relays and how to allocate the frames.

The universal mobile telecommunications system (UMTS) and long term evolution (LTE)/LTE-advanced specifications have been proposed to offer high data rate for the forwarding link under high-mobility wireless communications. The keys include supporting multi-modes of various coding schemes (e.g., VSF-OFCDM, OFDM, OFDMA), multiple-input multiple-output, relay networks, and so on. To balance loads among different communication interfaces is one of the most important issues that should be addressed for achieving efficient radio resource allocations. In a shared packet service, the 3GPP UMTS adopts the VSF-OFCDM interface to allocate orthogonal codes of an OVSF code tree in two-dimension (2D) spreading at the time and frequency domains. However, it easily leads to high packet loss rate and high bandwidth waste rate, because it does not consider interference and the adaptive modulation and coding scheme simultaneously. Conversely, although the LTE/LTE-advanced interface offers a high data rate, it suffers from unbalanced loads and moderate reward. This paper thus proposes an adaptive radio resource allocation for balancing loads between the UMTS and LTE/LTE-advanced interfaces according to various interference and mobility environments. In addition, an adaptive multi-code allocation is proposed for the UMTS to minimize the bandwidth waste rate while guaranteeing quality of service. Numerical results indicate that the proposed approach outperforms other approaches in fractional reward loss and system utilization. Copyright © 2013 John Wiley & Sons, Ltd.

The universal mobile communications system (UMTS) and long term evolution (LTE)/LTE-Advanced specifications have been proposed to offer high data rate for the forwarding link under high-mobility wireless communications. An adaptive radio resource allocation for balancing loads between the UMTS and LTE/LTE-Advanced interfaces according to various interference and mobility environments is proposed. Moreover, an adaptive multi-code allocation is proposed for the UMTS to minimize the bandwidth waste rate while guaranteeing quality of service.

Cooperative spatial multiplexing (CSM) system has played an important role in wireless networks by offering a substantial improvement in multiplexing gain compared with its cooperative diversity counterpart. However, there is a limited number of research works that consider the performance of CSM systems. As such, in this paper, we have derived exact performance of CSM with amplify-and-forward and decode-and-forward relays in terms of outage capacity and ergodic capacity. We have shown that CSM systems yield a unity diversity order regardless of the number of antennas at the destination and the number of relays in the networks, which is the direct result of diversity and multiplexing gain trade-off. Our analytical expressions are corroborated by Monte-Carlo simulations. Copyright © 2013 John Wiley & Sons, Ltd.

As such, in this paper, we have derived an exact performance of CSM with amplify-and-forward and decode-and-forward relays in terms of outage capacity and ergodic capacity.

In this paper, we propose symbol-based receivers for orthogonal frequency division multiplexing (OFDM) code-division multiple-access (CDMA) multiple-input-multiple-output (MIMO) communications in multipath fading channels. For multiuser and multipath fading environments, both intersymbol interference and multiple-access interference must be considered. We propose narrowband and wideband antennas and Wiener code filter for MIMO OFDM-CDMA systems. The proposed receivers are updated symbol-by-symbol to achieve low computational complexity. Simulation results show that the proposed Wiener code filter can improve the system performance for the proposed adaptive antennas. The wideband antenna can achieve better error-rate performance than that of the narrowband antenna when multipath effect exists. The convergence rate of the recursive least squares antennas is faster than that of the least mean square antennas. Copyright © 2013 John Wiley & Sons, Ltd.

In this paper, we propose narrowband and wideband antennas and Wiener code filter for multiple-input-multiple-output orthogonal frequency division multiplexing (OFDM) code-division multiple-access systems. The proposed receivers are updated symbol-by-symbol to achieve low computational complexity. Simulation results show that Wiener code filter can improve the system performance for the proposed adaptive antennas. The wideband antenna can achieve better error-rate performance than narrowband antenna once the multipath effect exists.

In this paper, we propose a novel scheme of how to efficiently and reliably deliver multimedia real-time streams in wireless sensor networks. To specify the property of streams, a multimedia stream is modeled as an (m,k)-firm stream that is known to have the characteristics of weakly hard real-time system. In addition, a distributed, measurement-based routing scheme for (m,k)-firm streams is newly proposed while considering several constraints on node as well as on communication medium. Simulations and their analysis are provided to validate the suitability of traffic modeling, reduced dynamic failure probability, and extended network lifetime when the proposed routing protocol is employed. Copyright © 2013 John Wiley & Sons, Ltd.

In this paper, we propose a novel scheme of how to efficiently and reliably deliver multimedia real-time streams in wireless sensor networks. To specify the property of streams, a multimedia stream is modeled as an (m,k)-firm stream that is known to have the characteristics of weakly hard real-time system. In addition, a distributed, measurement-based routing scheme for (m,k)-firm streams is newly proposed while considering several constraints on node as well as on communication medium. Simulations and their analysis are provided to validate the suitability of traffic modeling, reduced dynamic failure probability, and extended network lifetime when the proposed routing protocol is employed.

Network coding (NC) is a technique that allows intermediate nodes to combine the received packets from multiple links and forwarded to subsequent nodes. Compared with pure relaying, using NC in a wireless network, one can potentially improve the network throughput, but it increases the complexity of resource allocations as the quality of one transmission is often affected by the transmission conditions of multiple links. In this paper, we consider an ad hoc network, where all the links have bidirectional communications, and a relay node forwards traffic between the source and the destination nodes using NC. All transmissions share the same frequency channel, and simultaneous transmissions cause interference to each other. We consider both digital NC and analog NC strategies, referred to as DNC and ANC, respectively, and schedule transmission time and power of the nodes in order to maximize the overall network throughput. For DNC, an optimum scheduling is formulated and solved by assuming that a central controller is available to collect all the link gain information and make the scheduling decisions. Distributed scheduling schemes are proposed for networks using DNC and ANC. Our results indicate that the proposed scheduling scheme for DNC achieves higher throughput than pure relaying, and the scheduling scheme for ANC can achieve higher throughput than both DNC and pure relaying under certain conditions. Copyright © 2013 John Wiley & Sons, Ltd.

This paper studies transmission power allocations and time scheduling in an ad hoc network with bidirectional communication links and using network coding. All transmissions use the same frequency channel. Both digital and analog network codings are considered. Distributed scheduling and power allocations schemes are proposed. Numerical results show that much higher throughput can be achieved using digital network coding or analog network coding and the proposed schemes, compared with optimum time scheduling and power allocations using pure relaying.

In designing cognitive radio systems, one of the most critical issues is handling the channel handover process (CHP). The CHP consists of spectrum sensing, spectrum decision, negotiation on the common control channel, and adjustment of frequency and modulation settings, and such, it can be a time-consuming process. Consequently, initiating the CHP after each detected user activity (UA) can decrease the aggregate spectrum utilization. To alleviate this problem, we introduce a novel handover strategy to find the optimal trade-off between the durations of the CHP and UAs. With the use this model, secondary users (SUs) track only local information on their current data channel to make the decision to initiate the CHP or to wait for the termination of the ongoing UA. The system adapts to the dynamic conditions of the data channels and reduces the frequency of handovers to increase throughput and decrease access delay. We give analytical utilization bounds for SUs and also compare the performance of our model to those of other channel handover strategies by using extensive simulations. Our results for channels with heterogeneous loads and dynamic environments show that this model can clearly decrease the frequency of handover and consequently increase the aggregate SU utilization. Copyright © 2013 John Wiley & Sons, Ltd.

The channel handover process (CHP) in cognitive radio networks is a time-consuming process. We introduce a novel handover strategy to find the optimal trade-off between the durations of the CHP and the user activities. Secondary users are tracking only local information to make the decision to initiate the CHP or waiting the termination of the ongoing user activity. The system adapts to the dynamic conditions of the channels and increases the throughput by reducing the frequency of handovers.

The mobile tactical network is a practical implementation of the mobile ad hoc network. Formed across tactical radios operating in the military very high frequency and low ultrahigh frequency bands, the mobile tactical network has distinctive characteristics when compared with generic mobile ad hoc networks, in particular with respect to its network topological behaviors and connectivity attributes. These characteristics must be understood and considered when selecting suitable network protocols. To this end, in this paper, a network science-based systematic modeling approach is applied to analyze typical deployment scenarios and identify fundamental tactical network properties. The novel framework employs realistic scenario models as well as radio physical layer performance parameters and channel models to effectively capture the dynamic network behavior that needs to be considered for protocol design. The results provide critical insights and guidance to the development of tactical network solutions. © Her Majesty the Queen in Right of Canada 2013

The mobile tactical network is a practical implementation of the mobile ad hoc network. Formed across tactical radios operating in the military very high frequency and low ultrahigh frequency bands, mobile tactical networks have distinctive characteristics when compared with generic mobile ad hoc networks. Taking a novel network science-based systematic modeling approach, this work analyzes typical deployment scenarios using realistic radio and network parameters to identify the fundamental tactical network topological properties and dynamic behaviors.

A small device-based, low-rate, short-range wireless radio communication often hampers high reliability in wireless sensor networks. However, more applications are increasingly demanding high reliability. For this requirement to be met, various approaches have been proposed in a layered manner. Among those, MintRoute is a well-known network layer approach to develop a new metric based on link quality for path selection toward the sink. By choosing the link with the highest measured value, the proposed approach can afford a higher possibility to transmit a packet over the link without error. However, there are still several issues to be discussed during operations. In this paper, we propose how to improve the MintRoute protocol through several revised algorithms, including the development of a new metric, a parent selection considering distance and level from the sink node, and a fast recovery method against failures. Simulations and analysis are performed to validate the suitability of reduced end-to-end delay and fast recovery from failures.Copyright © 2013 John Wiley & Sons, Ltd.

In this paper, we propose how to improve the MintRoute protocol through several revised algorithms, including the development of a new metric, a parent selection considering distance and level from the sink node, and a fast recovery method against failures.

Errors encountered in digital wireless channels are not independent but rather form bursts or clusters. Error models aim to investigate the statistical properties of bursty error sequences at either packet level or bit level. Packet-level error models are crucial to the design and performance evaluation of high-layer wireless communication protocols. This paper proposes a general design procedure for a packet-level generative model based on a sampled deterministic process with a threshold detector and two parallel mappers. In order to assess the proposed method, target packet error sequences are derived by computer simulations of a coded enhanced general packet radio service system. The target error sequences are compared with the generated error sequences from the deterministic process-based generative model using some widely used burst error statistics, such as error-free run distribution, error-free burst distribution, error burst distribution, error cluster distribution, gap distribution, block error probability distribution, block burst probability distribution, packet error correlation function, normalized covariance function, gap correlation function, and multigap distribution. The deterministic process-based generative model is observed to outperform the widely used Markov models.Copyright © 2013 John Wiley & Sons, Ltd.

The paper proposes a general design procedure for a packet-level generative model based on a sampled deterministic process with a threshold detector and two parallel mappers. A coded enhanced general packet radio service system is utilized to obtain target packet error sequences for parameterization and comparison purposes. It is shown that the proposed deterministic process-based generative model can generate error sequences with accurate burst error statistics and outperform the widely used Markov models.

Wireless sensor networks (WSNs) have found a wide variety of applications recently. However, the challenges in WSNs still remain in improving the sensor energy efficiency and information quality (distortion reduction) of the sensing data transmissions. In this paper, we propose a novel cross-layer design of resource allocation and channel coding to protect distributed source coding (DSC)-based data transmission. Resource allocation strategies include rate adaptation and automatic repeat-request retransmissions. Our proposed joint design of resource allocation, channel coding, and DSC can improve the network energy efficiency and information quality while meeting the data transmission latency requirements. Further, we investigate how the resource allocation enables the network to achieve unequal error protection among correlated DSC streams. Our simulation studies demonstrate that the proposed joint design significantly improves the DSC-based data transmission quality and the network energy efficiency. Copyright © 2013 John Wiley & Sons, Ltd.

In this paper, we propose a novel cross-layer design of resource allocation and channel coding to protect distributed source coding-based data transmission. Our proposed joint design of resource allocation, channel coding, and distributed source coding can improve the network energy efficiency and information quality while meeting the data transmission latency requirements.

We present intrusion detection algorithms to detect physical layer jamming attacks in wireless networks. We compare the performance of local algorithms on the basis of the signal-to-interference-plus-noise ratio (SINR) executing independently at several monitors, with a collaborative detection algorithm that fuses the outputs provided by these algorithms. The local algorithms fall into two categories: simple threshold that raise an alarm if the output of the SINR-based metrics we consider deviates from a predefined detection threshold and cumulative sum (cusum) algorithms that raise an alarm if the aggregated output exceeds the predefined threshold. For collaborative detection, we use the Dempster–Shafer theory of evidence algorithm. We collect SINR traces from a real IEEE 802.11 network, and with the use of a new evaluation method, we evaluate both the local and the Dempster–Shafer algorithms in terms of the detection probability, false alarm rate, and their robustness to different detection threshold values, under different attack intensities. The evaluation shows that the cusums achieve higher performance than the simple threshold algorithms under all attack intensities. The Dempster–Shafer algorithm when combined with the simple algorithms, it can increase their performance by more than 80%, but for the cusum algorithms it does not substantially improve their already high performance.Copyright © 2013 John Wiley & Sons, Ltd.

The evaluation shows that the cusums achieve higher performance than simple threshold algorithms under all attack intensities. The Dempster-Shafer algorithm, when combined with the simple algorithms, can increase their performance by more than 80%, but for the cusum algorithms, it does not substantially improve their already high performance.

In this paper, we address the problems of power scheme and time-division bargaining under the mode of cooperative transmission in cognitive networks. Cognitive relay communication has been regarded as an effective method to solve the problem of the coexistence for cognitive users in a primary system. It is understandable that the cognitive users who have helped primary users communicate may be permitted to use the spectrum partly or timely where the problems of identifying the interference level and time division should be taken into account. In the underlay mode, we analyze the impact of dynamic interference temperature and give the relevant presentations in detail for its influence on the secondary user. In the overlay mode, we resolve the key problem of time division, which influences the benefit allocation between participants, by using game theory, which is a helpful tool for solving various problems of resource allocation in wireless networks. Furthermore, numerical results are presented to show that the proposed approach has better and encouraging effects. Copyright © 2013 John Wiley & Sons, Ltd.

The method of cooperative communication between primary and cognitive users has provided an effective solution to improve the real coexistence between them. The authors investigate the resource allocation involved in the cooperation based on the dynamic spectrum leasing.

Energy efficiency is one of the top priorities for future cellular networks, which could be accomplished by implementing cooperative mechanisms. In this paper, we propose three evolved node B (eNB)-centric energy-saving cooperation techniques for long-term evolution (LTE) systems. These techniques, named as intra-network, inter-network, and joint cooperation, involve traffic-aware intelligent cooperation among eNBs belonging to the same or different networks. Our proposed techniques dynamically reconfigure LTE access networks in real time utilizing less number of active eNBs and thus, achieve energy savings. In addition, these techniques are distributed and self-organizing in nature. Analytical models for evaluating switching dynamics of eNBs under these cooperation mechanisms are also formulated. We thoroughly investigate the proposed system under different numbers of cooperating networks, traffic scenarios, eNB power profiles, and their switching thresholds. Optimal energy savings while maintaining quality of service is also evaluated. Results indicate a significant reduction in network energy consumption. System performance in terms of network capacity utilization, switching statistics, additional transmit power, and eNB sleeping patterns is also investigated. Finally, a comprehensive comparison with other works is provided for further validation. Copyright © 2013 John Wiley & Sons, Ltd.

In this paper, we propose three different evolved node B (eNB)-centric energy-saving cooperation techniques for LTE systems. These techniques, named as intra-network, inter-network, and joint cooperation, involve traffic-aware intelligent cooperation among eNBs belonging to the same or different networks. Analytical models for modeling the switching dynamics of eNBs under these cooperation mechanisms are also formulated. Results indicate a significant reduction in network energy consumption. Furthermore, a comprehensive comparison with other research is also provided for further validation.

Slotted ALOHA is a simple and straightforward random multiple access technique, which has been used extensively in data and cellular networks as the protocol for random access. The complexity of state space-based analysis methods for finite user finite buffer systems increases exponentially with buffer size and number of users. The presence of multipath frequency selective fading channel further adds to the complexity, making the analysis practically intractable. This paper uses an approximate analysis technique called tagged user analysis (TUA) to analyze the performance parameters of slotted ALOHA over multipath and frequency selective fading channels for finite user finite buffer systems. In TUA, the steady state system performance is evaluated from the analysis of a single user. Moreover, the state flow graph of TUA has just four states, thus reducing the complexity of the analysis. Simulation results confirm the validity of the TUA analysis. Copyright © 2013 John Wiley & Sons, Ltd.

This paper uses an approximate analysis technique called tagged user analysis (TUA) to analyze the quality of service parameters of slotted ALOHA over multipath and frequency selective fading channels for finite user finite buffer systems. In TUA, the steady state system performance is evaluated from the analysis of a single user. Moreover, the state flow graph of TUA has just four states, thus reducing the complexity of the analysis.

It is well known that conventional rate-compatible (RC) codes, such as Raptor codes, only perform well at long code lengths. However, we propose a class of RC codes with short code lengths in this paper. Particularly, we develop a computational approach to design online-generated RC low-density parity-check (LDPC) codes available on noisy channels. We first propose a diagonal-tailed encoding to generate Quasi-regular low-density generator matrix codes. Then, an optimal encoding profile for RC codes is achieved with a linear interpolation approach that is based on the fixed-rate quasi-regular LDPC codes. Finally, we evaluate the rateless and fixed-rate performances of the proposed RC codes by extensive simulation results on various code rates with different modulations.Copyright © 2013 John Wiley & Sons, Ltd.

We propose a class of rate-compatible (RC) codes with short lengths. Particularly, we develop a computational approach to design online-generated RC-LDPC codes on noisy channels. We first propose a diagonal-tailed encoding to generate quasi-regular low-density generator matrix codes. Then, an optimal encoding profile for RC codes is achieved by a linear interpolation approach. Finally, we evaluate the rateless and fixed-rate performances of the proposed RC codes by extensive simulation results on various code rates with different modulations.

Two-path or successive relaying, which aims to establish two relay links transmitting different information symbols in adjacent time slots, has recently emerged as an attractive wireless communication protocol to improve the spectral efficiency in half-duplex cooperative systems. In this paper, we investigate power allocation and relay selection techniques for amplify-and-forward two-path successive relaying networks. Our approach is based on the maximization of the received SNR subject to a total power budget consumed by the source and the relay assisting this specific transmission. Two scenarios including with and without direct link are considered here. We show that the main problem has a closed-form solution and only requires a few amounts of feedback bits to be broadcasted. Numerical results reveal that the proposed approaches are more insensitive to the inter-relay interference and robust to channel estimation errors; meanwhile, they perform better than the existing schemes. Copyright © 2013 John Wiley & Sons, Ltd.

We developed the power allocation and relay selection techniques for amplify-and-forward two-path successive relaying networks with two scenes: when the direct link exists or not. We show that with the same channel conditions, more power should be assigned to the source compared with the results in conventional one-path relaying networks. Relay selection can be implemented by selecting the relay with which a maximum received signal-to-noise ratio will be achieved and broadcasting the index of the relay as well as the normalized power value.

To utilize spectrum resources more efficiently, dynamic spectrum access attempts to allocate the spectrum to users in an intelligent manner. Uncoordinated sharing with cognitive radio (CR) users is a promising approach for dynamic spectrum access. In the uncoordinated sharing model, CR is an enabling technology that allows the unlicensed or secondary users to opportunistically access the licensed spectrum bands (belonging to the so-called primary users), without any modifications or updates for the licensed systems. However, because of the limited resources for making spectrum observations, spectrum sensing for CR is bound to have errors and will degrade the grade-of-service performance of both primary and secondary users. In this paper, we first propose a new partial spectrum sharing policy, which achieves efficient spectrum sharing between two licensed networks. Then, a Markov chain model is devised to analyze the proposed policy considering the effects of sensing errors. We also construct a cross-layer design framework, in which the parameters of spectrum sharing policy at the multiple-access control layer and the spectrum sensing parameters at the physical layer are simultaneously coordinated to maximize the overall throughput of the networks, while satisfying the grade-of-service constraints of the users. Numerical results show that the proposed spectrum sharing policy and the cross-layer design strategy achieve a much higher overall throughput for the two networks. Copyright © 2013 John Wiley & Sons, Ltd.

In this paper, we first propose a new partial spectrum sharing policy between two licensed networks. A Markov chain model is devised to analyze the proposed policy considering the effects of sensing errors. We also construct a cross-layer design framework, in which the parameters of spectrum sharing policy at the multiple-access control layer and the spectrum sensing parameters at the physical layer are simultaneously coordinated to maximize the overall throughput of the networks.

Opportunistic relaying in cooperative communication depends on careful relay selection. However, the traditional centralized method used for opportunistic amplify-and-forward protocols requires precise measurements of channel state information at the destination. In this paper, we adopt the max–min criterion as a relay selection framework for opportunistic amplify-and-forward cooperative communications, which was exhaustively used for the decode-and-forward protocol, and offer an accurate performance analysis based on exact statistics of the local signal-to-noise ratios of the best relay. Furthermore, we evaluate the asymptotical performance and deduce the diversity order of our proposed scheme. Finally, we validate our analysis by showing that performance simulation results coincide with our analytical results over Rayleigh fading channels, and we compare the max–min relay selection with their centralized channel state information-based and partial relay selection counterparts.Copyright © 2013 John Wiley & Sons, Ltd.

In this paper, we adopt the max-min criterion as a relay selection framework for opportunistic amplify-and-forward (AF) cooperative communications and offer an accurate performance analysis based on exact statistics of the local signal-to-noise ratios (SNRs) of the best relay. We validate our analysis by showing that performance simulation results coincide with our analytical results over Rayleigh fading channels, and we compare the max-min relay selection with their centralized channel state information-based and partial relay selection counterparts.

This paper considers multiaccess control for the uplink in orthogonal frequency division multiple access wireless networks. To avoid the extensive information exchange associated with centralized approaches, we formulate the decentralized access control problem with the contention power constraint as a Bayesian game, mapping time-varying channel state information into contention strategies. By exploiting the problem structure, a strategy where users access the channels with probability one if the observed channel gain is above a predetermined threshold is shown to be optimal. It is also shown that the energy consumption of the threshold strategy will not exceed that of randomized strategies. The game is then equivalently reformulated as one of finding the threshold value in a distributed manner, and the existence and uniqueness of Bayesian Nash equilibria is established. A distributed algorithm based on Lagrange duality is proposed to approach the unique equilibrium, and the algorithm is shown to be globally stable. In a homogeneous system, the performance loss of the proposed scheme is proved to be bounded compared with a centralized channel allocation scheme. Contrary to other proposals, our method allows for heterogeneous channel state information and achieves a comparable throughput with reduced power.Copyright © 2013 John Wiley & Sons, Ltd.

This paper studies uplink channel access with power constraint in orthogonal frequency-division multiple access networks by Bayesian game theoretic method. A distributed primal-dual algorithm is proposed to reach the Bayesian Nash equilibrium under heterogeneous channel state distribution, and its global stability is proven via Lyapunov stability theory. Its energy consumption and performance loss compared with centralized schemes are measured analytically by stochastic ordering theory.

In this paper,we consider a small-scale multipath fading channel following the α– μ generalized fading model distribution.We first derive an expression for the amount of fading () for this channel model to show the generalization attribute of this fading model recently reported in the literature. Then, we derive closed-form expressions for the average channel capacity considering this channel distribution under different adaptive transmission protocols, namely the simultaneous power and rate adaptation protocol, the optimal rate adaptation with fixed power protocol, and the channel inversion with fixed-rate protocol. All the obtained expressions are in closed-form and general expressions that can reduce to other channel capacity expressions that are well-known and to some others that are not known for Rayleigh, Nakagami-m, and Weibull, as special cases. The derived expressions in this paper are new and have not been previously reported in the literature.Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we consider the α– μ fading model and derive an expression for the amount of fading, and we also derive closed-form expressions for the average channel capacity considering this channel distribution under different adaptive transmission protocols, namely, the simultaneous power and rate adaptation protocol, the optimal rate with fixed power protocol, and the channel inversion with fixed rate protocol. Monte-Carlo simulations are also provided showing a great match with the numerical ones.

This paper presents a study on multicast communications in cognitive radio networks (CRNs)using directional antennas. The objective is to maximize the throughput of the CRN. The spectrum is divided into multiple channels and licensed to the primary network. While the CRN is accessing the spectrum, the interference power is carefully controlled to avoid impacting the operation of the primary network. The mathematical model is presented and subsequently formulated as a mixed integer non-linear programming (MINLP) problem, which is non-deterministic polynomial-time hard. Therefore, a greedy algorithm is designed to approximate the optimal performance. The MINLP problem is then relaxed and an upper bound is developed. Simulation results are presented to compare the performance of the greedy algorithm and the upper bound, which demonstrates the efficacy of the greedy algorithm as well as the tightness of the upper bound. Copyright © 2012 John Wiley & Sons, Ltd.

This paper presents a comprehensive study on how cognitive radio networks can utilize directional antennas to enhance throughput performance within multicast scenarios. A mixed integer non-linear programming (MINLP) problem is formulated to optimize the overall throughput of the cognitive radio networks. Because MINLP problem is NP-hard, a lightweight greedy algorithm is developed to approximate the optimal performance. Extensive simulation results demonstrate that the proposed greedy algorithm yields close-to-optimal performance and outperforms the reformulationlinearization technique based scheme.

IEEE 802.16 network introduces a multimedia data scheduling service with different quality of service (QoS) requirements. The scheduling service manages transmission resources according to data types, satisfying the requirements of different connections or users. On the basis of the data types defined in the service, we discuss a normalized QoS metric for the multimedia connections in the paper. The QoS value of a connection can be determined just by three components: the data type of the connection, its desired resources, and its allocated resources. Then, we propose an optimum bandwidth allocation solution, which can maximize the utility of base station. Next, we propose a call admission control scheme utilizing the bandwidth allocation solution. In the scheme, the occupied resource of ongoing connections will be regulated for the entry admission of a new connection, without degrading the network performance and the QoS of ongoing connections. Finally, the simulation results confirm that the proposed scheme with the normalized QoS can achieve better trade-off between ongoing connections and new connections.Copyright © 2012 John Wiley & Sons, Ltd.

The proposed call admission control scheme considers the quality of service metric of connections from the view of application layer. Through regulating the occupied resource of ongoing connections, the better trade-off can be achieved between ongoing and new connections without degrading the network performance.

Following the wired network virtualization, virtualization of wireless networks becomes the next step aiming to provide network or infrastructure providers with the ability to manage and control their networks in a more dynamic fashion. The benefit of the wireless mobile network virtualization is a more agile business model where virtual mobile network operators (MNOs) can request and thus pay physical MNOs in a more pay-as-you-use manner. This paper presents some resource allocation algorithms for joint network virtualization and resource allocation of wireless networks. The overall algorithm involves the following two major processes: firstly, to virtualize a physical wireless network into multiple slices, each representing a virtual network, and secondly, to carry out physical resource allocation within each virtual network (or slice). In particular, the paper adopts orthogonal frequency division multiplexing (OFDM) as its physical layer to achieve more efficient resource utilization. Therefore, the resource allocation is conducted in terms of sub-carriers. Although the motivation and algorithm design are based on IEEE 802.16 or WiMAX networks, the principle and algorithmic essence are also applicable to other OFDM access-based wireless networks. The aim was to achieve the following design goals: virtual network isolation and resource efficiency. The latter is measured in terms of network throughput and packet delivery ratio. The simulation results show that the aforementioned goals have been achieved. Copyright © 2012 John Wiley & Sons, Ltd.

This paper presents some resource allocation algorithms for joint network virtualization and resource allocation of wireless networks. The aim is to achieve the following design goals: virtual network isolation and resource efficiency. The latter is measured in terms of network throughput and packet delivery ratio. The simulation results show that the aforementioned goals have been achieved.

Multiuser multiple-input multiple-output orthogonal frequency division multiple access (MIMO-OFDMA) is considered as the practical method to attain the capacity promised by multiple antennas in the downlink direction. However, the joint calculation of precoding/beamforming and resource allocation required by the optimal algorithms is computationally prohibitive. This paper proposes computationally efficient resource allocation algorithms that can be invoked after the precoding and beamforming operations. To support stringent and diverse quality of service requirements, previous works have shown that the resource allocation algorithm must be able to guarantee a specific data rate to each user. The constraint matrix defined by the resource allocation problem with these data rate constraints provides a special structure that lends to efficient solution of the problem. On the basis of the standard graph theory and the Lagrangian relaxation, we develop an optimal resource allocation algorithm that exploits this structure to reduce the required execution time. Moreover, a lower-complexity suboptimal algorithm is introduced. Extensive simulations are conducted to evaluate the computational and system-level performance. It is shown that the proposed resource allocation algorithms attain the optimal solution at a much lower computational overhead compared with general-purpose optimization algorithms used by previous MIMO-OFDMA resource allocation approaches. Copyright © 2012 John Wiley & Sons, Ltd.

This paper proposes computationally efficient resource allocation algorithms for multiuser multiple-input multiple-output orthogonal frequency division multiple access. On the basis of standard graph theory and Lagrangian relaxation, we develop optimal resource allocation algorithms that exploit a special structure in the constraint matrix to reduce the required execution time. It is shown that the proposed resource allocation algorithms attain the optimal solution at a much lower computational overhead compared with general-purpose optimization algorithms used by previous approaches.

The ubiquity of mobile devices has facilitated the prevalence of participatory sensing, whereby ordinary citizens use their private mobile devices to collect regional information and to share with participators. However, such applications may endanger the users' privacy by revealing their locations and trajectories information. Most of existing solutions, which hide a user's location information with a coarse region, are under k-anonymity model. Yet, they may not be applicable in some participatory sensing applications that require precise location information. The goals are seemingly contradictory: to protect a user's location privacy while simultaneously providing precise location information for a high quality of service. In this paper, we propose a method to meet both goals. Through selecting a certain number of a user's partners, it can protect the user's location privacy while providing precise location information. The user's trajectory privacy can be protected by constructing several trajectories that are similar to the user's trajectory in an interval time T. Finally, we utilize a new metric, called slope ratio, to evaluate the partners' selection algorithm that we proposed. Then, we measure the privacy level that the location and trajectory privacy protection mechanism (LTPPM) can achieve. The analysis and simulation results show that LTPPM can protect the user's location and trajectory privacy effectively and also provide a high quality of service in participatory sensing. Copyright © 2012 John Wiley & Sons, Ltd.

Location and trajectory privacy problems are the main obstacles to the success of participatory sensing. However, most of existing anonymous methods hide a user's location with a coarse region, which may reduce quality of services. Moreover, the disclosure of trajectory may also reveal the user's location. In this paper, subject to high quality of services, we propose to protect the user's location and trajectory privacy on the basis of equivalence classes formed by his or her partners and present a new metric, named slope ratio, to evaluate trajectory similarity.

Because of the wide range of applications, many geographic routing protocols have been proposed in three-dimensional (3D) wireless sensor networks. However, all the methods require assistance from a global positioning system (GPS), which is not always available. In this paper, we propose a method of constructing an axis-based virtual coordinate assignment in 3D wireless sensor networks (ABVCap_3D) that requires no GPS assistance. We also propose a routing protocol based on ABVCap_3D, which guarantees packet delivery in 3D networks. Using simulations, we evaluate the performance of ABVCap_3D routing and other well-known routing protocols, such as greedy-random-greedy routing, greedy-hull-greedy routing, and the routing based on axis-based virtual coordinate assignment in 2D wireless sensor networks (ABVCap routing). Simulations show that ABVCap_3D routing requires significantly relative lower cost for guaranteeing packet delivery in comparison with ABVCap routing. Simulations also demonstrate that ABVCap_3D routing ensures a moderate ratio for routing path length to the shortest (ideal) path length. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we propose a method of constructing an axis-based virtual coordinate assignment in 3D wireless sensor networks (ABVCap_3D) that requires no global positioning system assistance. We also propose a routing protocol based on ABVCap_3D (ABVCap_3D routing), which guarantees packet delivery in 3D networks. Simulations show that ABVCap_3D routing requires significantly relative lower cost for guaranteeing packet delivery in comparison with ABVCap routing.

Energy balancing is an effective technique in enhancing the lifetime of a wireless sensor network (WSN). Specifically, balancing the energy consumption among sensors can prevent losing some critical sensors prematurely due to energy exhaustion so that the WSN's coverage can be maintained. However, the heterogeneous hostile operating conditions—different transmission distances, varying fading environments, and distinct residual energy levels—have made energy balancing a highly challenging task. A key issue in energy balancing is to maintain a certain level of energy fairness in the whole WSN. To achieve energy fairness, the transmission load should be allocated among sensors such that, regardless of a sensor's working conditions, no sensor node should be unfairly overburdened. In this paper, we model the transmission load assignment in WSN as a game. With our novel utility function that can capture realistic sensors’ behaviors, we have derived the Nash equilibrium (NE) of the energy balancing game. Most importantly, under the NE, while each sensor can maximize its own payoff, the global objective of energy balancing can also be achieved. Moreover, by incorporating a penalty mechanism, the delivery rate and delay constraints imposed by the WSN application can be satisfied. Through extensive simulations, our game theoretic approach is shown to be effective in that adequate energy balancing is achieved and, consequently, network lifetime is significantly enhanced. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we model the transmission load assignment in WSN as a game. With our novel utility function that can capture realistic sensors’ behaviors, we have derived the Nash equilibrium (NE) of the energy balancing game. Most importantly, under the NE, while each sensor can maximize its own payoff, the global objective of energy balancing can also be achieved, and consequently, network lifetime is significantly enhanced. Moreover, by incorporating a penalty mechanism, the delivery rate and delay constraints imposed by the WSN application can be satisfied as well.

In amplify-and-forward (AF)-based cooperative spectrum sensing system, the bit-error-rate (BER) performance and detection probability will decrease because of the existence of channel estimation error. In this paper, the influence of channel estimation error on system performance is firstly deduced, and then, linear minimum mean-square error (LMMSE) channel estimation algorithm with filtering delay time-domain windowing (LMMSE-filtering-DTW) technique and modified singular value decomposition-based LMMSE algorithm are proposed to improve the channel estimation performance for code division multiple access system and orthogonal frequency division multiplexing system in AF cooperative scenario, respectively. Simulation results verify the effectiveness of the two proposed channel estimation algorithms in cooperative spectrum sensing, and when E_b/ N₀ is bigger than 20 dB, given the required false alarm probability smaller than 15%, the difference of detection probability between the channel obtained using the proposed channel estimation algorithms and the ideal channel is less than 2.5%, respectively. Copyright © 2012 John Wiley & Sons, Ltd.

In amplify-and-forward-based cooperative spectrum sensing system, the influence of channel estimation error on system performance is firstly deduced, and then, two modified algorithms are proposed to improve the channel estimation performance for code division multiple access system and orthogonal frequency division multiplexing system, respectively. Simulation results verify the effectiveness of the two proposed channel estimation algorithms in cooperative spectrum sensing.

Narrow band interference (NBI) deteriorates the quality of the spectrum, leading to a poorer performance of modern universal mobile telecommunication system (UMTS) spread spectrum systems. The linear prediction algorithm is one of the most significant techniques to overcome NBI and enhance the performance of UMTS systems. In this paper, a modified linear prediction algorithm is proposed for NBI suppression in a conditionally stationary environment. This modification improves the error energy estimation in the auto-regression model of the linear prediction. The convergence of the proposed algorithm is evaluated, and its robustness is verified using Kullback–Leibler metrics for conditionally stationary NBI signals. Computer simulations are carried out, and the obtained results demonstrate the performance of the proposed algorithm and its compliance with UMTS protocols. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, a modified linear prediction algorithm is proposed for narrowband interference suppression in a conditionally stationary environment. This modification improves the error energy estimation in the auto-regression model of the linear prediction. The convergence of the proposed algorithm is evaluated, and its robustness is verified using Kullback-Leibler metrics for conditionally stationary narrowband interference signals.

The wavelet packets based multicarrier (MC) multicode (MCD) code-division multiple-access (CDMA) transceiver consists of the MCD part, which ensures the transmission for high speed and flexible data rate; the MC part contributing to robustness to frequency-selective fading and flexibility for handling multiple data rates; and wavelet packets (WPs) modulation technique, which contributes to the mitigation of the interference problems. As WPs have lower sidelobes compared with sinusoidal carriers, this system is very effective in reducing the problem of inter-carrier interference. Of course, like any CDMA system, the system can suppress a given amount of interference. This paper considers an interference suppression scheme which will enhance the performance of the system. The receiver employs suppression filters to mitigate the effect of narrow-band jammer interference. The framework for the system and the performance evaluation are presented in terms of the bit error rate and the outage probability over a Nakagami fading channel. Also, we investigate how the performance is influenced by various parameters, such as the number of taps of the suppression filter and the ratio of narrow-band interference bandwidth to the spread-spectrum bandwidth. Finally, the performance of the system is compared with the performance of sinusoidal based MC/MCD-CDMA system denoted Sin-MC/MCD-CDMA. Copyright © 2012 John Wiley & Sons, Ltd.

A novel wavelet packets based multicarrier multicode CDMA is proposed in this paper. As WPs have lower sidelobes compared with sinusoidal carriers, this system is very effective in reducing the inter-carrier interference. The receiver in this paper employs suppression filters to mitigate the effect of narrow-band jammer interference. The performance evaluation for the system is presented in terms of bit error rate and outage probability. Also, the performance of the system is compared with the performance of sinusoidal based MC/MCD-CDMA.

Gaussian and hyperbolic angle-of-arrival probability density functions are used to derive channel capacity of orthogonal frequency division multiplexing transmission employing diversity techniques and adaptive policies in cellular wireless fading environments. The intercarrier interference (ICI) power is quantified and given as a function of Doppler shift f_d, symbol duration T_s, frequency correction ζ and propagation ratio τ. Two scattering distributions, which have been shown to closely fit experimental empirical data, are examined in this paper: (i) Gaussian and (ii) hyperbolic. A new signal-to-interference-and-noise ratio probability density function is derived as a function of the ICI power using diversity techniques and adaptive policies. From that, effects of f_dT_s, ζ and τ on channel capacity can be discussed. The main contribution of this work is to model ICI as a function of f_d and symbol duration T_s. Two diversity techniques are considered: (i) maximal ratio combining and (ii) selective combining. Three adaptive policies are studied: (i) optimal rate adaptation, (ii) optimal rate and power adaptation and (iii) channel inversion with fixed rate. Closed-form expressions and bounds on various channel capacity with orthogonal frequency division multiplexing transmission under different scenarios are derived. Copyright © 2012 John Wiley & Sons, Ltd.

This paper studies channel capacity of orthogonal frequency division multiplexing systems using adaptive policies and linear diversities such as selection combining and maximal ratio combining. The effects of channel scatterers are also considered. Simulation results are given.

In this paper, we propose three adaptive blind algorithms for multiuser multicarrier code division multiple-access systems in multipath fading channels. The proposed adaptive blind receivers are based on the property of the discreteness of the input data symbol and are updated in every symbol interval. We also use the concept that the variance of the output signal approaches to the variance of the desired signal to get the cost function. The three proposed receiver structures are the traditional finite impulse response (FIR) structure, the despreading (DES) filter structure and the generalized sidelobe canceller (GSC) structure. The advantage of the FIR filter is that the length of the filter weights does not have to be the same length as the spreading code. For the DES filter, the combination of the adaptive weight and the despreading code has the simplest structure than the other two proposed receiver structures. The constrained GSC filter is superior to the other two proposed receiver structures in the environments dominated by multiple-access interference. By this constraint, the blind GSC filter can guarantee to converge to the desired solution. Simulation results are given to show the effectiveness and comparison of the proposed adaptive blind receivers.Copyright © 2012 John Wiley & Sons, Ltd.

Three adaptive blind algorithms are proposed in this paper. The advantage of the FIR filter is that the length of the filter weights does not have to be the same length as the spreading code. For the DES filter, the combination of the adaptive weight and the despreading code has the simplest structure than the other two proposed receiver structures. The constrained GSC filter is superior to the other two proposed receiver structures in the environments dominated by MAI.

Using directional antennas to reduce interference and improve throughput in multihop wireless networks has attracted much attention from the research community in recent years. In this paper, we consider the issue of minimum delay broadcast in multirate wireless mesh networks using directional antennas. We are given a set of mesh routers equipped with directional antennas, one of which is the gateway node and the source of the broadcast. Our objective is to minimize the total transmission delay for all the other nodes to receive a broadcast packet from the source, by determining the set of relay nodes and computing the number and orientations of beams formed by each relay node. We propose a heuristic solution with two steps. Firstly, we construct a broadcast routing tree by defining a new routing metric to select the relay nodes and compute the optimal antenna beams for each relay node. Then, we use a greedy method to make scheduling of concurrent transmissions without causing beam interference. Extensive simulations have demonstrated that our proposed method can reduce the broadcast delay significantly compared with the methods using omnidirectional antennas and single-rate transmission. In addition, the results also show that our method performs better than the method with fixed antenna beams. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we aim to minimize the total transmission delay for the gateway node to broadcast a packet to all the mesh routers in the case of multirate transmission and directional antennas. We first construct a broadcast tree by defining a new routing metric to select the relay nodes and compute the optimal antenna beams for each relay node. Then, we use a greedy method to make scheduling of concurrent transmissions without causing beam interference.

Although many researches on network mobility management have been carried out, a binding update storm, signaling overheads, and so on still exist in the past proposals. To avoid the binding update storm and to support route optimization as well as intra-domain data communication, a specifically designed solution with a distributed manner is proposed in this paper. By applying the derived analytical results, we demonstrate that the proposed solution is able to significantly outperform the closely related work in the literature.Copyright © 2012 John Wiley & Sons, Ltd.

To avoid the binding update storm and to support route optimization as well as intra-domain data communication, a specifically designed solution with a distributed manner is proposed in this paper. By applying the derived analytical results, we demonstrate that the proposed solution is able to significantly outperform the closely related work in the literature.

Spectrum sensing and access have been widely investigated in cognitive radio network for the secondary users to efficiently utilize and share the spectrum licensed by the primary user. We propose a cluster-based adaptive multispectrum sensing and access strategy, in which the secondary users seeking to access the channel can select a set of channels to sense and access with adaptive sensing time. Specifically, the spectrum sensing and access problem is formulated into an optimization problem, which maximizes the utility of the secondary users and ensures sufficient protection of the primary users and the transmitting secondary users from unacceptable interference. Moreover, we explicitly calculate the expected number of channels that are detected to be idle, or being occupied by the primary users, or being occupied by the transmitting secondary users. Spectrum sharing with the primary and transmitting secondary users is accomplished by adapting the transmission power to keep the interference to an acceptable level. Simulation results demonstrate the effectiveness of our proposed sensing and access strategy as well as its advantage over conventional sensing and access methods in terms of improving the achieved throughput and keeping the sensing overhead low.Copyright © 2012 John Wiley & Sons, Ltd.

We propose a cluster-based sensing and access scheme, in which synchronization and cooperation only happen among the secondary users who belong to the same cluster and adaptive sensing time scheme is used to reduce the sensing overhead. Furthermore, our method allows the secondary users to sense and access multiple channels. Spectrum sharing with primary users and secondary users is employed by adapting the transmission power to avoid causing harmful interference. To do this, the throughput is improved.

This paper addresses the problem of localization in sensor networks where, initially, a certain number of sensors are aware of their positions (either by using GPS or by being hand-placed) and are referred to as anchors. Our goal is to localize all sensors with high accuracy, while using a limited number of anchors. Sensors can be equipped with different technologies for signal and angle measurements. These measures can be altered by some errors because of the network environment that induces position inaccuracies. In this paper, we propose a family (AT-Family) of three new distributed localization techniques in wireless sensor networks: free-measurement (AT-Free) where sensors have no capability of measure, signal-measurement (AT-Dist) where sensors can calculate distances, and angle-measurement (AT-Angle) where sensors can calculate angles. These methods determine the position of each sensor while indicating the accuracy of its position. They have two important properties: first, a sensor node can deduce if its estimated position is close to its real position and contribute to the positioning of others nodes; second, a sensor can eliminate wrong information received about its position. This last property allows to manage measure errors that are the main drawback of measure-based methods such as AT-Dist and AT-Angle techniques. By varying the density and the error rate, simulations show that the three proposed techniques achieve good performances in term of high accuracy of localized nodes and less energy consuming while assuming presence of measure errors and considering low number of anchors. Copyright © 2012 John Wiley & Sons, Ltd.

We propose a family (AT-Family) of three new distributed localization techniques in wireless sensor networks: free-measurement (AT-Free) where sensors have no capability of measure, signal-measurement (AT-Dist) where sensors can calculate distances, and angle-measurement (AT-Angle) where sensors can calculate angles. These methods determine the position of each sensor while indicating the accuracy of its position. By varying the density and the error rate, simulations show that the three proposed techniques achieve high precisions for all localized nodes while consuming less energy, introducing errors on positions and considering low number of anchors.

In this paper, we analyze the performance of cognitive amplify-and-forward (AF) relay networks with beamforming under the peak interference power constraint of the primary user (PU). We focus on the scenario that beamforming is applied at the multi-antenna secondary transmitter and receiver. Also, the secondary relay network operates in channel state information-assisted AF mode, and the signals undergo independent Nakagami-m fading. In particular, closed-form expressions for the outage probability and symbol error rate (SER) of the considered network over Nakagami-m fading are presented. More importantly, asymptotic closed-form expressions for the outage probability and SER are derived. These tractable closed-form expressions for the network performance readily enable us to evaluate and examine the impact of network parameters on the system performance. Specifically, the impact of the number of antennas, the fading severity parameters, the channel mean powers, and the peak interference power is addressed. The asymptotic analysis manifests that the peak interference power constraint imposed on the secondary relay network has no effect on the diversity gain. However, the coding gain is affected by the fading parameters of the links from the primary receiver to the secondary relay network. Copyright © 2012 John Wiley & Sons, Ltd.

This paper studies optimal resource allocation for multiple two-way relay in orthogonal frequency division multiplexing systems. A joint optimization problem considering power allocation, relay selection, and subcarrier pairing to maximize the sum capacity under individual and total power constraints is solved in polynomial time by dual method. Simulation results demonstrate that the proposed optimal resource algorithm yields substantial performance improvement over baseline scheme and that the proposed suboptimal algorithms can achieve a trade-off between performance and complexity.

Recently, zero-forcing beamforming has been widely used for multiple-input and multiple-output broadcast channels, because it could provide suboptimal capacity with low complexity. To increase the sum data rate, a good user selection algorithm is attractive. In this paper, a new user selection algorithm named maximum product of effective channel gains is presented. The proposed algorithm is described mathematically, and the lower bound of the sum capacity is demonstrated to be proportional to the product of effective channel gains. Our simulation results show that maximum product of effective channel gains can achieve higher sum rate compared with the classical algorithm, semi-orthogonal user selection, with the same complexity order, especially when the signal-to-noise ratio is high; in addition, the complexity of the proposed algorithm is superior to minimum of the Frobenius norm of the pseudo-inverse algorithm. Meanwhile, the number of users that can be served simultaneously is equal to the number of transmission antennas, which is the maximum performance that can be achieved. Copyright © 2012 John Wiley & Sons, Ltd.

Zero-forcing beamforming is widely used for multiple-input and multiple-output broadcast channel, because it provides sub-optimal capacity with low complexity. To increase the sum data rate, a user selection algorithm named maximum product of effective channel gains, which achieves higher sum rate compared with the classical algorithm without increasing complexity, is presented.

In this paper, we propose a coexistence scheme that allows radio-frequency identification readers or sinks to collect data from radio-frequency identification tags or sensors that use IEEE 802.15.4 wireless personal area network standard and send it to the access point via an IEEE 802.11 wireless local area network. The proposed scheme uses time scheduling and bridging via readers to allow for simultaneous operation of heterogeneous wireless networks that operate in the industrial, scientific, and medical frequency band at 2.4 GHz. A simple sleep management approach is developed that allows tags to reduce their power consumption as well as collision rate. To provide timely reaction to sudden changes in tag population or reader availability, we devise a scheme where the scheduling parameters are adjustable and readers are mobile. We evaluate the performance of our solution in four scenarios and confirm the flexibility of the proposed approach.Copyright © 2012 John Wiley & Sons, Ltd.

We propose a coexistence scheme that allows radio-frequency identification readers or sinks to collect data from radiofrequency identification tags that use IEEE 802.15.4 wireless personal area network standard and send it to the access point via an IEEE 802.11 wireless local area network. A simple sleep management approach allows tags to reduce their power consumption as well as collision rate. To provide timely reaction to sudden changes in tag population or reader availability, we devise a scheme where the scheduling parameters are adjustable and readers are mobile.

This paper studies optimal resource allocation for multiple network-coded two-way relay in orthogonal frequency division multiplexing systems. All the two-way relay nodes adopt amplify-and-forward and operate with analog network coding protocol. A joint optimization problem considering power allocation, relay selection, and subcarrier pairing to maximize the sum capacity under individual power constraints at each transmitter or total network power constraint is first formulated. By applying dual method, we provide a unified optimization framework to solve this problem. With this framework, we further propose three low-complexity suboptimal algorithms. The complexity of the proposed optimal resource allocation (ORA) algorithm and three suboptimal algorithms are analyzed, and it is shown that the complexity of ORA is only a polynomial function of the number of subcarriers and relay nodes under both individual and total power constraints. Simulation results demonstrate that the proposed ORA scheme yields substantial performance improvement over a baseline scheme, and suboptimal algorithms can achieve a trade-off between performance and complexity. The results also indicate that with the same total network transmit power, the performance of ORA under total power constraint can outperform that under individual power constraints. Copyright © 2012 John Wiley & Sons, Ltd.

This paper studies optimal resource allocation for multiple two-way relay in orthogonal frequency division multiplexing systems. A joint optimization problem considering power allocation, relay selection, and subcarrier pairing to maximize the sum capacity under individual and total power constraints is solved in polynomial time by dual method. Simulation results demonstrate that the proposed optimal resource algorithm yields substantial performance improvement over baseline scheme and that the proposed suboptimal algorithms can achieve a trade-off between performance and complexity.

This paper presents a pipelined forwarding scheme with energy balance for hexagonal wireless sensor networks (H-WSN). An H-WSN consists of hexagonal clusters in which the distance between any two cluster heads is , where R is the radius of a hexagonal cluster. A trade-off exists in pipelined forwarding for an H-WSN; that is, reducing pipeline lengths can decrease data forwarding delay, but it will adversely increase the number of clusters, which consequently increases the total collecting time of a mobile sink. This paper therefore introduces a mobile sink data collecting and routing scheme to dynamically adjust the pipeline lengths and to periodically switch pipeline directions. With this mobile sink data collecting and routing, the overall system throughput is increased, and the energy consumptions among all cluster heads are balanced. Copyright © 2012 John Wiley & Sons, Ltd.

This paper presents a pipelined forwarding scheme with energy balance for hexagonal wireless sensor networks. A trade-off exists in pipelined forwarding for an H-WSN; that is, reducing pipeline lengths can decrease data forwarding delay, but it will adversely increase the total collecting time of a mobile sink. A mobile sink data collecting and routing scheme is therefore introduced to dynamically adjust the pipeline lengths and to periodically switch pipeline directions.

In this paper, we study the channel service process of a multiple-input multiple-output (MIMO) system over an independent and identically distributed (i.i.d.) fading channel. One key problem of communication over fading MIMO channels is what kind of service the MIMO channel can provide. In this paper, this problem is investigated in terms of channel service process. Assuming that the channel state information is available at the receiver, the channel service process S(t) is defined as the integral of the instantaneous channel capacity over a time interval of length t, which specifies the service provided by the channel during the period. Using the characteristic function approach and the infinitely divisible law, it is proved that the channel service process S(t) is a deterministic linear function of time t, other than any curve form or a stochastic process. Specifically, , where is a constant equal to the corresponding ergodic capacity. This result has two implications: (i) i.i.d. fading MIMO channels can support a constant rate traffic stream of rate without higher layer transmission delay; (ii) the ergodic capacity is the actual transmission capacity of the fading channel, other than only a statistical average value. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we study the channel service process of a multiple-input multiple-output (MIMO) system over an independent and identically distributed (i.i.d.) fading channel. One key problem of communication over fading MIMO channels is what kind of service the MIMO channel can provide. In this paper, this problem is investigated in terms of channel service process. Assuming that the channel state information is available at the receiver, the channel service process S(t) is defined as the integral of the instantaneous channel capacity over a time interval of length t, which specifies the service provided by the channel during the period. Using the characteristic function approach and the infinitely divisible law, it is proved that the channel service process S(t) is a deterministic linear function of time t, other than any curve form or a stochastic process. Specifically, , where is a constant equal to the corresponding ergodic capacity. This result has two implications: (i) i.i.d. fading MIMO channels can support a constant rate traffic stream of rate without higher layer transmission delay; (ii) the ergodic capacity is the actual transmission capacity of the fading channel, other than only a statistical average value.

Data communication technology is one of the key subsystems in communication-based train control (CBTC), which is an automated train control system for railways that ensures safe operation of rail vehicles using data communications. In CBTC systems, less service availability could cause train derailment, collision or even catastrophic loss of lives or assets. Therefore, the availability of data communication should be carefully considered in designing CBTC systems. In this paper, we propose two wireless local area network (WLAN)-based data communication systems with redundancy in CBTC systems. The availability is analyzed using continuous time Markov chain (CTMC) model. We also model the WLAN-based data communication system behavior with deterministic and stochastic Petri net (DSPN). The DSPN solution is used to show the soundness of our proposed CTMC model. Numerical examples illustrate that the proposed systems with redundancy can significantly improve service availability in CBTC systems. Copyright © 2012 John Wiley & Sons, Ltd.

Data communication technology is one of the key subsystems in communication-based train control (CBTC), which is an automated train control system for railways that ensures safe operation of rail vehicles using data communications. In this paper, we propose two wireless local area network (WLAN)-based data communication systems with redundancy in CBTC systems. The availability is analyzed using continuous time Markov chain (CTMC) model. We also model the WLAN-based data communication system behavior with deterministic and stochastic Petri net (DSPN). The DSPN solution is used to show the soundness of our proposed CTMC model.

Achieving high data quality and efficient network resource utilization is two major design objectives of wireless sensor networks (WSNs). However, these two objectives are often conflictive. By allowing sensors to report sampled data at high rates, fine-grained data quality can be obtained. However, the limited resources of a WSN make it difficult to support very high traffic rate. Therefore, the capability of adaptively adjusting sensor nodes' traffic-generating rates on the basis of the availability of network resources and application requirements is critical. This issue has attracted much attention recently, and some work has been carried out.

To achieve high data quality and improved utilization of network resources, in this paper, we propose rate-based adaptive precision setting (RAPS) protocol, which works in a way that each sensor can adaptively adjust its traffic-generating rate on the basis of the current network resources availability and application requirements. RAPS introduces the following two key factors into its design: application's precision requirement and packet arrival rate. Analytical and simulation results show that RAPS can achieve improved data quality while reducing packet delivery latency. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we propose a rate-based adaptive precision setting (RAPS) protocol. With RAPS used, each sensor node can adaptively adjust its traffic-generating rate on the basis of the current available network resources and application requirements. RAPS introduces the following two key features into its design: application's precision requirement and packet arrival rate. Analytical and simulation results show that RAPS can achieve improved data quality while reducing packet delivery latency.

In this paper, a weighted node selection technique in wireless sensor networks is proposed. It is an energy-efficient cooperative technique where a selected number of sensors at the transmitting end are connected with a selected number of sensors at the receiving end to form a virtual multi-input multi-output. The proposed technique is based on a weighted selection function that combines geographical location, inter-sensor distance in a cluster, channel estimate energy, power circuit, channel loss, mobility factor, and residual energy of each sensor. The weight of each of these parameters in the selection function depends on the degree that this parameter affects the energy consumption. Then, the cluster head selects the sensors with better selection parameters that reduce the overall energy consumption. The numerical results show that the proposed weighted node selection technique achieves a significant improvement in the energy consumption, delay, and network lifetime than the conventional techniques with and without the selected number of sensors. Its improvement reaches 15% in the energy consumption that leads to an increase in the network lifetime by four times the network lifetime of other techniques.Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, an energy-efficient cooperative technique based on virtual multiple-input multiple-output is proposed for a wireless sensor network. The proposed technique assigns a weighted selection function for each sensor that reflects the impact degree of geographical location, inter-sensor distance in a cluster, channel estimate energy, power circuit, channel loss, mobility factor, and residual energy on the energy consumption. Then, the cluster head selects the sensors with better selection parameters that reduce the overall energy consumption.

A novel iterative algorithm for the efficient computation of the intersection areas of an arbitrary number of circles is presented. The algorithm, on the basis of a trellis structure, hinges on two geometric results, which allow the existence check and the computation of the area of the intersection regions generated by more than three circles by simple algebraic manipulations of the intersection areas of a smaller number of circles. The presented algorithm is a powerful tool for the performance analysis of wireless networks and finds many applications, ranging from sensor to cellular networks. As an example of practical application, an insightful study of the uplink outage probability in a wireless network with cooperative access points as a function of the transmission power and access point density is presented. Copyright © 2012 John Wiley & Sons, Ltd.

We present an iterative algorithm to compute the intersection areas among an arbitrary number of circles. The algorithm is based on two geometric results, which highly simplifies the required computational effort. Applications to wireless communications are considered, and the algorithm is used to investigate the parameter setup in a cellular network when base station cooperation is employed.

In this paper, turbo equalization for transmission over doubly selective channels is proposed. The maximum a posteriori probability (MAP) algorithm is used for channel detection as well as for channel decoding. The detection/decoding constituents can exchange soft information in an iterative manner resulting in the so-called turbo equalization. The time-varying multi-path fading channel is modeled using the basis expansion model (BEM). In this BEM, the time-varying channel is viewed as a bank of time-invariant finite impulse response filters, and the time variation is captured by means of time-varying complex exponential basis functions. Therefore, the time-varying transition tables that characterize the time-varying channel can also follow a similar BEM. The complexity of the MAP channel detector is rather prohibitive for practical applications. This motivates the search for lower-complexity soft-output channel detectors. For this purpose, soft-output linear minimum-mean square error (LMMSE)-based channel detectors are proposed for single carrier as well as for multi-carrier systems. With the use of Gaussian approximation, expressions for the a posteriori and extrinsic log-likelihood ratios have been derived. The performance of the proposed turbo equalization schemes are evaluated using numerical simulations. Copyright © 2012 John Wiley & Sons, Ltd.

Turbo equalization for transmission over doubly selective channels is proposed. The optimum soft-output maximum a posteriori probability (MAP) equalizer is used for channel detection. The complexity of the MAP channel detector is rather prohibitive for practical applications, which motivates the search for suboptimum lower-complexity soft-output channel detectors. For this purpose, soft-output linear minimum-mean square error (LMMSE)-based channel detectors are proposed. With the use of Gaussian approximation, expressions for the a posteriori and extrinsic log-likelihood ratios are derived.

In this paper, we present the performance of selective combining decode-and-forward relay networks in independent and non-identically distributed Nakagami-n and Nakagami-q fading channels by using the best–worse and the decoding-set approaches. The outage probability, moment generation function, symbol error probability and average channel capacity are derived in closed-form using the signal to noise ratio (SNR) statistical characteristics. After that, we analyze the outage probability at high SNRs, and then, we optimize it. Beside the optimum method, we have proposed a sub-optimum adaptive method. Also, we derive the outage probability for the selection-combining case with the direct link between the source and the destination. Finally, for comparison with analytical formulas, we perform some Monte-Carlo simulations. Copyright © 2012 John Wiley & Sons, Ltd.

The performance of selective combining decode-and-forward relay networks in independent and non-identically distributed Nakagami-n and Nakagami-q fading channels is analyzed. The outage probability, moment generation function, symbol error probability, and average channel capacity are derived in closed-form using the signal to noise ratio (SNR) statistical characteristics. Subsequently, we analyze the outage probability at high SNRs, and then, we optimize it, analytically. The simulation results verify the accuracy and the correctness of the proposed analysis.

To be compatible with the legacy 802.11, there are two major medium access control (MAC) behaviors, high throughput (HT) and non-high throughput (non-HT), in the 802.11n. In this paper, we analyze and compare the energy efficiencies of different MAC behaviors in 802.11n on the basis of the Bianchi model and our previous works to evaluate the performance of the different MAC behaviors regarding HT and non-HT. Our studies try to provide the decision for the mobile stations to enable the HT of 802.11n or not based on the consideration of energy efficiency. Studies show that owing to the large power consumption in HT, it is not suitable for limited power devices to carry WWW traffics by multiple-input multiple-output transmission because of large overheads of physical layer in the HT mode. However, if large file transmissions by File Transfer Protocol are considered, the energy efficiency in HT MAC can be very high because of the large aggregated frame size. It is especially true when the number of active stations is large because of the decrease in idle listening time by using the techniques applied in HT MAC such as Aggregate MAC Protocol Data Unit and Block-ACK. These characteristics in the HT mode can overwhelm the larger overheads of physical layer compared with that in the non-HT mode when large files are needed to be uploaded. Copyright © 2012 John Wiley & Sons, Ltd.

It is not suitable for small mobile devices such as smart phones and personal digital assistant to enable the high throughput mode of 802.11n to transmit the legacy traffics such as WWW for browsing the common Web pages without the embedded large image. However, if the transmitted traffics are large files such as HDTV video or File Transfer Protocol files, the energy efficiency is much higher than those in non-high throughput, and it has much higher medium access control efficiency and throughput owing to shorter transmission time.

In this study, a deterministic deployment problem in wireless sensor networks is examined. On the basis of information coverage, we study equilateral triangle and square deployment strategies, and we provide the maximum distance between sensors in order to reach the required detection probability for any point in the monitoring field. First, we provide a model of the signal attenuation. On the basis of the detected signal from the K sensors, the best linear and unbiased estimation is used to estimate the signal parameter with the corresponding error. For the equilateral triangle deployment, the maximum distance between sensors is computed and provided when the received signal data from two or three sensors is used. Similarly, we have computed and supplied the maximum distance between sensors in the square deployment. Simulations are performed to show the relationship between the number of sensors and the detection probability. The simulation results show that it is not a good choice to improve the detection probability with a larger number of sensors.Copyright © 2012 John Wiley & Sons, Ltd.

We study equilateral triangle and square deployment strategies, and we provide the maximum distance between sensors in order to reach the required detection probability for any point in the monitoring field. Simulations are performed to show the relationship between the number of sensors and the detection probability.

Vehicular ad hoc networks are emerging as a promising approach to improve traffic safety and provide a wide range of wireless applications to drivers and passengers on the road. In order to perform reliable and trusted vehicular communications, one requirement is to ensure peer vehicle credibility by means of validating digital certificate attached to messages that are transmitted by other vehicles. However, in vehicular communication systems, certificate validation is more time consuming than in traditional networks because each vehicle receives a large number of messages in a short period. Another concern is the unsuccessful delivery of information between vehicles and other entities on the road due to their high mobility rate. For these reasons, we seek new solutions that will aid in speeding up the process of certificate validation. In this article, we propose a certificate revocation status validation scheme using the concept of clustering from data mining that can meet the aforementioned requirements. We employ the technique of k-Means clustering to boost the efficiency of certificate validation, thereby enhancing the security of a vehicular ad hoc network. Additionally, a comprehensive security analysis for this scheme is presented; the analysis shows that this scheme can effectively improve the validation of certificates and thus increase the communication security in vehicular ad hoc networks. Copyright © 2012 John Wiley & Sons, Ltd.

We propose a certificate revocation status validation scheme using the concept of clustering from data mining. We suggested the addition of two new attributes as an extension to the existing structure of the X.509 certificate standard.

A base station is the controller and the data-receiving center of a wireless sensor network. Hence, a reliable and secure base station is critical to the network. Once an attacker locates the base station, he or she can do many damages to the network. In this paper, we examine the base station location privacy problem from both the attack and defense sides. First, we present a new attack on base station: parent-based attack scheme (PAS). PAS can locate a base station within one radio (wireless transmission) range of sensors in high-density sensor networks. Different from existing methods, PAS determines the base station location on the basis of parent–child relationship of sensor nodes. Existing base station protection schemes cannot defend against PAS. Second, on the basis of PAS, we propose a two-phase parent-based attack scheme (TP-PAS). Our simulation results demonstrate that TP-PAS is able to determine the base station successfully in both low-density and high-density sensor networks. Then, to defend against PAS and TP-PAS, we design a child-based routing protocol and a parent-free routing protocol for sensor networks. Our theory analysis and experiment results show that the parent-free routing protocol has more communication cost and less end-to-end latency compared with the child-based routing protocol. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we study the base station location privacy problem from both the attack and defense sides. First, we discuss novel attacks on base stations. These attacks determine the base station location based on parent-child relationship of sensor nodes. Existing base station protection schemes cannot defend these attacks. To defend against the attacks, we design two new secure routing protocols for sensor networks, and we validated both protocols by theoretical analysis and experiments.

For amplify-and-forward relay networks, we propose an iterative scheme to estimate channel and detect information symbols for the multi-antenna destination in spatially correlated noise. The equivalent channel coefficients and noise covariance are estimated by expectation–maximization algorithm. In addition, we discuss the initialization of iteration and analyze the modified Cramér–Rao bound to show the performance of the proposed iterative estimation. Moreover, on the basis of the structure of the proposed iterative estimator, a joint channel estimation and detection receiver is also provided. Finally, simulation results show that the proposed channel estimator and receiver can achieve the optimal performances in amplify-and-forward relay networks with unknown noise correlation. Copyright © 2012 John Wiley & Sons, Ltd.

For amplify-and-forward relay networks, we propose an iterative scheme to estimate channel and detect information symbols for the multi-antenna destination in spatially correlated noise. The equivalent channel coefficients and noise covariance are estimated by expectation-maximization algorithm. Moreover, a joint channel estimation and detection receiver is also provided.

Global Navigation Satellite Systems positioning accuracy indoor and urban canyons environments are greatly affected by multipath because of distortions in its autocorrelation function. In this paper, we propose a new multipath mitigation technique based on the concept of S-curve shaping for the new alternative binary offset carrier (AltBOC)-modulated signals, which will most likely be used in both European Galileo system and Chinese Compass system. The definition of an optimum S-curve is employed to reduce the false lock points and to improve the multipath mitigation capability via determining the shape of the local code tracking reference function. The structure of the proposed code tracking loop for AltBOC signals is quite simple and only requires one complex correlator. Results demonstrate that the proposed technique provides superior multipath mitigation performance compared with the conventional receiver correlation techniques and removes the ambiguity completely. Copyright © 2012 John Wiley & Sons, Ltd.

We propose a new multipath mitigation technique based on the concept of S-curve shaping for the new alternative binary offset carrier modulated signals, which will most likely be used in both European Galileo system and Chinese Compass system. The definition of an optimum S-curve is employed to reduce the false lock points and to improve the multipath mitigation capability via determining the shape of the local code tracking reference function.

Before the development of a large-scale wireless sensor network (WSN) infrastructure, it is necessary to create a model to evaluate the lifespan of the infrastructure, the system performance and the cost so that the best design solution can be obtained. Energy consumption is an important factor that influences the lifespan of WSNs. One of the ways to extend the lifespan of WSNs is to design wireless sensor nodes with low power consumption. This involves component selection and the optimisation of hardware architecture, monitoring software system and protocols to satisfy the requirements of the particular applications. This paper proposes a comprehensive model to describe the workflow of a wireless sensor node. Parameter setup and energy consumption calculation are demonstrated through the model simulation. It provides a mathematical approach to dynamically evaluate the energy consumption of a sensor node. This will benefit the development of wireless sensor nodes based on microprocessors with limited computational capability. Therefore, the model can be applied in dynamic power management systems for wireless sensor nodes or in wireless communication protocols with energy awareness, in particular, for WSNs with self-organisation. More importantly, the generalisation of the model may be employed as a standard paradigm for the development of wireless sensor node with energy awareness. Copyright © 2012 John Wiley & Sons, Ltd.

This paper proposes a comprehensive model to describe the workflow of a wireless sensor node. It provides a mathematical approach to dynamically evaluate the energy consumption of a sensor node. This will benefit the development of wireless sensor nodes based on microprocessors with limited computing capability. The model can be applied in dynamic power management systems for wireless sensor nodes and in self-organisation communication protocol with energy constraint and can be employed as a standard paradigm for development of wireless sensor node with energy awareness.

In order to provide more accurate detection of the primary user's activity in cognitive radio (CR) systems, cooperative spectrum sensing is proposed. The transmit diversity can also be employed by cooperative spectrum sensing to improve the performance of decision reporting. Hence, in the reporting channels between the cognitive users and the base station (BS), space time block code (STBC) scheme is considered in each cluster with time division multiple access (TMDA) method. In this paper, to improve the time efficiency in the case that one cluster makes sensing report, whereas the others do nothing but wait for their orders, we set each cluster with different sensing durations and the clusters will not stop the spectrum sensing until their results are reported. Furthermore, we also adopt the flexible sensing durations to decrease unnecessary energy consumption based on the clusters’ sensing sensitivities. Simulation results and analysis show the better detection performance and time efficiency of the proposed scheme.Copyright © 2012 John Wiley & Sons, Ltd.

We propose the scheme that each cluster with different sensing durations and the clusters will not stop the sensing until their results are reported to improve the time efficiency in the case that one cluster makes sensing report, whereas the others do nothing but wait for their orders in conventional spectrum sensing schemes. We also adopt the flexible sensing durations to decrease unnecessary energy consumption based on the clusters' sensing sensitivities. Simulation results and analysis show the efficiency of the proposed scheme.

With careful calculation of signal forwarding weights, relay nodes can be used to work collaboratively to enhance downlink transmission performance by forming a virtual multiple-input multiple-output beamforming system. Although collaborative relay beamforming schemes for single user have been widely investigated for cellular systems in previous literatures, there are few studies on the relay beamforming for multiusers. In this paper, we study the collaborative downlink signal transmission with multiple amplify-and-forward relay nodes for multiusers in cellular systems. We propose two new algorithms to determine the beamforming weights with the same objective of minimizing power consumption of the relay nodes. In the first algorithm, we aim to guarantee the received signal-to-noise ratio at multiusers for the relay beamforming with orthogonal channels. We prove that the solution obtained by a semidefinite relaxation technology is optimal. In the second algorithm, we propose an iterative algorithm that jointly selects the base station antennas and optimizes the relay beamforming weights to reach the target signal-to-interference-and-noise ratio at multiusers with nonorthogonal channels. Numerical results validate our theoretical analysis and demonstrate that the proposed optimal schemes can effectively reduce the relay power consumption compared with several other beamforming approaches. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we study the collaborative downlink signal transmission with multiple amplify-and-forward relay nodes for multiusers in cellular systems. We propose two new algorithms to determine the beamforming weights with the same objective of minimizing power consumption of the relay nodes. Numerical results validate our theoretical analysis and demonstrate that the proposed optimal schemes can effectively reduce the relay power consumption compared with several other beamforming approaches.

To improve the robustness and reliability of wireless transmissions, two complementary link adaptation techniques are employed: adaptive modulation and coding (AMC) at the physical layer and hybrid automatic retransmission request (HARQ) at the medium access control layer. Because of their effectiveness in combating errors induced by the wireless channel, AMC and HARQ are now integral components of most emerging broadband wireless system standards, for example, LTE and WiMAX. Spectral efficiency (SE) as measured in bit per second per Hertz is one important parameter used to characterize a wireless system for comparison between different systems or between different configurations of the same system. This work provides a holistic approach of cross-layer optimizations with the intent of maximizing SE by combining AMC and HARQ. It formulates closed-form equations for calculating the average SE for wireless systems with the Rayleigh fading channel model. A new online algorithm is developed to optimize SE for both Rayleigh and non-Rayleigh fading channel. Simulations using proven LTE model are performed to compare SE obtained from closed-form equations and the developed algorithm for different system configurations. With the developed algorithm to determine how many retransmissions required in addition to the initial transmission in advance depending on the current wireless channel condition, the latency can be reduced up to 24 ms when sending the initial transmission and all of its retransmissions sooner than waiting for retransmission requests as is done previously.Copyright © 2012 John Wiley & Sons, Ltd.

By determining how many retransmissions required in addition to the initial transmission in advance depending on the current wireless channel condition, the latency can be reduced up to 24 ms when sending the initial transmission and all of its retransmissions sooner than waiting for retransmission requests.

This paper considers channel quality indicator (CQI) reporting for data exchange in a two-way multi-relay network. We first propose an efficient CQI reporting scheme based on network coding, where two terminals are allowed to simultaneously estimate the CQI of the distant terminal-relay link without suffering from additional overhead. In addition, the transmission time for CQI feedback at the relays is reduced by half while the increase in complexity and the loss of performance are negligible. This results in a system throughput improvement of 16.7% with our proposed CQI reporting. Upper and lower bounds of the mean square error (MSE) of the estimated CQI are derived to study performance behaviour of our proposed scheme. It is found that the MSE of the estimated CQI increases proportionally with the square of the cardinality of CQI level sets although an increased number of CQI levels would eventually lead to a higher data rate transmission. On the basis of the derived bounds, a low-complexity relay selection (RS) scheme is then proposed. Simulation results show that, in comparison with optimal methods, our suboptimal bound-based RS scheme achieves satisfactory performance while reducing the complexity at least three times in case of large number of relays. Copyright © 2012 John Wiley & Sons, Ltd.

An efficient channel quality indicator (CQI) reporting scheme is proposed to reduce the transmission time for CQI feedback by half, whereas the increase in complexity and the loss of performance are negligible. Upper and lower bounds of the mean square error of the estimated CQI are derived to study performance behaviour of our proposed scheme, and a low-complexity relay selection scheme is proposed on the basis of the derived bounds.

Water-filled eigenchannels offer the highest multi-input multi-output (MIMO) information-theoretic capacity, but digital techniques such as quadrature amplitude modulation and finite block lengths will degrade the capacity from the Shannon limit to the capacity of a digital link. Furthermore, eigen-MIMO requires channel overheads, such as estimating the channel state information (CSI) and feeding it back to the transmitter, which further compromise the capacity. In this paper, the joint influence of channel estimation and imperfect feedback on the information-theoretic capacity and the practicable capacity is analyzed. The channel is modeled as static over a MIMO channel block. In each block, the forward channel is used for CSI estimation and for the payload data transmission. In the back direction, the channel is used to feed back a quantized form of the CSI to the transmitter with a throughput constraint. These three channel usages are combined into an effective simplex channel simplifying the capacity analysis. The capacities are formulated as functions of the link parameters, enabling optimization of the number of training symbols, the feedback duration, and the power allocation for training and data transfer, with the criterion of maximum capacity. The results presented are subject to the usual approximations used in communications theory. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, the eigen-MIMO capacity is maximized in the presence of different practical impairments such as channel estimation, imperfect feedback, and digital modulation. The capacity is formulated as a function of the link parameters, enabling optimization of the number of training symbols, the feedback duration, and the power allocation for training and data transfer, with the criterion of maximum capacity.

Cognitive radio (CR) is a promising technique for future wireless networks, which significantly improves spectrum utilization. In CR networks, when the primary users (PUs) appear, the secondary users (SUs) have to switch to other available channels to avoid the interference to PUs. However, in the multi-SU scenario, it is still a challenging problem to make an optimal decision on spectrum handover because of the the accumulated interference constraint of PUs and SUs. In this paper, we propose an interference-aware spectrum handover scheme that aims to maximize the CR network capacity and minimize the spectrum handover overhead by coordinating SUs’ handover decision optimally in the PU–SU coexisted CR networks. On the basis of the interference temperature model, the spectrum handover problem is formulated as a constrained optimization problem, which is in general a non-deterministic polynomial-time hard problem. To address the problem in a feasible way, we design a heuristic algorithm by using the technique of Branch and Bound. Finally, we combine our spectrum handover scheme with power control and give a convenient solution in a single-SU scenario. Experimental results show that our algorithm can improve the network performance efficiently.Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we propose an interference-aware spectrum handover scheme that aims to maximize the cognitive radio network capacity by coordinating SUs’ handover decision optimally in the PU–SU coexisted cognitive radio networks. On the basis of the interference temperature model, the spectrum handover problem is formulated as a constrained optimization problem that can be solved by the technique of Branch and Bound. Finally, we combine our spectrum handover scheme with power control and give a convenient solution in a single-SU scenario.

In this work, we develop a prioritized bridging mechanism between the IEEE 802.15.6-based wireless body area networks (WBANs) and the IEEE 802.11e enhanced distributed channel access (EDCA)-based wireless local area network (WLAN) to convey the medical data to the medical center. We map the eight WBAN user priorities (UPs) into the four WLAN access categories (ACs) to provide the required quality of service and prioritization for the health variables generated by the WBAN nodes. By assignment of WBAN UPs with default medium access control parameters to eight different medical data streams and under the presence of ordinary nodes, we investigate the impact of WLAN AC differentiation by arbitrary inter-frame space (AIFS) and contention window (CW) on performance of medical and regular nodes’ data streams. The results of this work indicate that the AC differentiation by AIFS outperforms the differentiation by CW in the sense that it does not deteriorate the end-to-end delay of relayed WBAN traffic and ordinary WLAN traffic.Copyright © 2012 John Wiley & Sons, Ltd.

In this work, we develop a prioritized bridging mechanism between the IEEE 802.15.6-based wireless body area networks (WBANs) and the IEEE 802.11e enhanced distributed channel access-based wireless local area network (WLAN) to convey the medical data to the medical center. The results of this work indicate that the access category differentiation by arbitrary inter-frame space outperforms the differentiation by contention window in the sense that it does not deteriorate the end-to-end delay of relayed WBAN traffic and ordinary WLAN traffic.

Sensing coverage is one of fundamental problems in wireless sensor networks. In this paper, we investigate the polytype target coverage problem in heterogeneous wireless sensor networks where each sensor is equipped with multiple sensing units and each type of sensing unit can sense an attribute of multiple targets. How to schedule multiple sensing units of a sensor to cover multiple targets becomes a new challenging problem. This problem is formulated as an integer linear programming problem for maximizing the network lifetime. We propose a novel energy-efficient target coverage algorithm to solve this problem based on clustering architecture. Being aware of the coverage capability and residual energy of sensor nodes, the clusterhead node in each cluster schedules the appropriate sensing units of sensor nodes that are in the active status to cover multiple targets in an optimal way. Extensive simulations have been carried out to validate the effectiveness of the proposed scheme. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we investigate the polytype target coverage problem in heterogeneous wireless sensor networks where each sensor is equipped with multiple sensing units and each type of sensing unit can sense an attribute of multiple targets. This problem is formulated as an integer linear programming problem for maximizing the network lifetime. We propose a novel energy-efficient target coverage algorithm to schedule suitable nodes to cover multiple targets in an optimal way based on clustering architecture.

In cooperative wireless networks, relay nodes are employed to improve the performance of the network in terms of throughput and reliability. However, the presence of malicious relay nodes in the network may severely degrade the performance of the system. When a relay node behaves maliciously, there exists a possibility that such a node refuses to cooperate when it is selected for cooperation or deliberately drops the received packets. Trust establishment is a mechanism to detect misbehaving nodes in a network. In this paper, we propose a trust establishment method for cooperative wireless networks by using Bayesian framework. In contrast with the previous schemes proposed in wireless networks, this approach takes the channel state information and the relay selection decisions into account to derive a pure trust value for each relay node. The proposed method can be applied to any cooperative system with a general relay selection policy whose decisions in each cooperative transmission are independent of the previous ones. Moreover, it does not impose additional communication overhead on the system as it uses the available information in relay selection procedure. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we propose a trust establishment scheme for cooperative wireless networks by using Bayesian framework. In contrast with the previous schemes proposed in wireless networks, this approach takes the channel state information and the relay selection decisions into account to derive a pure trust value for each relay node. By using simulations, we demonstrated the effectiveness of the proposed scheme.

Collaborative communication produces high power gain and significantly reduces bit error rate (BER) if both frequency and phase synchronization are achieved. In this paper, a novel collaborative communication system with imperfect phase and frequency synchronization that includes the influence of noise and fading is proposed, modeled, theoretically analyzed, and simulated. Mathematical expressions are derived for the received power as a function of number of collaborative nodes and BER as a function of signal to noise ratio (E_b ∕ N₀). To analyze the energy efficiency of our proposed collaborative communication system, energy consumption of the system is modeled, simulated, and analyzed by considering the parameters of the off-the-shelf products. Analytical and simulation results showed that the proposed system produces significant power gain and reduction in BER in the presence of phase errors, frequency errors, additive white Gaussian noise, and Rayleigh fading. A detailed theoretical analysis and Monte Carlo simulation revealed that the proposed collaborative communication system is an energy efficient communication system that can be implemented in sensor networks, as approximately N (number of collaborative nodes) times less total transmitted power is required than for the single input single output communication for a specifies transmission range. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, a novel collaborative communication system with imperfect phase and frequency synchronization that includes the influence of noise and fading is proposed, modelled, theoretically analyzed, and simulated. To analyze the energy efficiency of our proposed collaborative communication system, energy consumption of the system is modelled, simulated, and analyzed by considering the parameters of the off-the-shelf products. A detailed theoretical analysis and Monte Carlo simulation revealed that the proposed system produces significant power gain and reduction in bit error rate.

In this paper, we address the energy-efficient connectivity problem of a wireless sensor network (WSN) that consists of (1) static sensor nodes that have a short communication range and limited energy level, and (2) relay nodes that have a long communication range and unlimited power supply, and that can be added or relocated arbitrarily. For such a WSN, existing studies have been focused on the design of efficient approximation algorithms to minimize the number of relay nodes. By contrast, we propose a unified backbone construction framework that can be performed in a centralized manner with two objectives: (1) to minimize the number of nodes in the backbone and (2) to maximize the lifetime of the network. To solve such a challenging problem, we formulate three subproblems: (1) partial dominating set with energy threshold (PDSET); (2) partial dominating set with largest residual energy (PDSLE); and (3) minimum relay node placement (MRNP). For these three subproblems, we develop polynomial-time algorithms. We also prove that our algorithm for PDSLE is optimal, and our algorithm for the PDSET and MRNP problems have small approximation ratios. Numerical results show that the proposed framework can significantly improve energy efficiency and reduce backbone size. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we address the energy-efficient connectivity problem of wireless sensor network that consists of (1) static sensor nodes that have a short communication range and limited energy level and (2) relay nodes that have a long communication range and unlimited power supply, which are used to connect the static sensor nodes. For relay node placement problem, we prove that a well-known existing scheme, that is, the steinerized minimum spanning tree algorithm, has an approximation ratio of 6, and a 3-star searching based algorithm has an approximation ratio of 5.

In this work, we introduce a priority-aware deterministic access protocol called Vehicular Deterministic Access (VDA). VDA is based on 802.11p/DSRC and allows vehicles to access the shared medium in collision-free periods. Particularly, VDA supports two types of safety services (emergency and routine safety messages) with different priorities and strict requirements on delay. To avoid long delays and high packet collisions, VDA allows vehicles to access the wireless medium at selected times with a lower contention than would otherwise be possible within a two-hop neighborhood by the classical 802.11p Enhanced Distributed Channel Access or Distributed Coordination Function schemes. A non-VDA-enabled vehicle, that is, a vehicle not configured with the optional VDA capability over 802.11p, may start transmitting on the shared channel just before or during the VDA opportunities reserved for vehicles with VDA capabilities. To avoid the aforementioned issues and prevent interfering transmissions from VDA-enabled vehicles and non-VDA-enabled vehicles, we also proposed a novel scheme called extended VDA. We analyzed the impact of several design tradeoffs between the contention free period/contention period dwell time ratios on the performance of safety applications with different priorities for VDA and extended VDA. Simulations show that the proposed schemes clearly outperform the backoff-based schemes currently used by 802.11p in high communication density conditions while bounding the transmission delay of safety messages and increasing the packet reception rate. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we show how we minimize contention between high-priority safety-oriented routine or emergency traffic and non-safety application traffic using a deterministic access method over 802.11p called Vehicular Deterministic Access (VDA). VDA provides bounded delays and low losses particularly for emergency messages. We investigated a mechanism called extended VDA that prevents interfering 802.11p/DCF vehicles, with deterministic access enabled, from accessing the scheduled transmission opportunities during the reserved time slots for vehicles using deterministic VDA access over 802.11p/DSRC.

This paper introduces admission control policies for WiMAX networks, which aim to reach three main goals: restrict the number of simultaneous connections in the system so that the resources available for the uplink scheduler are sufficient to guarantee the quality-of-service requirements for each connection, support the service provider expectations by maximizing the revenue, and maximize user satisfaction by granting additional resources. The optimal solution to meet these goals is non-deterministic polynomial-time hard and therefore cannot be solved in acceptable polynomial time. For this reason, both optimal and polynomial time heuristic solutions are introduced. Simulation experiments are used to evaluate and compare the proposed policies. Copyright © 2012 John Wiley & Sons, Ltd.

This paper introduces admission control policies for WiMAX networks. The proposed policies restrict the number of simultaneous uplink connections in the system so that resources available to the uplink scheduler are sufficient to guarantee the quality-of-service requirements of the connections. Moreover, these policies support the service provider and the users expectations by maximizing the network revenue as well as the network utility.

In this paper, we investigate the deficiency of uncontrolled asymmetrical transmission power over multiple channels in ad hoc environments. We further propose a novel distributed transmission power control protocol called the distributed power level (DPL) protocol for multi-channel ad hoc networks without requiring clock synchronization. Specifically, different transmission power levels are assigned to different channels, and nodes search for an idle channel on the basis of the received power so that the maximum allowable power of the preferred data channel is larger than or equal to the received power. If the most preferred channel of the least maximum power is busy, the nodes are able to select the next channel and so forth. As a result, interference is reduced over channels because the nodes that require higher transmission power are separated from interfering with the nodes that require lower transmission power. Two transmission power control modes are introduced for DPL: symmetrical and asymmetrical. For the symmetrical DPL protocol (mode), nodes transmit at the same power level assigned to the selected channel. On the other hand, for the asymmetrical DPL protocol, nodes are allowed to transmit at a lower or equal power level that is assigned to the selected channel. Extensive ns-2-based simulation results are presented to demonstrate that the proposed protocols can enhance the network throughput compared with the existing uncontrolled asymmetrical transmission power protocol.Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we propose a novel distributed transmission power control protocol called the distributed power level (DPL) protocol for multi-channel ad hoc networks, and the DPL protocol allocates different maximum allowable power values to different channels. A node selects a channel if the minimum required power is equal to or greater than the maximum allowable power level of the channel. In addition, two transmission power control modes are introduced for the DPL protocol: symmetrical and asymmetrical.

Common Radio Resource Management techniques have shown great promise in both enhancing network operation and user satisfication. Such gains are achieved through the joint management of the individual access technologies in a Heterogeneous Wireless Network. The objective of this work is to expand on the existing body of work to accommodate heterogeneity not just at the traditional access-network level but to other connectivity modes such as dynamic spectrum access. Such modes affect operator profitability in both the long and short terms. Specifically, we explore the design of a cost-management model that adapts to the short-term variability in connectivity costs. We also display the operational aspects and effectiveness of this functionality through both simulation and an analytical model. Copyright © 2012 John Wiley & Sons, Ltd.

The objective of this work is to expand on the existing body of work in Common Radio Resource Management to accommodate heterogeneity not just at the traditional access-network level but also to other connectivity modes such as dynamic spectrum access. Such modes affect operator profitability in both the long and short terms. Specifically, we explore the design of a cost-management model that adapts to the short-term variability in connectivity costs. We also display the operational aspects and effectiveness of this functionality.

The IEEE 802.16 mesh network is a promising next generation wireless backbone network. In the network, the allocation of minislots is handled by centralized scheduling and distributed scheduling, which are independently exercised. However, the standard does not specify how the frame can be partitioned among its centralized and distributed schedulers. Through efficient partitioning that dynamically adapts the partitioning based on demand, network can support more user applications. Although a dynamic frame partitioning scheme to use Markov model has been studied, the dynamic frame partitioning method has not been fully investigated. This paper proposes two novel and general dynamic frame partitioning scheme for IEEE 802.16 mesh networks so that the minislot allocation can be more flexible and the utilization is increased. The two schemes respectively use GM(1,1)-Markov model and Grey–Verhulst–Markov model to predict efficient partitions for future frames according to the minislot utilization in current frames. Our study indicates that the two proposed schemes outperform the scheme of using Markov model. Copyright © 2012 John Wiley & Sons, Ltd.

This paper proposes two novel and general dynamic frame partitioning scheme for IEEE 802.16 mesh networks so that the minislot allocation can be more flexible and the utilization is increased. The two schemes, respectively, use GM(1,1)-Markov model and Grey-Verhulst-Markov model to predict efficient partitions for future frames according to the minislot utilization in current frames. Our study indicates that the two proposed schemes outperform the scheme of using Markov model.

This paper presents a bandwidth negotiation scheduling (BNS) for IEEE 802.16j mobile multihop relay (MMR) networks. In MMR networks, two bandwidth scheduling zones, Access and Relay zones, are specified for direct access and forwarding sessions, respectively. One of the novelties in the proposed BNS is that bandwidth negotiation is conducted between the Access and Relay zones. In other words, a higher-priority traffic class in a high-utilization zone may receive extra bandwidth from low-utilization zone when its delay constraint or bandwidth requirement cannot be satisfied. In addition, when the assigned bandwidth to non-real-time polling service (nrtPS) has exceeded its minimum requirement, the proposed BNS can avoid possible starvations for best effort (BE) traffic by receiving extra bandwidth from nrtPS. Through multidimensional Markov formulation, we evaluate the performance of the BNS and compare it with a fixed-boundary scheme. The analytical results have shown that the proposed BNS can increase delay-constraint satisfactions for real-time polling service and decrease the packet loss rate for BE. Furthermore, the overall system throughput can be increased significantly because of an improvement on bandwidth utilization. Copyright © 2012 John Wiley & Sons, Ltd.

With bandwidth negotiation scheduling (BNS), four different traffic classes from mobile stations and relay stations (RSs) are aggregated and scheduled, respectively, into the Access zone and Relay zone of an uplink frame. The proposed BNS at the base station or each RS consists of two stages, per-class scheduling and zone-negotiation scheduling. One of the novelties in the proposed BNS is that bandwidth negotiation is conducted between the Access and Relay zones.

Wireless sensor networks (WSNs) have significant potential in many application domains, ranging from precision agriculture and animal welfare to home and office automation. Although sensor network deployments have only begun to appear, the industry still awaits the maturing of this technology to realize its full benefits. The main constraints to large-scale commercial adoption of WSN have been the lack of available network management and control tools, such as for determining the degree of data aggregation prior to transforming it into useful information, localizing the sensors accurately so that timely emergency actions can be taken at an exact location, routing data by reducing sensor energy consumption, and scheduling data packets so that data are sent according to their priority and fairness. Moreover, to the best of our knowledge, no integrated network management solution comprising efficient localization, data scheduling, routing, and data aggregation approaches exists in the literature for a large-scale WSN. Thus, we introduce an integrated network management framework comprising sensor localization, routing, data scheduling, and data aggregation for a large-scale WSN. Experimental results show that the proposed framework outperforms an existing approach that comprises only localization and routing protocols in terms of localization energy consumption, localization error, end-to-end delay, packet loss ratio, and network energy consumption. Moreover, the proposed WSN management framework has potential in building a future “Internet of Things”. Copyright © 2012 John Wiley & Sons, Ltd.

To the best of our knowledge, large-scale wireless sensor networks still lack efficient network management components such as sensor localization, routing, data scheduling, and data aggregation approaches in a single framework. Thus, we introduce an integrated wireless sensor network management framework comprising all these network management components, which increases location accuracy, reduces sensor energy consumption, and schedules data packet to transmit them according to their priority and fairness, as well as reduces end-to-end data transmission delay.

The smart grid is an innovative energy network that will improve the conventional electrical grid network to be more reliable, cooperative, responsive, and economical. Within the context of the new capabilities, advanced data sensing, communication, and networking technology will play a significant role in shaping the future of the smart grid. The smart grid will require a flexible and efficient framework to ensure the collection of timely and accurate information from various locations in power grid to provide continuous and reliable operation. This article presents a tutorial on the sensor data collection, communications, and networking issues for the smart grid. First, the applications of data sensing in the smart grid are reviewed. Then, the requirements for data sensing and collection, the corresponding sensors and actuators, and the communication and networking architecture are discussed. The communication technologies and the data communication network architecture and protocols for the smart grid are described. Next, different emerging techniques for data sensing, communications, and sensor data networking are reviewed. The issues related to security of data sensing and communications in the smart grid are then discussed. To this end, the standardization activities and use cases related to data sensing and communications in the smart grid are summarized. Finally, several open issues and challenges are outlined. Copyright © 2012 John Wiley & Sons, Ltd.

This article presents a tutorial on the sensor data collection, communications, and networking issues for the smart grid. The communication technologies and the data communication network architecture and protocols for the smart grid are described. Next, different emerging techniques for data sensing, communications, and sensor data networking are reviewed.

The packet loss burstiness over wireless channels is commonly acknowledged as a key impacting factor on the performance of networking protocols. An accurate evaluation of the packet loss burstiness, which reveals the characteristics and performance of the wireless channels, is crucial to the design of wireless systems and the quality-of-service provisioning to end users. In this paper, a simple yet accurate analytical framework is developed to dimension the packet loss burstiness over generic wireless channels. In specific, we first propose a novel and effective metric to characterize the packet loss burstiness, which is shown to be more compact, effective, and accurate than the metrics proposed in existing literature for the same purpose. With this metric, we then develop an analytical framework and derive the closed-form solutions of the packet loss performance, including the packet loss rate and the loss-burst/loss-gap length distributions. Lastly, as an example to show how the derived results can be applied to the design of wireless systems, we apply the analytical results to devise an adaptive packetization scheme. The proposed packetization scheme adaptively adjusts the packet length of transmissions based on the prediction of the packet loss rate and loss-burst/loss-gap lengths of the wireless channel. Via extensive simulations, we show that with the proposed packetization scheme, the channel throughput can be enhanced by more than 10% than the traditional scheme.Copyright © 2012 John Wiley & Sons, Ltd.

By segmenting the wireless channel as shown in the figure, we develop a simple yet accurate analytical framework to dimension the packet loss burstiness over generic wireless channels. In specific, we first propose a novel and effective metric to characterize the packet loss burstiness. Based on this metric, we then develop an analytical framework and derive the closed-form solutions of the packet loss performance, including the packet loss rate and the loss-burst/loss-gap length distributions.

Although extensive research has been carried out on the issue of how to optimally select relays in wireless relay networks, relay selection for mobile users is still a challenging problem because of the requirement that the dynamic selection should adapt to user mobility. Moreover, because the selected relays consume their energy on relaying data for the users, it is required that the users have to pay for this relay service. The price of selecting relays will affect the users' decisions. Assuming that different relays can belong to different service providers, we consider the situation that the service providers can strategically set the prices of their relays to maximize their profits. In this paper, we jointly study the dynamic relay selection for mobile users and profit maximization for service providers. Also, we design a Stackelberg-game hierarchical framework to obtain the solution. At the lower level, we investigate the relay selection problem for the mobile users under given prices of selecting the relays. It is formulated as a Markov decision process problem with the objective to minimize the mobile user's long-term average cost (which consists of the payment to the relay service and the cost due to packet loss), and solved by applying the linear programming technique. At the upper level, we study the game of setting relay prices for the service providers, with the knowledge that the mobile users will make relay selections based on their given prices. Nash equilibrium is obtained as the solution. Our results can help to provide a guidance for service providers to compete for providing relay services. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we jointly study the dynamic relay selection for mobile users and profit maximization for service providers. Also, we design a Stackelberg-game hierarchical framework to obtain the solution. The lower level is modeled as a Markov decision process problem for the mobile users, whereas the upper level is formulated as a non-cooperative game for the service providers, with Nash equilibrium as the solution. Our results can provide guidance for service providers to compete for providing relay services.

A global trend toward large scale emergencies has placed an emphasis on the achievement of a ubiquitous public safety network. Such a network may be realized over a mobile ad hoc network formed by the handheld mobile devices. Therefore, traffic in the network can be user generated and thus semantic. Unfortunately, none of the traffic management techniques proposed for the underlying network considers the semantic properties of the generated traffic. Therefore, in this paper, we propose a semantic traffic management framework which has two modules: traffic monitoring unit and traffic reduction unit. Although the first module analyzes the semantic traffic to detect an emergency, the latter module removes redundant semantic information for traffic reduction. We have supported the feasibility of the proposed semantic framework through simulation. Simulation results suggest that the framework is capable of accurate and early detection of an emergency as well as traffic reduction while keeping sufficient information to report the emergency. Copyright © 2012 John Wiley & Sons, Ltd.

Realization of a ubiquitous public safety network is crucial and can be accomplished over a mobile ad hoc network. Nonetheless, traffic in such a network is often user-generated and thus semantic. Hence, this paper proposes a semantic framework to manage the aforementioned semantic traffic such that it detects an emergency accurately, that is, up to 98%, via semantic traffic monitoring as well as removes related redundant traffic efficiently, that is, at least 90%, through semantic traffic reduction.

Energy-efficient routing becomes one of the most critical technologies for sustaining the overall network lifetime of wireless sensor networks. In this paper, we propose a novel data transmission scheme between a number of specified source nodes and the single sink, which can efficiently restrict the usage frequency of each relay node, measured by the number of source nodes using it for data transmission. On the basis of the importance of source nodes that is closely related to deployed location, they form a descending sequence such that each node finds the minimum energy path earlier than the succeeding one. Then, the energy-efficient multiple path algorithm with the computational complexity of O(n³) is developed for deriving the minimum energy paths, where n is the number of nodes in the network. Also, a polynomial algorithm is presented for deriving the range of the feasible values of N₀ serving as the threshold of the usage frequency of relay nodes, in which each can guarantee the existence of the solution. Further, we theoretically investigate the existence of the solution and the tree-structured solution using m-ary tree. Extensive simulation results show that our proposed scheme can achieve significant performance enhancement. Copyright © 2012 John Wiley & Sons, Ltd.

This paper proposes a data transmission scheme for multi-source single-sink wireless sensor networks to extend the network lifetime, in which each source node determines the minimum-energy path from the source node to the sink node in the order of the importance of source nodes when performing the environment monitoring. With this data transmission scheme, the using times of each relay node can be effectively and efficiently restricted.

As a fundamental problem of wireless sensor networks, the minimal exposure path problem corresponding to the sensor network's worst-case coverage plays an important role in the applications for detecting intrusions. However, most existing works about minimal exposure path are based on omnidirectional sensors. In contrast, this paper studies the minimal exposure path problem for two different types of directional sensing models: the binary sector model and directional sensitivity model. For the binary sector model, we construct a special Voronoi diagram, called sector centroids-based Voronoi diagram, to transform the minimal exposure path problem from a continuous geometric problem into a discrete geometric problem. By using the sector centroids-based Voronoi diagram, we develop an approximate algorithm to find the minimal exposure path in the sensors deployment field. For the directional sensitive model, we formulate the minimal exposure path problem by using two sensing intensity functions: all-sensor intensity function and maximum-sensor intensity function and then generate two weighted grids to convert the minimal exposure path problem into two discrete geometric problems. On the basis of the aforementioned weighted grids, we also develop two approximation algorithms to find the minimal exposure path for the directional sensitive model. We conduct extensive experiment simulations to validate and evaluate our proposed models and algorithms. Copyright © 2012 John Wiley & Sons, Ltd.

As a fundamental problem of wireless sensor networks, the minimal exposure path problem corresponding to the sensor network's worst-case coverage plays an important role in the applications for detecting intrusions. This paper studies the minimal exposure path problem for two different types of directional sensing models: the binary sector model and directional sensitivity model.We construct a special Voronoi diagram and two weighted grids to transform the minimal exposure path problem from a continuous geometric problem into three discrete geometric problems and develop three approximate algorithms to find the minimal exposure path in the sensors deployment field.

The fractional Fourier transform (FRFT)—a generalization of the well-known Fourier transform (FT)—is a comparatively new and powerful mathematical tool for signal processing. Many results in Fourier analysis have currently been extended to the FRFT, including the ordinary convolution theorem. However, the extension of the ordinary convolution theorem associated with the FRFT has been developed differently and is still not having a widely accepted closed-form expression. In this paper, a generalized convolution theorem for the FRFT is proposed, and the dual of it is also presented. The ordinary convolution theorem and some of its existing extensions related to the FRFT are shown to be special cases of the derived results. Moreover, some applications of the derived results are presented. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, a generalized convolution theorem for the fractional Fourier transform (FRFT) is proposed. The dual of this theorem is also derived. The ordinary convolution theorem and some existing convolution theorems associated with the FRFT are shown to be special cases of the derived results. Moreover, some applications of the derived results are presented.

A wireless mesh network has been popularly researched as a wireless backbone for Internet access. However, the deployment of wireless mesh networks in unlicensed bands of urban areas is challenging because of interference from external users such as residential access points. We have proposed Urban-X, which is a first attempt towards multi-radio cognitive mesh networks in industrial, scientific, and medical bands. Urban-X first controls network topology with a distributed channel assignment to avoid interference in large timescale. In such a topology, we develop a new link-layer transmission-scheduling algorithm together with source rate control as a small-timescale approach, which exploits receiver diversity when receivers of multi-flows can have different channel conditions because of varying interference. For this purpose, mesh nodes probe the channel condition of received mesh nodes using group Request to Send and group Clear to Send. In this study, we establish a mathematical Urban-X model in a cross-layer architecture, adopting a well-known network utility maximization framework. We demonstrate the feasibility of our idea using a simulation on the model. Simulation results show improved network throughput from exploiting receiver diversity and distributed channel assignment under varying external user interference. Copyright © 2012 John Wiley & Sons, Ltd.

Urban-X is a roofnet that consists of cognitive mesh nodes with multi-radios and primary nodes, such as residential wireless local area network access points, in industrial, scientific, and medical bands. In this study, we develop a new linklayer transmission-scheduling algorithm together with source rate control, which exploits receiver diversity by probing channel conditions using group Request to Send and Clear to Send when receivers of multi-flows have different channel conditions because of varying interference. We establish a mathematical model of our approach based on the network utility maximization framework.

Anonymous channel tickets have been proposed as a way to provide user anonymity and to reduce the overhead of re-authentication for authentication in wireless environments. Chen et al. proposed a secure and efficient protocol, based on a protocol proposed by Yang et al., which is resistant to guessing attacks on networks from which users’ secret keys are easy to obtain. However, their scheme is time-consuming in the phases of ticket issuing and authentication. Furthermore, a malicious attacker can utilize the expired time, T_exp, to launch a denial of authentication (DoA) attack, which is a type of denial of service attack. Because T_exp is exposed to any user, it would be easy to launch a DoA attack that could make the scheme impractical. To resist against DoAs that the scheme of Chen et al. might suffer, we propose an improved scheme based on elliptic curve cryptography in this paper. Our scheme not only reduces time cost but also enhances security. The basis of the proposed scheme is the elliptic curve discrete logarithm problem. The operations of points of an elliptic curve are faster and use fewer bits to achieve the same level of security. Therefore, our scheme is more suitable for mobile devices, which have limited computing power and storage. Copyright © 2012 John Wiley & Sons, Ltd.

Anonymous channel tickets have been proposed to provide user anonymity and to reduce the overhead of re-authentication in wireless environments. Chen et al. proposed a secure and efficient protocol based on that of Yang et al. However, the scheme is time-consuming in ticket issuing/authentication phases, and an attacker can use the expired time, T_exp, to launch a denial of authentication attack making the scheme impractical. On the basis of elliptic curve cryptography, our proposed scheme not only reduces time cost but also resist against DoAs.

In this paper, we propose a relatively complete and robust optimization model under the scenario where multisecondary users cooperatively sense multi-channels. The objective of this model is to maximize the system throughput, meanwhile aims to jointly optimize the parameters including the sensing time and the weight coefficients of the sampling results. Because this model is a nonlinear optimization model, we instead adopt a heuristic sequential parameters optimization method (SPO) to solve the model. The method begins with deriving the lower bound of the objective function of the optimization model. Then, it maximizes this lower bound by optimizing the weight coefficients through solving a series of suboptimal problems using Lagrange method. Given that the weight coefficients are found, it finally transforms the problem into another monotonic programming problem and exploits a fast-convergent polyblock algorithm to find an optimized sensing time parameter. We finally conduct extensive experiments by simulations. The results demonstrate that, in terms of the throughput gained by the system, SPO can deliver a solution that is up to 99.3% of the optimal on average, which indicates that SPO can solve the proposed optimization model effectively. In addition, we also show the performance advantage of the proposed model on improving the system throughput by comparing with other state-of-the-art optimization models. Wireless Communications and Mobile Computing.Copyright © 2012 John Wiley & Sons, Ltd.

We propose an optimization model under the scenario where multisecondary users cooperatively sense multi-channels. The objective of this model is to maximize the system throughput, meanwhile jointly optimize the parameters including the sensing time and the weight coefficients of each sampling results. We adopt a sequential parameter optimization method to solve the proposed model. The simulation results demonstrate the effectiveness of sequential parameter optimization and verify the advantage of the proposed model on improving the system throughput.

A closed-loop multiple-input multiple-output (MIMO) transceiver combining space–time multilayer precoding and transmit selection is proposed. The transmitter design consists in optimizing the number of space–time transmit layers as well as the partitioning of the transmit antennas into the selected number of space–time layers. We show that this problem can be translated into jointly selecting, from a finite alphabet, two transmit matrices that define, respectively, the multilayer space–time code and the antenna mapping to be used. The parametrization of the proposed design takes into account all possible space–time layering schemes in between spatial multiplexing and transmit diversity for a fixed number of transmit antennas and linear precoder structure. Sufficient conditions for solution existence using a linear space–time zero forcing receiver are discussed. Simulation results compare the proposed transceiver with some MIMO schemes and corroborate the benefits of closed-loop multilayer selection in terms of capacity and bit error rates. Copyright © 2012 John Wiley & Sons, Ltd.

A closed-loop MIMO transceiver is proposed to jointly optimize the number of space–time layers as well as the partitioning of the transmit antennas into the selected layers. The parametrization of the proposed design takes into account all possible space–time layering schemes in between spatial multiplexing and transmit diversity for a fixed number of transmit antennas and linear precoder structure.

Owing to the uncertainty of transmission opportunities between mobile nodes, the routing in delay tolerant networks (DTNs) exploits the mechanism of store-carry-and-forward. In this routing mechanism, mobility plays an important role, and we need to control the mobility of nodes around the network to help with carrying messages from the source to the destination. This is a difficult problem because the nodes in the network may move arbitrarily and it is difficult for us to determine when the nodes should move faster to help the data transmission while considering the complicated energy consumption in such a network. At the same time, for most DTNs, the system energy is limited, and energy efficient algorithms are crucial to maximizing the message delivery probability while reducing the delivery cost. In this paper, we investigate the problem of energy efficient mobility speed control in epidemic routing of DTN. We model the message dissemination process under variable mobility speed by a continuous-time Markov model. With this model, we then formulate the optimization problem of the optimal mobility control for epidemic routing and obtain the optimal policy from the solution of this optimization problem. Furthermore, extensive numerical results demonstrate that the proposed optimal policy significantly outperforms the static policy with constant speed, in terms of energy saving. Copyright © 2012 John Wiley & Sons, Ltd.

By modeling the message dissemination process under variable mobility speed in epidemic routing of delay tolerant network by a continuous-timeMarkov model, we investigate the problem of energy-efficient mobility speed control.With this model, we formulate the optimization problem of the optimal mobility control and obtain the optimal policy from the solution of this optimization problem. Extensive numerical results demonstrate that the proposed optimal policy significantly outperforms the static policy with constant speed, in terms of energy saving.

The two-dimensional (2D) block spread code division multiple access (CDMA) can avoid the uplink multiple-access interference with low-complexity single-user detection in a slow fading channel and, therefore, is very attractive. In the 2D spreading, orthogonal variable spreading factor (OVSF) is used for spreading; an important problem is how to efficiently assign the limited resource of OVSF codes to users with different data rates, while meeting the requirement of quality of service in a multi-cell environment. In this paper, it is shown that the code reuse can improve the code reuse efficiency and the proposed code reuse scheme combined with code assignment algorithm can allow flexible multi-rate uplink transmission. The computer simulation confirms that the proposed code assignment algorithm improves the code reuse efficiency while achieving lower blocking probability than traditional CDMA. Copyright © 2012 John Wiley & Sons, Ltd.

On the basis of two-dimensional block spread multi-cellular code division multiple access, which is used to avoid multiaccess interference, the proposed algorithm is able to support multi-services under the required quality of service with efficiency code reuse scheme.

Two new incremental models for online anomaly detection in data streams at nodes in wireless sensor networks are discussed. These models are incremental versions of a model that uses ellipsoids to detect first, second, and higher-ordered anomalies in arrears. The incremental versions can also be used this way but have additional capabilities offered by processing data incrementally as they arrive in time. Specifically, they can detect anomalies ‘on-the-fly’ in near real time. They can also be used to track temporal changes in near real-time because of sensor drift, cyclic variation, or seasonal changes. One of the new models has a mechanism that enables graceful degradation of inputs in the distant past (fading memory). Three real datasets from single sensors in deployed environmental monitoring networks are used to illustrate various facets of the new models. Examples compare the incremental version with the previous batch and dynamic models and show that the incremental versions can detect various types of dynamic anomalies in near real time. Copyright © 2012 John Wiley & Sons, Ltd.

We propose two new incremental models (iterative data capture anomaly detection (IDCAD) and forgetting factor (FFIDCAD)) for anomaly detection that identify temporal changes in streaming data. These models are compared with a batch (DCAD) and an autoregressive (ARX/RLS) model. The red points in the figure compare the first-order anomalies found in the data at a node of the Intel Berkeley Research Lab wireless sensor network that drifts due to battery failure found by the batch DCAD model with those found by the incremental FFIDCAD model with a forgetting factor.

An approach of superimposed training (ST)-aided time-varying (TV) channel estimation for multiple-input multiple-output orthogonal frequency division multiplexing systems is presented. By modeling the TV channel with the truncated discrete basis expansion model, a two-step approach is adopted to estimate the TV channel. In addition, the mean square error (MSE) of the proposed channel estimation is analyzed, and its closed-form expression is derived, which is a function of the data-to-ST power ratio. Using the developed channel MSE, we case the problem of ST power-allocation by minimizing the lower bound on the average channel capacity. To enhance the performance of channel estimation, a low-complexity decision feedback mechanism is introduced to iteratively mitigate the unknown data interference. Numerical results verify the performances of the proposed approach. Copyright © 2012 John Wiley & Sons, Ltd.

An approach of superimposed training-based time-varying channel estimation for MIMO OFDM systems is investigated. By modeling the channel as truncated discrete Fourier bases, channel estimation is performed by a two-step procedure, from which optimal training-to-data power allocation is derived. To further enhance the performance of channel estimation, a decision-feedback mechanism is introduced by using sub-block tracking. Numerical results verify the performance of the proposed algorithms.

For many applications, it is desirable for a node to be able to identify the neighbor nodes currently within range. However, the identification procedures for terrestrial communication networks (TCNs) are inefficient when implemented in long-delay networks (LDNs) such as underwater acoustic networks or satellite networks, where the propagation time of a packet cannot be neglected. Here, we propose a time-efficient and power-efficient procedure, which is insensitive to propagation delay, for identifying neighbors in an LDN by optimizing the network offered load using either unslotted or slotted protocols. The procedure is adapted to the scenario when node cardinality and distribution are either known or unknown in advance. We achieve improvements as high as 80% in time and 45% in power consumption for our proposed approach compared with approaches developed previously for TCN. Furthermore, we analyze our proposed approach with the inclusion of the capture effect and packet receive time variations. We also provide a closed form formula for finding the optimum guard time and a procedure to estimate the packet receive time variations. Copyright © 2012 John Wiley & Sons, Ltd.

Propagation delay insensitive identification procedures for a node in a long-delay-network have been proposed here to gather the identities of the neighboring nodes. The network offered load is optimized for both slotted and un-slotted procedures to achieve improvements of 80% in time and 45% in power consumption in relative to the approaches proposed for terrestrial communication networks. The proposed approaches are analysed with known and unknown numbers of neighbors, with inclusion of capture effect and packet receive time variations.

There is growing interest in the use of wireless mesh network (WMN) as a last-mile option for Internet access. Despite the many benefits of WMNs, the performance of Internet access may not be ideal. One of the main issues is the interaction of transmission control protocol (TCP) with the underlying network. The poor performance of TCP over multi-hop networks is well-documented, and extensive research exists, which addresses TCPs foible and enhance TCP performance for multi-hop environments. This paper provides a thorough survey of TCP performance issues over WMNs and the available solutions to address these issues. Among the existing methods, we focused on network coding (NC) and the ways that TCP interacts with network coded systems. NC is a technique that encodes the received packets in each node before forwarding them towards the destination. The use of NC in the transport layer to address performance issues raised by wireless access is a recent research topic. This paper presents a detailed study of TCP interaction with NC. Some open research areas in this field are suggested. Copyright © 2012 John Wiley & Sons, Ltd.

This paper presents a detailed study of transmission control protocol interaction with network coding. Some open research areas in this field are suggested.

This paper provides a measurement-based performance evaluation of the Optimized Link State Routing (OLSR) protocol. Two versions of OLSR, OLSR-ETX and OLSR-ETT, are implemented and evaluated on a mesh network that we built from off-the-shelf commercial components and deployed within our department building. OLSR-ETX uses the Expected Transmission Count (ETX) metric, whereas OLSR-ETT uses the Expected Transmission Time (ETT) metric as a means of assessing link quality. The paper describes our implementation process of the ETT metric using the plug-in feature of OLSRd, and our calculation method of link bandwidth using the packet-pair technique. A series of measurements are conducted in our testbed to analyze and compare the performance of ETX and ETT metrics deemed useful for quality of service. Our measurements show that OLSR-ETT outperforms OLSR-ETX significantly in terms of packet loss, end-to-end delay, jitter, route changes, bandwidth, and overall stability, yielding much more robust, reliable, and efficient routing. Copyright © 2012 John Wiley & Sons, Ltd.

This work implements and evaluates the performance of the OLSR protocol on a wireless mesh network, built from off-the-shelf commercial components at Oregon State University. Two versions of OLSR were implemented, tested, and evaluated: OLSR-ETX and OLSR-ETT. Tests were performed to analyze and evaluate the stability achieved by the respective metrics and emphasize the importance of bandwidth detection and its effect on network stability. Our measurements show that OLSR-ETT outperforms OLSR-ETX significantly in terms of packet loss, end-to-end delay, and stability.

Protocols for sensor networks have traditionally been designed using the best effort delivery model. However, there are many specific applications that need reliable transmissions. In event-driven wireless sensor networks, the occurrence of an event may generate a large amount of data in a very short time. Among them, some critical urgent information needs to be transmitted reliably in a timely manner. In this scenario, congestion is inevitable because of the constraints in available resources. How to control the congestion is very important for the reliable transmission of urgent information. To address this problem, we propose a queue-based congestion detection and a multistage rate control mechanism. In our proposed mechanism, not only the current queue length but also the queue fluctuation are adopted as indications of congestion. Each sensor node evaluates its congestion level locally and determines its congestion state with a state machine. We design a multistage rate adjustment mechanism for nodes to adjust their rates depending on their congestion states. We also distinguish high-priority critical traffic from low-priority non-critical traffic. Extensive simulation results confirm the superior performance of our proposed protocol with respect to throughput, loss probability, and delay.Copyright © 2012 John Wiley & Sons, Ltd.

In event-driven wireless sensor networks, we propose a queue-based congestion detection and a multistage rate control mechanism. In our proposed mechanism, not only the current queue length but also the queue fluctuation is adopted as indications of congestion. Each sensor node evaluates its congestion level locally and determines its congestion state with a state machine. We design a multistage rate adjustment mechanism for nodes to adjust their rates depending on their congestion states.

Query scheduling as one of the most important technologies used in query processing has been widely studied recently. In this paper, we investigate the Minimum Latency Multi-Regional Query Scheduling (ML-MRQS) problem in wireless Sensor Networks (WSNs), which aims to generate a scheduling plan with minimum latency under a more practical query model called Multi-Regional Query (MRQ). An MRQ targets at interested data from multiple regions of a WSN, where each region is a subarea. Because the ML-MRQS problem is NP-hard, we propose a heuristic scheduling algorithm Multi-Regional Query Scheduling Algorithm (MRQSA) to solve this problem. Theoretical analysis shows that the latency of MRQSA is upper bounded by 23A + B + C for an MRQ with m query regions , where is the maximum latency for non-overlapped regions, is the maximum latency for overlapped regions, and is the accumulated latency for data transmission from the accessing nodes to the sink. Simulation results show that MRQSA reduces latency by 42.7% to 51.63% with respect to different number of query regions, network density, region size, and interference/transmission range compared with C-DCQS, while guaranteeing energy efficiency. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we investigate the Minimum Latency Multi-Regional Query Scheduling (ML-MRQS) problem in Wireless Sensor Networks (WSNs), which aims to generate a scheduling plan with minimum latency under a more practical query model called Multi-Regional Query (MRQ). Because the ML-MRQS problem is NP-hard, we propose a heuristic scheduling algorithm Multi-Regional Query Scheduling Algorithm (MRQSA) to solve this problem. Theoretical analysis shows that the latency of MRQSA is upper bounded. Simulation results show the good performance of MRQSA.

In this paper, a new model utilizing all the information derived from connectivity-based sensor network localization is introduced. The connectivity information between any pair of nodes is modeled as convex and non-convex constraints. The localization problem is solved by searching for a solution that would satisfy all the constraints established in the problem. A two-objective evolutionary algorithm called Pareto Archived Evolution Strategy (PAES) is used to solve the localization problem. The solution can reach the most suitable configuration of the unknown nodes because the information on both convex and non-convex constraints related to connectivity has been utilized. From simulation results, a relationship between the communication range and accuracy is obtained. Furthermore, a two-level range connectivity-based sensor network localization method is proposed to enrich the connectivity information. The two-level range/indication of connectivity between each pair of nodes would indicate three levels of connectivity: strong, weak, or nil. A comparison on accuracy between the one-level and two-level ranges of connectivity is carried out by simulation using six different topological networks all containing 100 nodes. Simulation results have shown that better solution can be obtained by using two-level range connectivity compared with the usual one-level range connectivity-based localization. Copyright © 2012 John Wiley & Sons, Ltd.

A new model utilizing all the information derived from connectivity-based sensor network localization is introduced. The connectivity information between any pair of nodes is modeled as convex and non-convex constraints. The localization problem is solved by searching for a solution that would satisfy all the constraints established in the problem. Furthermore, a two-level range connectivity-based sensor network localization method is proposed to enrich the connectivity information.

The growing popularity of mobile devices in our daily life demands higher throughput of wireless networks. The new communication standard 802.11n has significantly improved throughput because of the use of advanced technologies such as the multiple-input multiple-output communication technique. Because mobile devices are usually battery-operated, power efficiency is critical; on the other hand, delay performance can be improved by transmitting at high power. To address the conflicting requirement of power saving and small delay, power scheduling is needed. In the past, many approaches to power scheduling have been proposed for real-time applications, but few of them have considered complicated modes of channel state information(CSI) in multiple-input multiple-output. In this paper, we study this and classify the CSI into four types, namely, constant, slow fading, fast fading, and unknown. For known CSI, we propose an optimal algorithm for power scheduling. For unknown CSI, we propose an approximate algorithm based on some heuristics. To improve resource utilization, a stochastic delay-bound method is proposed for fast-fading condition. Simulation results demonstrate that the performance achieved by the optimal and heuristic algorithms agrees well with the analysis. Copyright © 2012 John Wiley & Sons, Ltd.

This paper studies the optimal power scheduling in multiple-input multiple-output channel under four channel state information conditions, that is, constant, slowing fading, fast fading, and unknown. Problem formulation, optimization solution, and complexity analysis are presented under each condition. Simulation results show that the performance matches well with expectation.

Data/content dissemination among the mobile devices is the fundamental building block for all the applications in wireless mobile collaborative computing, known as mobile peer-to-peer. Different parameters such as node density, scheduling among neighboring nodes, mobility pattern, and node speed have a tremendous impact on data diffusion in a mobile peer-to-peer environment. In this paper, we develop analytical models for object diffusion time/delay in a wireless mobile network to apprehend the complex interrelationship among these different parameters. In the analysis, we calculate the probabilities of transmitting a single object from one node to multiple nodes using the epidemic model of spread of disease. We also incorporate the impact of node mobility, radio range, and node density in the networks into the analysis. Utilizing these transition probabilities, we estimate the expected delay for diffusing an object to the entire network both for single object and multiple object scenarios. We then calculate the transmission probabilities of multiple objects among the nodes in the wireless mobile network considering network dynamics. Through extensive simulations, we demonstrate that the proposed scheme is efficient for data diffusion in the wireless mobile network. Copyright © 2012 John Wiley & Sons, Ltd.

This paper introduces analytical models for object distribution time/delay in a wireless mobile network utilizing epidemic disease-spreading methods. These analytical models apprehend the complex interrelationship among different parameters such as node density, scheduling among neighboring nodes, mobility pattern, and node speed in a mobile peer-to-peer environment.

The capacity of wireless networks can be improved by the use of multi-channel multi-interface (MCMI), multi-packet reception (MPR), and directional antenna (DA). MCMI can provide the concurrent transmission in different channels for each node with multiple interfaces; MPR offers an increased number of concurrent transmissions on the same channel; DA can be more effective than omni-DA by reducing interference and increasing spatial reuse. This paper explores the capacity of wireless networks that integrate MCMI, MPR, and DA technologies. Unlike some previous research, which only employed one or two of the aforementioned technologies to improve the capacity of networks, this research captures the capacity bound of the networks with all the aforementioned technologies in arbitrary and random wireless networks. The research shows that such three-technology networks can achieve at most capacity gain in arbitrary networks and capacity gain in random networks compared with MCMI wireless networks without DA and MPR. The paper also explored and analyzed the impact on the network capacity gain with different , θ, and k-MPR ability. Copyright © 2012 John Wiley & Sons, Ltd.

The capacity of wireless networks can be improved by the use of multi-channel multi-interface, multi-packet reception, and directional antenna. Unlike some previous research, which only employed one or two of the aforementioned technologies to improve the capacity of networks, this paper captures the capacity bound of the networks with all the aforementioned technologies in arbitrary and random wireless networks.

This article focuses on improving the system capacity of 60-GHz wireless personal area networks (WPANs) and presents an effective time slot allocation scheme for spatial reuse, which combines the existing exclusive region (ER)-based scheduling algorithm with simple power control. In the study, the concept of ER for concurrent transmissions is introduced first. Considering the large path loss in the millimeter-wave band and the characteristics of typical indoor multipath channels, we generalize the signal propagation model as well as ER radius for 60-GHz WPANs. Then, we propose an improved ER-based scheduling algorithm, which employs power control instead of constant transmitting power. In this algorithm, devices are assumed to receive data at the receiver sensitivity, which refers to the minimum receiving power to ensure the reliability for communications. Implementation feasibility is provided within the current standards framework. Some more practical analysis based on the beamforming codebook specified by of the IEEE 802.15.3c standard is also developed. In addition, the impact of the antenna radiation efficiency and receiver sensitivity is discussed. Computer simulations validate the excellent performance of the proposed scheme, which can significantly improve the channel capacity under different antenna configurations. Copyright © 2012 John Wiley & Sons, Ltd.

This article focuses on improving the system capacity of 60 GHz wireless personal area networks and presents an effective timeslot allocation scheme for spatial reuse, which combines the existing exclusive region-based scheduling algorithm with simple power control. Extensive computer simulations were evaluated with the consideration of beamforming technology, which show the excellent performance of the proposed scheme that can significantly improve the channel capacity under different antenna configuration.

In wireless sensor networks, achieving load balancing in an energy-efficient manner to improve the network lifetime as much as possible is still a challenging problem because in such networks, the only energy resource for sensor nodes is their battery supplies. This paper proposes a game theoretical-based solution in the form of a distributed algorithm for constructing load-balanced routing trees in wireless sensor networks. In our algorithm, load balancing is realized by adjusting the number of children among parents as much as possible, where child adjustment is considered as a game between the parents and child nodes; parents are considered as cooperative players, and children are considered as selfish players. The gained utility by each node is determined by means of some utility functions defined per role, which themselves determine the behavior of nodes in each role. When the game is over, each node gains the maximum benefit on the basis of its utility function, and the balanced tree is constructed. The proposed method provides additional benefits when in-network aggregation is applied. Analytical and simulation results are provided, demonstrating that our proposed algorithm outperform two recently proposed benchmarking algorithms [1, 2], in terms of time complexity and communication overhead required for constructing the load-balanced routing trees. Copyright © 2012 John Wiley & Sons, Ltd.

A game theoretical-based distributed algorithm for constructing load-balanced routing trees in wireless sensor networks is proposed. Load balancing is realized by optimally adjusting the number of children among parents, where parents are considered as cooperative players and children are considered as selfish players. The proposed algorithm provides additional benefits when in-network aggregation is applied. Analytical and simulation results in terms of time complexity and communication overhead required for constructing the trees are also provided.

In this paper, we investigate the optimal sensing settings for a cognitive radio (CR) network consisting a number of CR users and a fusion center (FC). Our objective is to maximize the channel utilization under the constraint that the signals from the primary user (PU) are sufficiently protected. We focus on the utilization of the channel in which PUs dynamically enter the network with burst nature. Thus, we apply the average error probability (AEP) as the metric of channel utilization. Moreover, in order to protect the PU signal from being interfered, the missing detection probability is applied as the constraint function. Assuming that counting rules are utilized in the FC, we derive the false alarm probability, the missing detection probability, and the AEP in the maximum a posteriori (MAP) fashion. Then, after proving the monotonic properties of the objective function and the constraint function, we propose an efficient algorithm named Algorithm I that can derive the optimal settings for maximizing the channel utilization. Moreover, a simplified algorithm named Algorithm II is also proposed to minimize the AEP, supposing that perfect synchronization exists between the CR users and the PU. Finally, we show our numerical results and compare our optimal results with those found by exhaustive searches. We conclude that our Algorithm I produces optimal results very close to those found by exhaustive searches. Performance comparison between Algorithms I and II is also provided in terms of the AEP and the probability of missing detection. Copyright © 2012 John Wiley & Sons, Ltd.

This paper considers the optimization of the cooperative spectrum sensing when the primary user accesses or departs the channel randomly. An efficient algorithm is proposed to evaluate the optimal sensing settings so that the channel utilization is maximized. The proposed algorithm is shown to be able to produce the optimal results very close to those found by exhaustive searches.

Satellite-based apositioning and navigation technology in urban environments is widely studied. As a solution to GPS signal degradation in urban environment, the wireless network-aided location scheme has been put into practice, which benefits our everyday life. However, there still exist many potential advantageous points that can be exploited to improve the performance of the location service especially in urban environments. This paper proposes a GPS-based positioning and navigation with the aid of wireless network (GPONAWIN) positioning scheme that utilizes the existing resources of wireless communication networks to provide cheaper and more accurate urban positioning service with higher survivability. After the proposed scheme is described in detail, outperformances over the existing scheme are also analyzed. The GPONAWIN scheme can achieve higher information utilization efficiency, less wireless channel expenditure, more accurate positioning, better expandability to the multiple satellite positioning and navigation systems, and lower cost. Copyright © 2012 John Wiley & Sons, Ltd.

The urban positioning technology based on the combination of GPS and the wireless communication system is improved. The useless assisting information from the mobile stations is reduced; the more wireless channel resources are saved; the positioning accuracy is improved by satellite constellation optimization; and the existing and improving global satellite positioning systems are considered to improve the survivability.

This paper proposes a novel method to detect the number of two-dimensional (2D) harmonics in additive colored noise based on the enhanced covariance matrix. We define an enhanced covariance matrix using the covariances of the observed signal. We get a special inherent relation between the number of 2D harmonics in additive colored noise and the eigenvalues of the enhanced covariance matrix, which can be used to detect the number of 2D harmonics in additive colored noise by analyzing the eigenvalues of the enhanced covariance matrix. The proposed method has a super resolution and does not need to assume the color and distribution of the additive noise. The effectiveness of the proposed method has been validated by both the theoretical analysis and extensive simulations. Copyright © 2012 John Wiley & Sons, Ltd.

This paper proposes a novel method to detect the number of two-dimensional harmonics in additive colored noise based on the enhanced covariance matrix. The proposed method can efficiently detect the number of two-dimensional harmonics in additive noise. Moreover, the proposed method has a super resolution and does not need the the prior knowledge of the color and distribution of the additive noise.

This paper analyzes the performance bounds of a wireless relay system consisting of several relay stations working on both amplifier-and-forward (AF) and decode-and-forward (DF) protocols. We want to study the outage probability behavior of the proposed mixed AF and DF relay systems under independent Nakagami-m fading channels. In particular, we will derive the lower and upper bounds of outage probability of the mixed AF and DF relay systems based on maximal ratio combining diversity reception. The results give optimal configuration of AF and DF relays under a specific channel condition, thus helping us to design an optimized mixed AF and DF relay system in a generic fading environment. The trade-off between complexity and performance is discussed in this paper. In addition, we will use computer simulations to verify the effectiveness of the proposed mixed AF and DF relay configurations. Finally, the power allocation issues for such a mixed AF and DF relay system will also be discussed. Copyright © 2012 John Wiley & Sons, Ltd.

The results obtained in this article show the ways on how to configure an optimal mixed AF and DF relays system under a specific channel condition. The trade-off between complexity and performance is discussed in this article. In addition, computer simulations were used to verify the effectiveness of the proposed mixed AF and DF relay configurations. Finally, the power allocation issues for such a mixed AF and DF relay system will also be discussed.

The signal of a hypersonic spacecraft entering the Earth's atmosphere may be lost at a certain altitude transitorily. This phenomenon is called “blackout,” an important performance feature of aircraft design. Recently, with the development of the nearcraft, communication techniques under the plasma environment have increasingly become more important, with the realization that we can record, monitor, track, and capture the nearcraft. In this paper, an idea based on the capability of radiation from the terahertz communication system to penetrate the plasma sheath is proposed to provide the theoretical basis for real-time communication with the nearcraft. Copyright © 2012 John Wiley & Sons, Ltd.

Terahertz communication is used in the plasma condition, which cannot communicate by using traditional method.

In this paper, we propose a new compressive sensing-based compression and recovery ultra-wideband (UWB) communication system. Compared with the conventional UWB system, we can jointly estimate the channel and compress the data, which can also simplify the design of hardware. No information about the transmitted signal is required in advance as long as the channel follows autoregressive process. As an application example, real-world UWB signal is collected and processed to evaluate the performance of our proposed system. The compression procedure is so simple that we just multiply random Gaussian or Bernoulli matrix with the original data to capture all the information we want. Simulation results show that the data could be perfectly recovered if the compression ratio does not exceed 2.5:1 when Bernoulli matrix is chosen as the sensing matrix. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we propose a new compressive sensing-based compression and recovery ultra-wideband (UWB) communication system. Compared with the conventional UWB system, we can jointly estimate the channel and compress the data, which also simplify the design of hardware. No information about the transmitted signal is required in advance as long as the channel follows autoregressive process.

The traditional equalization technologies expose some shortages while people put forward higher demand to quality of communication system and transmission rate. Single-carrier frequency-domain equalization (SC-FDE) is becoming a research hotspot in wideband wireless communication area because of its special predominance. In recent years, the research on SC-FDE develops quickly. We take a study on feasibility of building SC-FDE system by comparing performance with orthogonal frequency division multiplexing. This paper takes a study on a dual-mode direct decision-least mean square+modify constant modulus algorithm blind equalization algorithm applied in a single-carrier system. And then, we build the simulation model of image transmission in SC-FDE system and get the direct and better result through the comparative analysis of image. Copyright © 2012 John Wiley & Sons, Ltd.

This paper takes a study on a dual-mode direct decision-leastmean square+modify constant modulus algorithm blind equalization algorithm applied in a single-carrier system.We build the simulation model of image transmission in single-carrier frequency-domain equalization system and get the direct and better result through the comparative analysis of image.

A hop-aware and energy-based buffer management scheme (HEB) is proposed in this paper. HEB can provide better quality of service to packets with real-time requirements and improve MANET power efficiency. In our algorithm, the buffer is divided into real-time and non-real-time partitions. We consider the number of hops passed, the power levels of the transmitting node, the predicted number of remaining hops, and waiting time in the buffer to determine packet transmission priority. In addition, specialized queue management and a probabilistic scheduling algorithm are proposed to decrease retransmissions caused by packet losses. Mathematical derivations of loss rates and end-to-end delays are also proposed. Coincidence between mathematical and simulation results is also shown. Finally, the HEB is compared with first in first out, random early detection, and hop-aware buffering scheme. Simulation results show that the proposed algorithm reduces loss rates, power consumption, and end-to-end delays for real-time traffic, considerably improving the efficiency of queue management in MANET. Copyright © 2012 John Wiley & Sons, Ltd.

The hop-aware and energy-based buffer management scheme utilizes the number of hops passed, power levels of the transmission node, the predicted remaining number of hops, and waiting time in the buffer to determine packet transmission priority. The results show that the algorithm has better performance than other methods.

In this paper, we study the delay performance in a wireless sensor network (WSN) with a cluster-tree topology. The end-to-end delay in such a network can be strongly dependent on the relative location between the sensors and the sink and the resource allocations of the cluster heads (CHs). For real-time traffic, packets transmitted with excessive delay are dropped. Given the timeline allocations of each CH for local and inter-cluster traffic transmissions, an analytical model is developed to find the distribution of the end-to-end transmission delay for packets originated from different clusters. Based on this result, the packet drop rate is derived. A heuristic scheme is then proposed to jointly find the timeline allocations of all the CHs in a WSN in order to achieve the minimum and balanced packet drop rate for traffic originated from different levels of the cluster tree. Simulation results are shown to verify the analysis and to demonstrate the effectiveness of the proposed CH timeline allocation scheme. Copyright © 2012 John Wiley & Sons, Ltd.

This paper studies end-to-end delay performance in a wireless sensor network (WSN) with a cluster-tree topology. An analytical model is developed to find the distribution of the end-to-end transmission delay, based on which packet drop rate is derived for traffic originated from different clusters. A heuristic scheme is proposed to jointly find the timeline allocations of all the cluster heads in order to achieve the minimum and balanced packet drop rate in different clusters.

In this paper, end-to-end performance of transmit antenna selection (TAS) and generalized selection combining (GSC) is studied in a dual-hop amplify-and-forward relay network over flat Rayleigh fading channels. In the system, source and destination equipped with multiple antennas, communicate by the help of single relay equipped with single antenna. Source-destination link is not available. TAS is used for transmission at the source, and GSC is used for reception at the destination. By considering the relay location and the presence of error in feedback channel from the relay to the source, we derive closed-form outage probability, moment generating function and moments of end-to-end signal-to-noise ratio, and closed-form symbol error probability (SEP) expressions for channel state information (CSI)-based and fixed relay gains. The diversity order and array gain of the network are obtained for both CSI-based and fixed relay gains by deriving asymptotical outage probability and SEP expressions. The analytical results are validated by the Monte Carlo simulations. Copyright © 2012 John Wiley & Sons, Ltd.

Performance of transmit antenna selection and generalized selection combining is studied in a dual-hop amplify-andforward relay network over Rayleigh fading channels. Considering the relay location and the presence of error in feedback channel from the relay to the source, we derive closed-form outage probability, moment generating function and moments of end-to-end signal-to-noise ratio, and symbol error probability expressions for channel state information (CSI)-based and fixed relay gains. The diversity order and array gain of the network are obtained for both CSI-based and fixed relay gains.

Inspired by the backbone concept in wired networks, a virtual backbone is expected to bring substantial benefits to routing in wireless sensor networks (WSNs). A connected dominating set (CDS) is used as a virtual backbone for efficient routing and broadcasting in WSNs. Most existing works focus on constructing a minimum CDS, a k-connect m-dominating CDS, a minimum routing cost CDS, or a bounded-diameter CDS. However, the load-balance factor is not considered for CDSs in WSNs. In this paper, a greedy-based approximation algorithm is proposed to construct load-balanced CDS in a WSN. More importantly, we propose a new problem: the Load-balanced Allocate Dominatee problem. Consequently, we propose an optimal centralized algorithm and an efficient probability-based distributed algorithm to solve the Load-balanced Allocate Dominatee problem. For a given CDS, the upper and lower bounds of the performance ratio of the distributed algorithm are analyzed in the paper. Through extensive simulations, we demonstrate that our proposed methods extend network lifetime by up to 80% compared with the most recently published CDS construction algorithm. Copyright © 2012 John Wiley & Sons, Ltd.

Inspired by the backbone concept in wired networks, a virtual backbone is expected to bring substantial benefits to routing in wireless sensor networks (WSNs). A connected dominating set (CDS) is used as a virtual backbone for efficient routing and broadcasting in WSNs. Most existing works focus on constructing a minimum CDS, a k-connect m-dominating CDS, a minimum routing cost CDS, or a bounded-diameter CDS. However, the load-balance factor is not considered for CDSs in WSNs. In this paper, a greedy-based approximation algorithm is proposed to construct load-balanced CDS in a WSN. More importantly, we propose a new problem: the Load-balanced Allocate Dominatee problem. Consequently, we propose an optimal centralized algorithm and an efficient probability-based distributed algorithm to solve the Load-balanced Allocate Dominatee problem. For a given CDS, the upper and lower bounds of the performance ratio of the distributed algorithm are analyzed in the paper. Through extensive simulations, we demonstrate that our proposed methods extend network lifetime by up to 80% compared with the most recently published CDS construction algorithm.

This paper performs a comparison of multicast/broadcast services (MBS) support in Long Term Evolution Advanced (LTE-A) and Worldwide Interoperability for Microwave Access (WiMAX) IEEE 802.16m. Firstly, the main technical features of both standards concerning MBS operation are presented. It is shown that WiMAX offers higher unicast/MBS multiplexing flexibility as it supports both frequency and time multiplexing schemes, whereas LTE-A only includes time multiplexing. Besides, only WiMAX supports multi-antenna transmission. Next, the results of two simulation-based assessments are presented. In the former, it is considered a scenario with all cells transmitting the same MBS service. The effect of inter-site distance (ISD) on the maximum MBS data rate is evaluated. Results show that WiMAX configurations outperform LTE-A for small ISD. This is because WiMAX provides a higher number of resources dedicated to data transmission for the same bandwidth. Furthermore, some WiMAX configurations support two spatially multiplexed data streams. With higher ISDs, LTE-A outperforms single-stream WiMAX configurations. In the second assessment, a MBSFN area surrounded by interfering cells is considered to compare unicast/MBS multiplexing performance. The higher maximum MBS data rate is achieved in WiMAX with time division multiplexing, which is precisely the only alternative included in LTE-A.Copyright © 2012 John Wiley & Sons, Ltd.

This paper performs a comparison of multicast and broadcast services (MBS) configurations and unicast/MBS multiplexing options included in Long Term Evolution Advanced and Worldwide Interoperability for Microwave Access IEEE 802.16m. Results have shown that spatial multiplexing with two streams significantly increases the performance of the MBS transmission for the considered scenarios. It is also shown that time division multiplexing is the preferred option to multiplex unicast/MBS services in these scenarios as it fully exploits frequency diversity.

With recent advances in wireless networking and in low-power sensor technology, wireless sensor networks (WSNs) have taken significant roles in various applications. Whereas some WSNs only require minimal bandwidth, newer applications operate with a noticeably larger amount of data. One way to deal with these applications is to maximize the available capacity by utilizing multiple wireless channels. We propose DynaChannAl, a distributed dynamic wireless channel allocation algorithm that effectively distributes nodes to multiple wireless channels in WSNs. Specifically, DynaChannAl targets applications where mobile nodes connect to preexisting wireless backbones and takes the expected end-to-end queuing delay as its core metric. We used the link quality indicator values provided by 802.15.4 radios to whitelist high-quality links and evaluate these links with the aggregated queuing latency, making it useful for applications that require minimal end-to-end delay (i.e., health care). DynaChannAl is a lightweight and adoptable scheme that can be incorporated easily with predeveloped systems. As the first study to consider end-to-end latency as the core metric for channel allocation in WSNs, we evaluate DynaChannAl on a 45 node test bed and show that DynaChannAl successfully distributes source nodes to different channels and enables them to select channels and links that minimizes the end-to-end latency. Copyright © 2012 John Wiley & Sons, Ltd.

Single-carrier frequency domain adaptive antenna array (SC-FDAAA) has been proposed and proved in our previous study to be effective in suppressing multiple access interference in a severely frequency selective fading channel. In this paper, we studied the performance of SC-FDAAA in a distributed antenna network (DAN). To make it clear whether the performance of SC-FDAAA can benefit from the distributed nature of DAN or not, we made a comparison between DAN and the traditional cellular network, that is, central antenna network. The bit error rate distribution and the system capacity (both link capacity and cellular link capacity) are presented. It is shown that by using the SC-FDAAA, cellular link capacity is maximized by using single frequency reuse. In addition, the capacity of SC-FDAAA can also benefit from the distributed nature of DAN. Copyright © 2012 John Wiley & Sons, Ltd.

This paper studies the performance of single-carrier frequency domain adaptive antenna array (SC-FDAAA) in a distributed antenna network (DAN). A comparison between DAN and the traditional cellular network has been made. It is shown that by using the SC-FDAAA, cellular link capacity is maximized using single frequency reuse. In addition, the capacity of SC-FDAAA can also benefit from the distributed nature of DAN.

Spectrum sensing is defined as the task of detecting the presence of licensed users and is an essential prerequisite for opportunistic spectrum access in cognitive radio. Motivated by the infeasible assumptions of perfect synchronization and prior noise knowledge in most of the existing spectrum sensing algorithms, a robust orthogonal frequency division multiplexing (OFDM) signal sensing scheme, with the use of a noise power insensitive threshold, is investigated in this paper. Identification of primary OFDM signals is achieved by sliding the local pilot reference over the received signals and measuring the frequency domain correlations. The necessity of prior noise power knowledge for the sensing threshold determination is removed by employing the proposed interference insensitive test metric, which is a ratio of uniformly distorted correlations. As a result, no noise power information is required in the sensing process. In addition, the effects of both timing and frequency offsets are mitigated with a novel extended time domain segmentation as well as multiple frequency domain correlations via a frequency sliding window. Numerical results are provided to validate the theoretical analysis and estimate the performance of the proposed algorithm. Copyright © 2012 John Wiley & Sons, Ltd.

A robust orthogonal frequency division multiplexing spectrum sensing technique using a noise power insensitive threshold is investigated in this paper. Identification of primary orthogonal frequency division multiplexing signals is achieved by sliding the local pilot reference over the received signals and measuring the frequency domain correlations. The impact of timing offset is mitigated using an extended time domain signal segmentation, and the frequency offset is combatted using frequency domain correlations by applying a sliding frequency window.

Recent advances in body area network technologies such as radio frequency identification and ham radio, to name a few, have introduced a huge gap between the use of current wireless sensor network technologies and specific needs of some important wireless sensor network applications such as medical care, disaster relief, or emergency preparedness and response. In these types of applications, the mobility of nodes can occur, leading to the challenge of mobility handling. In this paper, we address this challenge by prioritizing transmissions of mobile nodes over static nodes. This is achieved by using shorter contention windows in reservation slots for mobile nodes (the so-called backoff technique) combined with a novel hybrid medium access control (MAC) protocol (the so-called versatile MAC). The proposed protocol advocates channel reuse for bandwidth efficiency and management purpose. Through extensive simulations, our protocol is compared with other MAC alternatives such as time division multiple access and IEEE 802.11 with request to send/clear to send exchange, chosen as benchmarks. The performance metrics used are bandwidth utilization, fairness of medium access, and energy consumption. The superiority of versatile MAC against the studied benchmark protocols is established with respect to these metrics. Copyright © 2012 John Wiley & Sons, Ltd.

A schedule-based medium access control (MAC) protocol (versatile MAC (VMAC)) is proposed, analyzed, and evaluated in this paper for mobile wireless sensor networks. The performance study is conducted against time division multiple access and 802.11 with RTS/CTS by using performance metrics, namely bandwidth utilization, fairness of medium access, and energy consumption. It is shown that VMAC with a smaller value of FL compares favorably with time division multiple access and 802.11 with request to send/clear to send in terms of the aforementioned metrics when dealing with channel reuse, meaning that VMAC performs very well in short-range communication.

Space–time coded multiple-input multiple-output (MIMO) technology is an important technique that improves the performance of wireless communication systems significantly without consuming bandwidth resource. This paper first discusses the characteristics and limitations of traditional symbol-level space–time coding schemes, which work largely on the basis of an assumption that signals are sent to a block-fading channel. Therefore, the symbol-level space–time coding schemes rely on symbol-level signal processing. Taking advantage of orthogonal complementary codes, we propose a novel MIMO scheme, in this paper, based on chip-level space–time coding that is different from the traditional symbol-level space–time coding. With the help of space–time–frequency complementary coding and multicarrier modem, the proposed scheme is able to achieve multipath interference-free and multiuser interference-free communications with simple a correlator detector. The proposed chip-level space–time coded MIMO works well even in a fast fading channel in addition to its flexibility to achieve diversity and multiplexing gains simultaneously in varying channel environments. Copyright © 2012 John Wiley & Sons, Ltd.

A chip-level space–time coding (CLSTC)-based multiple input-multiple output (MIMO) system has an inherent ability to offer interference-free communication, including multipath interference (MI)-free (MI-limited performance is one of the most serious drawbacks of symbol-level S-T coding) and multi-user interference (MUI)-free (MUI is the major interference source of multiuser systems). The orthogonality among the proposed S-T codes is achieved at chip-level, and thus, a CLSTC-based MIMO system can be designed jointly with a CDMA system under a unified platform.

In this paper, we address the problem of multiple access interference (MAI) in a downlink multicarrier code division multiple access system. Because in the realistic case of correlated faded subcarriers, MAI greatly depends on the codes assigned to users, one way of improving performance without increasing receiver complexity consists in an appropriate code selection. We propose a code allocation strategy with the following properties: possible use with any code sequence and equalizer, low complexity, and efficient management of load variations. The allocation problem is formulated as a minimization problem of a cost function related to MAI. First, we provide analytical expressions for the channel frequency correlation function after maximum ratio combining, equal gain combining, and minimum mean square error equalization and for the MAI power. Then, by approximating these expressions, we define a simple cost function and build an iterative algorithm on the basis of the minimum maximum criterion to select the spreading codes. Finally, a complete analysis of the allocation efficiency is provided versus key parameters, in particular, the degree of correlation between the faded subcarriers, the system load, and the equalization techniques. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we propose a spreading code allocation strategy for a downlink multicarrier code division multiple access system transmitting through a realistic correlated Rayleigh fading channel. The allocation problem is formulated as the minimization problem of a cost function based on the approximate expression of the multiple access interference power. The allocation algorithm is iterative and uses the minimum maximum criterion to select the spreading codes of the active users. Via simulation results, we provide a complete analysis of the code allocation efficiency.

Because of the very low signal duty cycles, synchronization is the most critical issue in ultra wideband (UWB) impulse radio (IR) systems. Some effective synchronization schemes like a symbol-differential (SD) IR-UWB receiver have been proposed to synchronize received signals rapidly. Yet, SD IR-UWB receiver is unsuitable for operation in multi-user environment because of multiple access interference (MAI). By taking advantage of frame-differential IR-UWB receivers, we propose a parallel frame-differential (PFD) IR-UWB receiver to do so. Our proposed PFD IR-UWB receiver manifests better immunity against message passing interface and MAI than the SD IR-UWB. Based on this PFD IR-UWB receiver, uncertain (search) regions are limited to one frame duration without any symbol-level synchronization process. Performance of PFD and SD receivers are compared by computer simulations, showing that the proposed PFD receiver not only achieves significant bit error rate performance but also better and more robust results than the SD receiver in this literature. Copyright © 2012 John Wiley & Sons, Ltd.

We proposed that parallel frame-differential (PFD) impulse radio-ultra wideband (IR-UWB) receiver has a better immunity against message passing interface and multiple access interference than the symbol-differential (SD) IR-UWB receiver does. Based on this PFD IR-UWB receiver, the uncertain regions are limited to one frame duration without any symbol-level synchronization process. The performance of the PFD receiver and that of the SD receiver are compared using computer simulations. The computer experiments showed that the proposed PFD receive not only can achieve significant bit error rate performance but also can obtain both better and more robust results than the SD receiver in this literature. In Figure 1, the performances of the proposed synchronization scheme and SD synchronization scheme are compared. The figures show that the proposed synchronization scheme has a better performance than the SD scheme operating in single-user environment or in multi-user environment.

In cognitive radio (CR), the single-threshold cooperative detection is sensitive to the noise power. In this paper, a double-threshold cooperative detection scheme based on weighed combination is proposed to improve the global detected performance of the cooperative detection. The double thresholds that are decided by the restriction probability are adopted to divide the energy statistics observed by CRs into three subareas, and the detected performance of the CRs locating in the confusion area is fortified through the weighed data fusion by the coordinator. The CRs in the other two areas can make local binary decisions because of their exact sensing performance and then forward their 1-bit decisions to the coordinator that will combine all the received decisions to give the final decision on the presence of the primary user. In this paper, both the periodic single-band and wideband cooperative detections are investigated, and the probabilities of spectrum utilization by these two patterns are respectively analyzed. The simulation shows that the detection probability of the proposed scheme is better than that of the single-threshold cooperative detection with decision fusion but slightly worse than that of the single-threshold cooperative detection with data fusion. However, the average number of the bits sent to the coordinator by the proposed algorithm is less than that by the data fusion, and it may increase by the decreasing of the restriction probability. The simulation also shows that the periodic wideband sensing can obtain higher spectrum utilization than the periodic single-band sensing. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, a double-threshold cooperative detection scheme based on weighed combination is proposed in order to improve the global detected performance of the cooperative detection. Double thresholds are adopted to divide the energy statistic observed by CR into three sub-areas, and the detected performance of the CRs locating in the confusion area is fortified through the weighed data fusion. Both the periodic single-channel and wideband cooperative sensing mechanisms are also investigated in this paper.

In this paper, partial feedback schemes for a multiple input multiple output orthogonal frequency division multiple access system using a random beamforming are analyzed and optimized. For partial feedback schemes, the partial channel quality indicator feedback schemes and the partial channel quality rank indicator feedback schemes are considered. For these schemes, we first derive the effective downlink spectral efficiencies by considering the required uplink resource for feedback together over block fading channels. Then, by using the analysis, the amount of feedback overhead per user is optimized to maximize the effective downlink spectral efficiency according to the system and channel parameters. From the analysis and numerical examples, we show that the partial channel quality rank indicator feedback scheme provides better performance than the partial channel quality indicator feedback scheme unless the channel rapidly varies owing to its feedback efficiency, and the proposed adaptive control of the feedback overhead can improve the performance of practical systems, such as the 3rd generation partnership project (3GPP) long term evolution, in practical scenarios. Copyright © 2012 John Wiley & Sons, Ltd.

We consider the feedback optimization problem to maximize the overall spectral efficiency in multi-user MIMO-OFDMA systems using a random beamforming with partial feedback information. From the analysis and numerical examples, we show that the partial channel quality rank indicator feedback scheme provides better performance than the partial channel quality indicator feedback scheme unless the channel rapidly varies owing to its feedback efficiency, and the proposed adaptive control of the feedback overhead can improve the performance of practical systems, such as 3GPP LTE, in practical scenarios.

In wireless sensor networks, the routing control overhead could be large because multiple relays are involved in the routing operation. In order to mitigate this problem, a promising solution is to use tier-based anycast protocols. The main shortcoming of these protocols is that they can consume a much greater amount of energy as compared with other competing protocols using deterministic routing. In this paper, we analyze, in depth, a tier-based anycast protocol and develop a new technique of improving network lifetime. Our solution is guided by our analytic framework that consists of subtiering and a new forwarding protocol called ‘scheduling controlled anycast protocol’. We formulate the problem for finding an optimal duty cycle for each tier with a delay constraint as a minimax optimization problem and find its solution, which we show is unique. From the analytical results, we find that the network lifetime can be significantly extended by allocating a different duty cycle adaptively for each tier under a delay constraint. Through simulations, we verify that our duty cycle control algorithm enhances the network lifetime by approximately 70% in comparison with an optimal homogeneous duty cycle allocation. Copyright © 2012 John Wiley & Sons, Ltd.

We develop a new analytical model that provides an efficient way to analyze the characteristics of the tier-based anycast protocol. On the basis of our analytical model, we describe an optimization problem and find an optimal homogeneous duty cycle that satisfies a delay constraint. We also propose a new protocol named the scheduling controlled anycast protocol (SCAN) which finds an optimal heterogeneous duty cycle for each tier to save more energy with a delay constraint.

We investigate the problem of precoding optimization in an amplify-and-forward multiple-input-multiple-output relay system. Most reported works on this problem focus chiefly on the design of relay precoder without simultaneously optimizing the direct link. In this paper, we propose a method for joint source/relay precoder design, taking both direct and relay links into account. Our design is based on maximizing the mutual information (MI) under limited transmission power constraints at the source and relay, respectively. We first formulate a constrained optimization problem before relaxing the original cost function for tractability and derive a MI lower bound. This elaborate bound can asymptotically approach the exact expression of MI in an iterative fashion. In contrast to previous strategies, we then prove that the optimal structure of the source and relay precoders jointly convert the multiple-input-multiple-output relay channel into a bank of single-input-single-output relay channels without having to assume a beamforming structure to simplify the derivation. Specifically, the linear precoding design problem degenerates into power loading among multiple single-input-single-output relay channels. Applying standard Lagrange technique results in a scalar convex optimization, and it can be readily solved by iterative water filling. Numerical examples demonstrate that the proposed scheme, either exploiting partial or full channel state information, significantly outperforms the existing methods. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we propose a method for joint source/relay precoder design, taking both direct and relay links into account. Our design is based on maximizing the mutual information under limited transmission power constraints at the source and relay, respectively. Numerical examples demonstrate that the proposed scheme, either exploiting partial or full channel state information, significantly outperforms the existing methods.

Intercell interference is the main issue limiting the capacity of modern orthogonal frequency-division multiple access based cellular networks. Recently, extensive research work has been carried out in this field, and intercell interference coordination techniques have been recognized as key enablers of current (and future) cellular technologies. In this article, (i) a comprehensive survey of the most representative contributions is provided together with (ii) a generic methodology to measure their actual merit. The performance of several interference avoidance strategies has been evaluated both from system and user point of view in the context of a Long Term Evolution (LTE)-based network considering not only synthetic cellular scenarios but also realistic deployments. Our literature review indicates that there is a need for adaptive/operator-customizable low-complex intercell interference coordination (ICIC) schemes suitable for realistic LTE deployments. Results obtained by means of a comprehensive set of simulations corroborate and support this premise. In this article, it is shown that simultaneous gains in terms of spectral/energy efficiency and fairness can be achieved through dynamic mechanisms with respect to both classic hard reuse schemes and static ICIC techniques. Besides numerical results, a novel merit assessment methodology based on several weighted performance metrics is proposed. Our findings show that dynamic schemes outperform static techniques by around 20–35% in realistic deployments. Copyright © 2012 John Wiley & Sons, Ltd.

Intercell interference coordination is without a doubt one of the main enablers of modern cellular system. In this article, the performance of such techniques in the context of realistic Long Term Evolution-based deployments is investigated. Results indicate that by means of dynamic coordination, significant gains can be achieved, and hence, the need for low-complex and feasible solutions is identified as a promising research topic.

Network coding provides a powerful mechanism for improving performance of wireless networks. In this paper, we present an analytical approach for end-to-end delay analysis in wireless networks that employs inter-session network coding. Prior work on performance analysis in wireless network coding mainly focuses on the throughput of the overall network. Our approach aims to analyze the delay of each flow in the network. The theoretical basis of our approach is network calculus. In order to use network calculus to analyze the performance of traffic flows in the network, we have to address three specific problems: identifying traffic flows, characterizing broadcast links, and measuring coding opportunities. We propose solutions for these problems and discuss the practical issues when applying the approach in practice. We make three main contributions. First, we obtain theoretical formulations for computing the queueing delay bounds of traffic flows in wireless networks with network coding. Second, with the formulations, we figure out the factors that affect the queueing delay of a flow and find that first-in first-out scheduling cannot fully exploit the benefit of network coding. Third, in order to exploit our findings, we introduce a new scheduling scheme that can improve the performance of current practical wireless network coding. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we analyze the end-to-end delay of each flow in wireless networks that employ inter-session network coding. On the basis of the theory of network calculus, we derive formulations for the delay in estimating and figure out factors that affect the delay. With the understanding of the delay in wireless network coding, we introduce a new scheduling scheme to improve the network performance.

In this paper, we propose a quality of service (QoS)-sensitive energy efficiency optimization mechanism for 802.11 networks on the basis of the dynamic and simultaneous adjustment of the content window (W) and retry attempts limit (r) of the media access control (MAC) sublayer. The use of both operational variables let us not only find the optimum operational point regarding energy efficiency but also attain a positive impact on the QoS, which improves the results obtained with current single-variable optimization strategies. The model under consideration includes external noise and does not impose the saturation condition in stations and as such is well suited for real-time industrial applications under noisy channels. Results obtained from simulation confirm the advantages of adjusting simultaneously W and r versus adjusting either one separately, obtaining a slight improvement in energy efficiency and resulting in less loss and delay at the MAC sublayer. Copyright © 2012 John Wiley & Sons, Ltd.

We propose the join optimization of both 802.11 MAC parameters content window (W) and retry limit (r) in order to simultaneously maximize the energy efficiency and minimize the delay or loss. Results for uplink constant bit rate traffic show a significant improvement respect to state of art.

Multi-input multi-output orthogonal frequency-division multiplexing (MIMO-OFDM) has been actively studied for high data rate communications over the bandwidth-limited underwater acoustic (UWA) channels. Unlike existing receivers that treat the intercarrier interference (ICI) as additive noise, in this paper, the proposed receiver considers ICI explicitly together with the co-channel interference (CCI) due to parallel transmissions in MIMO-OFDM. Using a recently developed progressive receiver framework, the proposed receiver starts with low-complexity ICI-ignorant processing and then progresses to ICI-aware processing with increasing ICI levels. The key components of the proposed receiver include the following: (1) compressed sensing-based sparse channel estimation, (2) soft-input soft-output minimum mean square error/Markov chain Monte Carlo detector for interference mitigation, and (3) soft nonbinary low-density parity check decoding. In addition to simulation, we use real data from the Surface Processes and Acoustic Communications Experiment 2008 (SPACE08) and the Mobile Acoustic Communications Experiment 2010 (MACE10) to verify the system performance, where the transmitter in SPACE08 was stationary and that in MACE10 was slowly moving. Simulation and experimental results show that explicitly addressing ICI and CCI significantly improves the performance of MIMO-OFDM in UWA systems. Copyright © 2012 John Wiley & Sons, Ltd.

A practical receiver to mitigate the intercarrier interference (ICI) and co-channel interference (CCI) jointly for underwater acoustic MIMO-OFDM systems is investigated. The proposed receiver adopted a progressive framework, which starts from a simple ICI-ignorant channel model and then progresses to an ICI-aware model to explicitly deal with the ICI together with CCI. This way, the receiver can self-adapt its model complexity towards the unknown severity of the channel conditions.

This paper addresses target tracking in wireless sensor networks where the nonlinear observed system is assumed to progress according to a probabilistic state space model. Thus, we propose to improve the use of the quantized variational filtering by jointly selecting the optimal candidate sensor that participates in target localization and its best communication path to the cluster head. In the current work, firstly, we select the optimal sensor in order to provide the required data of the target and to balance the energy dissipation in the wireless sensor networks. This selection is also based on the local cluster node density and their transmission power. Secondly, we select the best communication path that achieves the highest signal-to-noise ratio at the cluster head; then, we estimate the target position using quantized variational filtering algorithm. The best communication path is designed to reduce the communication cost, which leads to a significant reduction of energy consumption and an accurate target tracking. The optimal sensor selection is based on mutual information maximization under energy constraints, which is computed by using the target position predictive distribution provided by the quantized variational filtering algorithm. The simulation results show that the proposed method outperforms the quantized variational filtering under sensing range constraint, binary variational filtering, and the centralized quantized particle filtering. Copyright © 2012 John Wiley & Sons, Ltd.

We propose to improve the use of the quantized variational filtering by jointly selecting the optimal candidate sensor that participates in target localization and its best communication path to the cluster head. In the current work, firstly, we select the optimal sensor in order to provide the required data of the target and to balance the energy dissipation in the wireless sensor networks. Secondly, we select the best communication path that achieves the highest signal-to-noise ratio at the cluster head; then, we estimate the target position using quantized variational filtering algorithm.

Next generation mobile networks will provide seamless mobility between existing cellular systems and other wireless access technologies. To realize a seamless vertical handover (inter-radio access technology handover) among these different access technologies, a multi-interfaced mobile station (i.e., multihomed) is a good approach to provide better handover performance in terms of packet loss rate and handover latency. In this article, we propose a novel layer 2 multihoming approach for inter-radio access technology handover between Universal Mobile Telecommunications System (UMTS) and Worldwide Interoperability for Microwave Access (WiMAX) in both integrated and tight coupling architectures. This layer 2 multihoming approach has the ability of enabling either soft handover or make-before-break handover to adapt to mobility scenarios for the sake of a lossless and short latency handover procedure. Our simulation results show that, in case of handover from UMTS to WiMAX for transmission control protocol (TCP) traffics, the layer 2 multihoming approach can achieve a lossless and zero latency handover procedure by enabling soft handover. In case of handover from WiMAX to UMTS, because of the fact that the performance gain of soft handover is more affected by the differences of bandwidth and transmission delay between these wireless links, the make-before-break handover is preferred to achieve lossless and short latency handover procedure. Copyright © 2012 John Wiley & Sons, Ltd.

The layer 2 multihoming scheme can be used to achieve a lossless and zero-latency handover procedure when handover is from low speed UMTS network to high speed WiMAX network. For handover from high speed WiMAX network to low speed UMTS network, layer 2 multihoming scheme eliminates packet losses and reduces handover latency in comparison with hard handover.

In this paper, we study the performance limit of a wireless communication system over a fading channel. The system under study consists of 1) a finite-buffer discrete-time queueing system on the link layer; and 2) a rate-adaptive channel coding system on the physical layer. The objective of this paper is to analyze the relationship among data rate (R), packet error probability (E), and delay bound (D) under the interaction between the link layer and the physical layer. In our analysis, we consider three types of packet errors; that is, 1) packet drop due to full buffer; 2) packet drop due to delay bound violation; and 3) packet decoding error due to channel noise. We obtain an upper bound on the packet error probability. Furthermore, by minimizing the packet error probability over the transmission rate, we obtain an optimal rate control policy that guarantees the user-specified data rate and delay bound. In the case of constant arrival, the optimal rate control policy results in a rate-error-delay triplet; then, by varying data rate and delay bound, we obtain rate-error-delay Pareto-optimal surface, which serves as the performance limit of the system under study. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we study the performance limit of a wireless communication system over a fading channel. We obtain an upper bound on the packet error probability. Furthermore, by minimizing the packet error probability over the transmission rate, we obtain an optimal rate control policy that guarantees the user-specified data rate and delay bound.

In wireless sensor networks, continued operation of battery-powered devices plays a crucial role particularly in remote deployment. The lifetime of a wireless sensor is primarily dependent upon battery capacity and energy efficiency. In this paper, reduction of the energy consumption of heterogeneous devices with different power and range characteristics is introduced in the context of duty scheduling, dynamic adjustment of transmission ranges, and the effects of IEEE 802.15.4-based data aggregation routing. Energy consumption in cluster-based networks is modeled as a mixed-integer linear and nonlinear programming problem, an NP-hard problem. The objective function provides a basis by which total energy consumption is reduced. Heuristics are proposed for cluster construction (Average Energy Consumption and the Maximum Number of Source Nodes) and data aggregation routing (Cluster-based Data Aggregation Routing) such that total energy consumption is minimized. The simulation results demonstrate the effectiveness of balancing cluster size with dynamic transmission range. The heuristics outperform other modified existing algorithms by an average of 15.65% for cluster head assignment, by an average of 22.1% for duty cycle scheduling, and by up to 18.6% for data aggregation routing heuristics. A comparison of dynamic and fixed transmission ranges for IEEE 802.15.4-based wireless sensor networks is also provided. Copyright © 2012 John Wiley & Sons, Ltd.

The main purpose of the proposed Cluster-based Data Aggregation Routing was to aggregate the data close to the source nodes and routing sequential. The number of packets that travel in the network was reduced when two or more packets were aggregated early to decrease energy consumption. The operations are as follows: (i) the initialized pseudo-destination connects to a sink node, (ii) the remainder source nodes reach the destination via a close routed node, and (iii) the pseudo-source is used to find the shortest path to pseudo-destination firstly.

Modeling of wireless channels, especially non-stationary fading channels, is important for design and performance analysis of wireless communication systems. Recently, we proposed a new approach to modeling non-stationary fading channels, based on the theory of evolutionary spectrum (ES). In this paper, we develop a time-varying autoregressive (AR) model for a non-stationary flat fading channel; specifically, we develop a method to determine the time-varying coefficients of the AR channel model, given the ES of a non-stationary process. Furthermore, with the ES theory, we develop a trace-driven time-varying AR channel simulator to generate a non-stationary flat fading process. Simulation results show that the ES of the channel gain process produced by our joint ES-and-AR-based channel model agrees well with the user-specified ES, indicating the accuracy of our joint ES-and-AR-based channel model. Copyright © 2012 John Wiley & Sons, Ltd.

Recently, we proposed a new approach to modeling non-stationary fading channels, based on the theory of evolutionary spectrum (ES). In this paper, we develop a time-varying autoregressive (AR) model for a non-stationary flat fading channel; specifically, we develop a method to determine the time-varying coefficients of the AR channel model, given the ES of a non-stationary process. Furthermore, with the ES theory, we develop a trace-driven time-varying AR channel simulator to generate a non-stationary flat fading process. Simulation results show that the ES of the channel gain process produced by our joint ES-and-AR-based channel model agrees well with the user-specified ES, indicating the accuracy of our joint ES-and-AR-based channel model.

In this paper, we propose several frequency reuse coordination schemes for interference management in orthogonal frequency division multiple access. The aim of these schemes, working together with time and frequency domain packet scheduling, is to achieve reuse of 1 at sector level in a tri-sectorized base station scenario. Inter-sector interference is strong at the frontier between sectors, and a tight coordination scheme needs be applied. To support this coordination scheme, the users' location information is then essential to determine if a user is prone to suffer strong inter-sector interference. The performance of these resource allocation algorithms is compared with schemes based on fractional frequency reuse, where reuse of 1 at cell level is assumed. Copyright © 2012 John Wiley & Sons, Ltd.

This paper proposes several frequency reuse coordination schemes for interference management in orthogonal frequency division multiple access systems. Working together with time and frequency domain packet scheduling, the aim is to achieve reuse of 1 at sector level in a tri-sectorized base station scenario. Inter-sector interference is strong at the frontier between sectors, and a tight coordination scheme needs be applied. To support this coordination scheme, users' location information is then essential to determine if a user is prone to suffer strong inter-sector interference.

In the broadband era, narrowband short message service (SMS) is still the most popular wireless data service. Many studies have been conducted to investigate the performance of SMS based on the arrival rates of short messages. From Chunghwa Telecom's commercial SMS call data records, we observed that even if the SMS arrival rates are the same, the distributions for the number of SMS arrivals per half hour are quite different for various observed days. We further identify that for the SMS traffic in a specific day, there are non-burst and burst periods. This paper investigates the SMS behaviors on weekdays, weekends, and holidays (specifically, new years' days and eves). With the assistance of kernel-based fitting method, we derive the SMS arrival number distributions of various traffic types and observed days. Our approach fits each SMS arrival number distribution by three cubic polynomial functions that can accurately capture the SMS behaviors. On the basis of the SMS arrival number distributions derived from our model, the mobile operators have better understanding about the volumes of short messages in different times and days, which can be used to design more flexible short message charging rates. Copyright © 2012 John Wiley & Sons, Ltd.

This paper derives the short message service (SMS) arrival number distributions of various traffic types and observed days. Our approach fits each SMS arrival number distribution by three cubic polynomial functions that can accurately capture the SMS behaviors. On the basis of the SMS arrival number distributions derived from our model, the mobile operators have better understanding about the volumes of short messages in different times and days, which can be used to design more flexible short message charging rates.

In this paper, we propose a new diversity combining scheme to save power, which is called as the generalized selection combining with double threshold (DT-GSC). It selects the branch whose SNR is above an input threshold to combine, and this process will keep running until the combined output SNR is larger than an output threshold or until all paths are examined. The values of both thresholds are required to be predetermined on the basis of the practical communication conditions. For comparing the complexity of various combining schemes, we will show the mathematical formulas of the average number of path estimation and the average number of combined branches. Moreover, we will also compare the average bit-error-ratio performance of the proposed DT-GSC with absolute threshold GSC (AT-GSC) and output threshold MRC (OT-MRC). Numerical examples and simulation results show that the proposed DT-GSC leads to a lower complexity than the conventional AT-GSC and OT-MRC while it has a satisfactory performance.Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we propose a new diversity combining scheme to save the power consumption, DT-GSC. It selects the branch whose SNR is above an input-threshold to combine, and this process will keep running until the combined output SNR is larger than an output-threshold or all paths are examined. Numerical examples and simulation results show that the proposed DT-GSC leads to a lower complexity than the conventional AT-GSC and OT-MRC while it has a satisfactory performance.

Emerging wireless sensor/actuator network (WSAN) technology has the potential to enable semi-autonomous airflow control to improve the aerodynamic performance of aircraft. In this paper, a WSAN comprising of multiple linear sensor clusters terminated by actuators is proposed for active airflow control with the objective of minimizing convergecast latency. Here, the convergecast delay is defined as the time required from the beginning of a sampling period to all all sensor's data of this sampling period is received by the actuator. The objective is achieved by minimizing the separation distance of concurrent data transmission so that the number of nodes sending data in the same time slot is maximized. The problem turns into a scheduling problem with a proper selection of interference separation. However, most existing work on the scheduling in linear networks use the minimum separation of two hops to avoid collisions. This paper examines the relationship between the hop separation, signal-to-noise ratio, and the latency to make a selection of interference separation. A new interference aware hybrid line scheduling (HLS) algorithm is proposed and its energy consumption is analyzed. Compared with other line scheduling policies, the analysis and simulation results show that, at moderately high node densities, the proposed HLS with carefully selected hop separation is able to reduce both the delay by up to 15% and the energy consumption somehow. Copyright © 2012 John Wiley & Sons, Ltd.

A new interference aware hybrid line scheduling (HLS) algorithm is proposed for wireless sensor actuator networks in aeroplane active airflow control. Its energy consumption is analyzed and compared with other convergecast scheduling policies. The analysis and simulation results show that, at moderately high node densities, the proposed HLS with carefully selected hop separation is able to reduce both the delay by up to 15% and the energy consumption somehow.

Distance estimation is vital for localization and many other applications in wireless sensor networks. In this paper, we develop a method that employs a maximum-likelihood estimator to estimate distances between a pair of neighboring nodes in a static wireless sensor network using their local connectivity information, namely the numbers of their common and non-common one-hop neighbors. We present the distance estimation method under a generic channel model, including the unit disk (communication) model and the more realistic log-normal (shadowing) model as special cases. Under the log-normal model, we investigate the impact of the log-normal model uncertainty; we numerically evaluate the bias and standard deviation associated with our method, which show that for long distances our method outperforms the method based on received signal strength; and we provide a Cramér–Rao lower bound analysis for the problem of estimating distances via connectivity and derive helpful guidelines for implementing our method. Finally, on implementing the proposed method on the basis of measurement data from a realistic environment and applying it in connectivity-based sensor localization, the advantages of the proposed method are confirmed. Copyright © 2012 John Wiley & Sons, Ltd.

Distance estimation is vital for localization and many other applications in wireless sensor networks. This paper presents a method that employs a maximum-likelihood estimator to estimate distances between a pair of neighboring nodes by using their local connectivity information. By a Cramer-Rao lower bound analysis, extensive simulations and practical experiments, the advantages of the proposed method are confirmed.

The invention of cognitive radio (CR) concept aims to overcome the spectral scarcity issues of emerging radio systems by exploiting under-utilization of licensed spectrum. Determining how to allocate unused frequency bands among CR is one of the most important problems in CR networks. Because different CRs may have different quality-of-service requirements, they may have different objectives. In voice communication, high-speed transmission is the most important factor; hence, voice radios always try to maximize their transmission rate. However, in data communication, the most important factor is the bit error rate. The data radios always try to maximize their signal-to-interference-plus-noise ratio (SINR). In this paper, two non-cooperative games named interference minimization game and capacity maximization game, which reflect the target of data radios and voice radios, respectively, are proposed. From the simulations, after these games are applied, the average SINRs of all players at each channel are improved. The average SINR of players in each channel after applying the capacity maximization game is smaller than that after applying the interference minimization game. However, in comparison with that after applying the interference minimization game, the average capacity of players after applying capacity maximization approach is larger. Copyright © 2012 John Wiley & Sons, Ltd.

Two different non-cooperative games named interference minimization game and capacity maximization game, which reflect the target of data radios and voice radios, respectively, are proposed in this paper to jointly allocate power and spectrum among cognitive radios in cognitive radio networks.

In this paper, we propose to provide throughput guarantees in heterogeneous wireless mesh networks by jointly optimizing routing and Medium Access Control configuration. Our solution is based on the notion of linearized capacity region, which provides a technology-independent way of representing the capacity of a wireless link (thereby hiding the technology specifics to the upper layers). From the available capacity of the underlying links as given by the linearized capacity region, we propose two routing algorithms (based on multipath and single path) that find optimal paths for all the flows in the network given their throughput requirements. The throughput allocation resulting from routing is then provided to each link, which uses this information to optimize its technology-specific Medium Access Control parameters. The proposed approach is evaluated in a heterogeneous scenario comprising Wireless Local Area Networks (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) technologies and is shown to outperform previous solutions by (at least) a factor of 2.Copyright © 2012 John Wiley & Sons, Ltd.

This paper proposes to provide throughput guarantees in heterogeneous wireless mesh networks by jointly optimizing routing and Medium Access Control configuration. Our solution is based on the notion of linearized capacity region, which provides a technology-independent way of representing the capacity of a wireless link.

Medium Access Control is an important component in cognitive radio that allow secondary users to identify and access spectrum opportunity without interfering with primary users. In this paper, a queueing model to analyze the performances of the secondary users in a cognitive radio network is presented. The queueing model considers the transmissions of a secondary system where a Medium Access Control algorithm is used to enable the secondary users to sense and access the channels. Also, a simple scheduler is employed to assign transmission time slots to the secondary users. Because the value of the system parameters can be perturbed and cannot be determined precisely, the analysis is extended to take uncertainty into account. In this case, a robust optimization method to study the Markov chain with uncertainty is applied to obtain the stationary probabilities of the queueing model under uncertainty. The lower and upper bounds of performance measures are obtained and compared with the nominal value. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we have studied the D-norm uncertainty and its impact on the performance measures in a cognitive radio network. Using the approach of Markov chain with uncertainty, we have analyzed the lower and upper bound performances (i.e., mean number of packets in queue, packet dropping probability, queue throughput, and average delay) of a secondary user in a cognitive radio network. These lower and upper bounds can be used to investigate the cognitive radio network in the worst-case and best-case scenarios, which will be useful for the design of radio resource management for secondary users.

Power allocation is an important issue for spectrum sharing of unlicensed bands, in which multiple unlicensed systems may coexist and operate. Some recent works have been reported on spectrum sharing in frequency-flat (FF) unlicensed bands. However, there has not been much work on power allocation for spectrum sharing in frequency-selective (FS) unlicensed bands. For multiple cooperative systems cooperating on FS interference channels (ICs), we study an optimal power allocation strategy, which allows the transmission power density to vary within one subcarrier. By showing the duality of FS and parallel FF channels, we can therefore compute the achievable rate region of the proposed strategy when systems cooperate with each other. For non-cooperative scenarios, we construct a game-theoretical framework for multiple selfish systems on FS ICs. This framework enables us to utilize existing protocols designed for FF ICs to FS scenarios. By numerical results, in both cooperative and non-cooperative scenarios, we show that the proposed strategy achieves a larger rate region than a conventional strategy, where the transmission power density on each subcarrier is set equal. Our work can be regarded as an extension of previous works for FF scenarios. Copyright © 2012 John Wiley & Sons, Ltd.

For multiple systems cooperating on frequency-selective (FS) interference channels (ICs), we study an optimal power allocation strategy, which allows transmission power density to vary within one subcarrier. By showing the duality of FS and the parallel frequency-flat (FF) channels, we compute the achievable rate region of the proposed strategy when systems cooperate with each other. For multiple selfish systems on FS ICs, we construct a game-theoretic framework that enables us to apply existing protocols designed for frequency-flat ICs to FS scenarios.

In this paper, we consider the reliable broadcast and multicast lifetime maximization problems in energy-constrained wireless ad hoc networks, such as wireless sensor networks for environment monitoring and wireless ad hoc networks consisting of laptops or PDAs with limited battery capacities. In packet loss-free networks, the optimal solution of lifetime maximization problem can be easily obtained by tree-based algorithms. In unreliable networks, we formulate them as min–max tree problems and prove them NP-complete by a reduction from a well-known minimum degree spanning tree problem. A link quality-aware heuristic algorithm called Maximum Lifetime Reliable Broadcast Tree (MLRBT) is proposed to build a broadcast tree that maximizes the network lifetime. The reliable multicast lifetime maximization problem can be solved as well by pruning the broadcast tree produced by the MLRBT algorithm. The time complexity analysis of both algorithms is also provided. Simulation results show that the proposed algorithms can significantly increase the network lifetime compared with the traditional algorithms under various distributions of error probability on lossy wireless links. Copyright © 2012 John Wiley & Sons, Ltd.

We consider the reliable broadcast and multicast lifetime maximization problems in energy-constrained wireless ad hoc networks with lossy channels. We formulate them as min–max tree problems and prove them NP-complete. A link quality-aware heuristic algorithm is then proposed to build a multicast tree that maximizes the network lifetime. Simulation results show that the proposed algorithm can significantly increase the network lifetime compared with the traditional algorithms under various distributions of error probability on lossy wireless links.

Energy efficiency in specific clustering protocols is highly desired in wireless sensor networks. Most existing clustering protocols periodically form clusters and statically assign cluster heads (CHs) and thus are not energy efficient. Every non-CH node of these protocols sends data to the CH in every time slot of a frame allocated to them using the time division multiple access scheme, which is an energy-consuming process. Moreover, these protocols do not provide any fault tolerance mechanism. Considering these limitations, we have proposed an efficient fault-tolerant and energy-efficient clustering protocol for a wireless sensor network. The performance of the proposed protocol was tested by means of a simulation and compared against the low energy adaptive clustering hierarchy and dynamic static clustering protocols. Simulation results showed that the fault-tolerant and energy-efficient clustering protocol has better performance than both the low energy adaptive clustering hierarchy and dynamic static clustering protocols in terms of energy efficiency and reliability. Copyright © 2012 John Wiley & Sons, Ltd.

Achieving energy efficiency and reliability in clustering protocols is highly desired in wireless sensor networks. Although most existing clustering protocols focus on achieving energy efficiency, they are not fault tolerant. Hence, we propose an efficient fault-tolerant and energy-efficient clustering protocol for a wireless sensor network, which outperforms both the low energy adaptive clustering hierarchy and dynamic static clustering protocols in terms of network energy consumption and lifetime.

In this paper, performance of joint transmit and receive antenna selection in each hop of dual hop amplify-and-forward relay network is analyzed over flat and asymmetric Nakagami-m fading channels. In the network, source, relay, and destination are equipped with multiple antennas. By considering relay location, we derive exact closed-form cumulative distribution function, moment generating function, moments of end-to-end signal-to-noise ratio and closed form symbol error probability expressions for fixed and channel state information-based relay gains. We also derive the asymptotical outage probability and symbol error probability expressions to obtain diversity order and array gain of the network. Analytical results are validated by the Monte Carlo simulations. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, performance of joint transmit and receive antenna selection in each hop of dual hop amplify-and-forward relay network is analyzed over flat and asymmetric Nakagami-m fading channels. By considering relay location, we derive exact closed-form cumulative distribution function, moment generating function, moments of end-to-end signal-to-noise ratio, and closed form symbol error probability expressions for fixed and channel state information-based relay gains. We also derive the asymptotical outage probability and symbol error probability to obtain diversity order and array gain of the network.

We develop an efficient hard detector for multiple-input multiple-output (MIMO) channels, which adaptively combines maximum-likelihood detection (MLD) and minimum-mean-square error with a successive interference canceler together. Unlike the conventional joint combination scheme, which may suffer from considerable degradation in bit-error-rate (BER) performance over correlated channels and where only one data stream is detected by MLD, our proposed scheme adaptively controls the number of data streams to be detected by MLD based on an analytical characterization of reliability for the detection. Simulation results illustrate that near-optimal BER performance can be obtained at much lower computational complexity by the proposed method as compared with existing techniques, regardless of the spatial correlation of the MIMO channels. Copyright © 2012 John Wiley & Sons, Ltd.

An adaptive combination of maximum-likelihood detection and a minimum-mean-square error with successive interference canceler is proposed for spatially correlated multiple-input multiple output channels. It adaptively controls the number of data streams to be detected by maximum-likelihood detection based on an analytical characterization of reliability for the detection.

The unused time slots in a primary time division multiple access (TDMA) network are regarded as the potential channel access opportunities for secondary users (SUs) in cognitive radio (CR). In this paper, we investigate the medium access control protocols that enable SUs to access a common TDMA channel with primary users (PUs). The primary traffic is assumed to follow a Bernoulli random process. A two-state Markov chain is used to model the secondary traffic, and two different scenarios are considered. The first scenario assumes that the secondary packet arrivals are independent and follow a Bernoulli random process and a cognitive carrier sensing multiple access (Cog-CSMA) protocol is proposed. A Rayleigh fading channel is considered in evaluating Cog-CSMA, and its throughput expression is derived in this paper. The second scenario assumes that the packet arrivals follow a correlated packet arrival process and a cognitive packet reservation multiple access (Cog-PRMA) protocol is proposed. A Markov chain is used to model the different system states in Cog-PRMA and derive the throughput. Numerical results show that the Cog-CSMA and Cog-PRMA protocols achieve the objective of supporting secondary transmissions in a TDMA network without interfering the PUs' transmissions and improve the network bandwidth utilization.Copyright © 2012 John Wiley & Sons, Ltd.

The idle time slots in a time division multiple access (TDMA) network are regarded as spectrum holes in cognitive radio. Cognitive carrier sensing multiple access and cognitive packet reservation multiple access are proposed for secondary users to share a common TDMA channel with the primary users.

In social groups, complex group behavior often emerges from the local interaction among simple individuals. Throughout this study, we assume that individuals can access information by way of wireless communication. In this case, individuals are able to exchange accurate information with each other as long as wireless communication links between them are allowed. Subsequently, we propose a consensus decision-making model for studying the consistency of group behavior considering both the wireless communication range and the probability of successful communication. Our simulation results show the following conclusions: (i) consistency of the group behavior is absolutely achieved, when the wireless communication range is large enough and the probability of successful communication p = 1; (ii) when the wireless communication range is large enough, the consistency of the group behavior is still achieved as long as p is bigger than some small constant; and (iii) the law in (iii) remains applicable when the number of individuals in the group changes. Therefore, one may infer that consistency of group behavior in mobile sensors is much more related to the extent of distribution of obtainable information than the amount of information, where the extent of distribution of obtainable information means that each individual can obtain information from wider area or from those individuals who are not only in its local area. Copyright © 2012 John Wiley & Sons, Ltd.

Individuals are able to exchange accurate information with each other as long as wireless communication links between them are allowed. Subsequently, we propose a consensus decision-making model for studying the consistency of group behavior considering both the wireless communication range and the probability of successful communication.

Reliability and timeliness are two critical requirements of vehicle safety-related communication services in VANETs. In this paper, we develop an analytical model to analyze the packet reception rate and end-to-end delay of emergency message delivery operation in a VANET environment when multihop broadcast communications are used. The model is applied to derive closed-form expressions of the end-to-end delay of two popular multihop message propagation methods, that is, the farthest-distance method and the counter-based method. Extensive simulations are conducted to validate the correctness of the theoretic results and compare the performance of the two message propagation methods. Observations are provided for the design of efficient and robust emergency message propagation methods for vehicular wireless communication networks. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we develop an analytical model to analyze the packet reception rate and end-to-end delay of emergency message delivery operation in a VANET environment when multihop broadcast communications are used. The model is applied to derive closed-form expressions of the end-to-end delay of two popular multihop message propagation methods, that is, the farthest-distance method and the counter-based method. Results demonstrate how communication network conditions affect the end-to-end delay performance of multihop broadcast schemes in VANETs

The deployment of multicarrier code division multiple access as the transmission scheme of the spectrum overlay based cognitive radio (CR) networks faces two challenging issues: (i) the need for spreading codes with arbitrary length and (ii) the interfering effect of the leaked power (due to spectral sidelobes) to the adjacent spectral band used by the primary system. To meet these challenges, we propose two novel complex spreading code sets. For this purpose, a cost function is defined as the ratio of the power leaked to the adjacent primary band to the power transmitted to the band allowed for CR operation. The cost function is shown to be convertible to a trace ratio problem. The two complex spreading code sets are determined by deploying two different standard solutions. The first is the conventional but approximate solution based on generalized eigenvalue decomposition (GEVD) method, and the other is an iterative algorithm that converges to the optimal solution and hence outperforms the GEVD based solution. Simulation results show that by a slight decrease in number of users, the code set yielded by iterative algorithm suppresses the leaked power to almost zero. The applicability of the proposed code sets in different scenarios is discussed. Copyright © 2012 John Wiley & Sons, Ltd.

The interfering effect of the leaked power (due to spectral sidelobes) of the multicarrier techniques is a challenging issue ahead of implementation of the multicarrier based overlay cognitive radio networks. In this paper, two novel spreading codes are designed for multicarrier code division multiple access based cognitive radio networks that are determined by deploying two different solutions to an objective function in the form of a trace ratio problem. Simulation results show that by a slight decrease in the number of users, the spreading code sets suppress the leaked power to almost zero.

The demand for higher data rate has spurred the adoption of multiple-input multiple-output (MIMO) transmission techniques in IEEE 802.11 products. MIMO techniques provide an additional spatial dimension that can significantly increase the channel capacity. A number of multiuser MIMO system have been proposed, where the multiple antenna at the physical layer are employed for multiuser access, allowing multiple users to share the same bandwidth. As these MIMO physical layer technologies further evolve, the usable bandwidth per application increases; hence, the average service time per application decreases. However, in the IEEE 802.11 distributed coordination function-based systems, a considerable amount of bandwidth is wasted during the medium access and coordination process. Therefore, as the usable bandwidth is enhanced using MIMO technology, the bandwidth wastage of medium access and coordination becomes a significant performance bottleneck. Hence, there is a fundamental need for bandwidth sharing schemes at the medium access control (MAC) layer where multiple connections can concurrently use the increased bandwidth provided by the physical layer MIMO technologies. In this paper, we propose the MIMO-aware rate splitting (MRS) MAC protocol and examine its behavior under different scenarios. MRS is a distributed MAC protocol where nodes locally cooperate with one another to share bandwidth via splitting the spatial channels of MIMO systems. Simulation results of MRS protocol are obtained and compared with those of IEEE 802.11n protocol. We show that our proposed MRS scheme can significantly outperform the IEEE 802.11n in medium access delay and throughput. Copyright © 2012 John Wiley & Sons, Ltd.

Multiple-input multiple-output (MIMO) techniques significantly increase channel capacity or bandwidth. However, in the IEEE 802.11 distributed coordination function-based systems, considerable amount of bandwidth is wasted during the medium access and coordination process. In this paper, we propose the MIMO-aware rate splitting(MRS) medium access control(MAC) protocol, which allows nodes to locally cooperate and share MIMO bandwidth via splitting the spatial channels. Simulation results of MRS protocol show that the scheme outperforms the IEEE 802.11n in medium access delay and throughput.

We address the problem of subchannel and transmission power allocation in orthogonal frequency division multiple access relay networks with an aim to maximize the sum rate and maintain proportional rate fairness among users. Because the formulated problem is a mixed-integer nonlinear optimization problem with an extremely high computational complexity, we propose a low-complexity suboptimal algorithm, which is a two-step separated subchannel and power allocation algorithm. In the first step, subchannels are allocated to each user, whereas in the second step, the optimal power allocation is carried out on the basis of the given subchannel allocation and the nonlinear interval Gauss–Seidel method. Simulation results have demonstrated that the proposed algorithm can achieve a good trade-off between the efficiency and the fairness compared with two other existing relevant algorithms. In particular, the proposed algorithm can always achieve 100% fairness under various conditions. Copyright © 2012 John Wiley & Sons, Ltd.

We address the problem of subchannel and transmission power allocation in orthogonal frequency division multiple access relay networks with an aim to maximize the sum rate and maintain proportional rate fairness among users. We propose a low-complexity suboptimal algorithm, which is a two-step separated subchannel and power allocation algorithm. Simulation results have demonstrated that the proposed algorithm can achieve a good trade-off between the efficiency and the fairness compared with two other existing relevant algorithms.

The IEEE 802.16-based WiMAX technology has great potential for the fourth-generation mobile networks. Some of its service classes use the contention-based broadcast polling mechanism to request resources. In this paper, we investigate the performance experienced by these services when the network is unsaturated. In particular, we model each subscriber station as an M/G/1 queue where the service time is determined by the parameters of the network configuration and the binary exponential backoff contention resolution algorithm. We develop a fixed-point analysis to derive analytical expressions for network throughput and packet access delay. The accuracy of the analytical model is validated by comparing it with simulation over a wide range of operating conditions. The implications of various different parameter configurations on the performance are investigated using the analytical model. Moreover, we show that the model can be degenerated to the saturated condition. The utility of both the unsaturated and saturated models is further demonstrated by finding the optimal set of parameter values that maximize the network throughput. Copyright © 2011 John Wiley & Sons, Ltd.

We develop an analytical model to evaluate the performance of contention-based services of IEEE 802.16 networks under the unsaturated condition. The accuracy of the model is validated by extensive simulation results. With this model, we further develop an algorithm to determine the optimal values of network parameters that maximize the network throughput.

Signal-time coding (STC) is a newly proposed transmission scheme for half-duplex relay networks, which is able to achieve higher information flow rate by combining the traditional encoding/modulation mode in the signal domain with the signal pulse phase modulation in the time domain. However, most of the results for STC are only obtained under the ideal assumptions that the signal detections at physical layer are perfect and there are still a lot of fundamental problems to be explored. This paper considers the implementing issues of STC at physical layer in additive white Gaussian noise relay networks. Firstly, a performance evaluation criterion, the reliable information per symbol (RIPS), is proposed to characterize the performance of STC in noisy wireless networks. Secondly, a new construction scheme based on route ID for the codeword of STC is presented, and some structural properties of the codeword of STC are investigated. Thirdly, the error probabilities of STC in both the signal domain and the time domain are discussed. Furthermore, two implementing schemes, that is, the energy detection based STC (ED-STC) and the symbol detection based STC (SD-STC), are proposed, and their performance bounds in terms of RIPS are discussed. Numerical analyses show that both ED-STC and SD-STC outperform traditional transmission methods in terms of effective information rate even under some practical conditions. Copyright © 2011 John Wiley & Sons, Ltd.

This paper considers the implementing issues of signal-time coding (STC) at physical layer in additive white Gaussian noise relay networks. Firstly, a performance evaluation criterion, the reliable information per symbol (RIPS), is proposed to characterize the performance of STC in noisy wireless networks. Secondly, a new construction scheme based on route ID for the codeword of STC is presented, and some structural properties of the codeword of STC are investigated. Thirdly, the error probabilities of STC in both the signal domain and the time domain are discussed. Furthermore, two implementing schemes, that is, the energy detection based STC (ED-STC) and the symbol detection based STC (SD-STC), are proposed, and their performance bounds in terms of RIPS are discussed. Numerical analyses show that both ED-STC and SD-STC outperform the traditional transmission methods in terms of effective information rate even under some practical conditions.

User cooperation has evolved as a popular coding technique in wireless relay networks (WRNs). Using the neighboring nodes as relays to establish a communication between a source and a destination achieves an increase of the diversity order. The relay nodes can be seen as a distributed multi-antenna system, which can be exploited for transmit diversity by using distributed space–time block coding (STBC). In this paper, we investigate the bit error rate (BER) of multi-hop WRNs employing distributed STBC at the relay nodes. We develop the general model of WRNs using distributed STBC, and we derive the pairwise error probability and an approximation of the BER. We examine the impact of several parameters, such as distributed STBC at the relays, the number of relays, the distances between the nodes, and the channel state information available at the receivers, on the BER performance of the multi-hop WRN. The obtained results provide guidelines about the expected error performance and the design of channel estimation for these networks. Copyright © 2011 John Wiley & Sons, Ltd.

The aim of this paper is to investigate the bit error rate of multihop wireless relay networks employing distributed space-time block coding at the relay nodes. On the basis of the impact of several parameters (such as distributed space-time block coding at the relays, the number of relays, the distances between the nodes, and the channel state information available at the receivers) on the bit error rate performance of the wireless relay network, we provide guidelines about the expected error performance and the design of channel estimation for these networks.

In this work, a channel-power profile estimation for orthogonal frequency-division multiplexing systems, based on the cyclic prefix (CP), is introduced. By knowing the delay of each path, the time-dispersion information can be derived. The proposed method, considering long intersymbol interference (ISI) fading channels, requires only the coarse symbol timing information. More specifically, quasi-stationary fading channels are considered. The basic contribution is to obtain the maximum-likelihood estimation of the correlation coefficient based on the CP. Subsequently, the relationship between the correlation coefficient and the channel-tap powers is explored. With the estimate of correlation coefficient, the least-square solution of the channel-tap powers can be determined. The proposed method is suitable for both short and long ISI channels. Furthermore, the Cramér–Rao lower bound of the channel-power profile estimation is analyzed, and simulations confirm the advantages of the proposed estimator. Copyright © 2011 John Wiley & Sons, Ltd.

Channel-power profile estimation for orthogonal frequency-division multiplexing (OFDM) systems, which is based on the cyclic prefix (CP), is introduced. By knowing the delay of each path, we can derive the time dispersion information. The basic contribution is to obtain the maximum-likelihood (ML) estimation of the correlation coefficient on the basis of the CP. Subsequently, the relationship between the correlation coefficient and the channel-tap powers is explored. On the basis of the estimate of correlation coefficient, the least-square solution of the channel-tap powers can be determined.

For realizing robust target tracking with wireless sensor networks in the circumstance where the propagation parameters of the characteristic signal emitted by the target are unknown, a novel tracking algorithm under the particle filter framework is proposed. We propose a scheme to realize particle weight calculation without the prior knowledge about the propagation parameters of the target's characteristic signal. With the use of the monotonic relationship of the distance and the received signal strength, we define the signal characteristic sequence and particle distance sequence and utilize the modified sequence distance between the signal characteristic sequence and the particle distance sequence as the criterion to calculate the particle weight blindly with simple lightweight operations. Simulation results demonstrate the effectiveness of the proposed algorithm. Copyright © 2011 John Wiley & Sons, Ltd.

A novel lightweight blind particle filter was proposed to realize target tracking with resource-limited wireless sensor networks in the circumstance where the parameters of the target's character signal are unknown. We define the signal characteristic sequence and particle distance sequence and utilize the modified sequence distance between the signal characteristic sequence and particle distance sequence as the criterion to calculate the particle weight blindly with simple lightweight operations. Simulation results demonstrate the effectiveness of the proposed algorithm.