Wireless Communications and Mobile Computing

This paper studies the performance of several rival protocols performing both QoS-aware routing and admission control (AC) with the aim of providing throughput guarantees to applications in mobile ad hoc networks. The simulated shadow-fading environment highlights the ineffectiveness of previously-proposed methods of relying merely on the success of route discovery to perform AC, of existing congestion detection schemes and of careful re-admission of data sessions rather than fast re-routing after shadowing-induced link failures. Design guidelines for future protocols are proposed.

We identify three key elements that are critical for ensuring effective area coverage in Hybrid WSN: (i) determining the boundary of the target region and evaluating the area coverage, (ii) locating coverage holes and maneuvering mobile nodes to fill these voids, and (iii) maintaining the desired coverage over the entire operational lifetime of the network. We propose a comprehensive and distributed solution that addresses all of the aforementioned aspects of the area coverage, called MAPC (mobility assisted probabilistic coverage). A guiding principle in our design process has been to ensure that the MAPC can be readily implemented in real-world applications.

In this paper, we propose a new combined method of SPW (subblock phase weighting) for PAPR reduction and linearization technique for the power efficiency improvement and for the nonlinear compensation of HPA. Updated SPW method is used for the novel weighting factor multiplication of the complementary sequence characteristic and PAPR threshold technique. From the simulation results, it is confirmed that BER performance is significantly improved and out-of-band spectrum radiations are much mitigated. Also, power efficiency of HPA can be improved.

This paper proposes a Network-Initiated SimUltaneouS mobility (NISUS) mechanism to facilitate terminal mobility in Voice over 3GPP-WLAN. The NISUS is triggered at the packet data gateway in case of a handover occurrence. Then the mobility server is notified to perform a third party call control and a third party registration on behalf of the mobile host in parallel for session re-establishment. In addition the Master-Slave Determination procedures are proposed to handle the racing conditions fairly in a simultaneous mobility.

This paper proposes a new and simple solution, called Wi-Fi network Infrastructure eXtension (WiFIX), aimed at extending current Wi-Fi infrastructures. WiFIX is based on standard IEEE 802.1D bridges and a single-message protocol that is able to self-organize the network. Overhead analysis and experimental results show both the higher efficiency of the solution compared to the IEEE 802.11s draft standard and its good performance as far as data throughput, delay, and packet loss are concerned.

This paper proposes a novel Multi-Channel Power-Controlled Directional MAC protocol (MPCD-MAC) for nodes equipped with multiple network interfaces and directional antennas. This solution spreads the information on wireless medium reservation (RTS/CTS) to the largest set of neighbors, while data transfers take place directionally on separate channels to increase spatial reuse. Furthermore, power control is used to limit the interference produced over active nodes. Numerical results show that MPCD-MAC increases considerably both the total traffic accepted by the network and the fairness among competing connections.

In this paper, we propose a trellis exploration algorithm based preprocessing strategy to lower the peak-to-average power ratio (PAPR) of precoded MIMO-OFDM. Simulation results indicate that our proposed schemes show superior PAPR performance over conventional MIMO-OFDM with and without precoding. Additionally, our proposed approach better exploits frequency diversity resulting in BER performance gains in multi-path environments.

This paper examines the carrier frequency offset (CFO) estimation problem in the tile-based orthogonal frequency division multiple access (OFDMA) uplink systems. The existing solutions to this problem are either too complex to implement or not flexible in subcarrier allocation. To solve these problems, we propose a tile-structure based iterative multi-CFO estimation technique, which achieves high estimation accuracy, fast convergence, low complexity and is suitable for any subcarrier assignment schemes.

A Stackelberg game is applied to solve the problem of stimulating cooperation and resource allocation in cooperative transmission networks. The problem is formulated as a sellers' market competition where a relay is willing to share its resource with multiple users. And a distributed algorithm is performed to search the Nash equilibrium, i.e., the solution of the game, with the convergence conditions of the algorithm being analyzed.