Versatile two-state land mobile satellite channel model with first application to DVB-SH analysis

Abstract

Standardization activities on Digital Video Broadcasting–Satellite services to Handheld Devices (DVB-SH) have driven the need for a consolidated Land Mobile Satellite (LMS) narrowband channel model. In the DVB-SH system, the satellite broadcasts a signal carrying multimedia services aimed directly to a variety of mobile (handheld or vehicular) and fixed terminals.

A three-state LMS channel model that describes the narrowband propagation channel in three possible shadowing states—line-of-sight conditions, moderate shadowing and deep shadowing—had been selected as a baseline for physical layer simulation of the DVB-SH waveform. This type of model, capable of generating complex time series, was originally selected, because it is the simplest model that allows the simulation of first- and second-order effects of the LMS channel in a realistic manner. The main limitations of such model are, first of all, that a classification in three states does not necessarily correspond with reality and, secondly, that the statistical parameters for each state were fixed for a given scenario and elevation angle. Those limitations may impact the selection of Physical Layer parameters of the DVB-SH standard.

A new channel model is proposed based on the original three-state model including two major modifications: a reduction in the number of states and the introduction of a versatile selection of statistical parameters describing each state. Furthermore, the state machine is governed either by Markov or by semi-Markov chains. The new-state classification does not necessarily correspond to intuitive physical definitions of the states as before (line-of-sight, shadowing) but instead to channel variations that share similar statistical characteristics. The two-states are termed for convenience, Good and Bad states, representing a range of LOS-to-moderate shadowing and moderate-to-deep shadowing, respectively. For the model parameters selection, datasets at L- and S-band have been analysed using an iterative algorithm that includes automatic data classification and parameter extraction. The proposed model is considered more suitable for the analysis of DVB-SH test cases.

This study starts with an overview of the main DVB-SH system parameters and assumptions. The original three-state model is briefly introduced; the new model is presented in detail, including simulator implementation. Finally, both models and experimental data sets are compared on a statistical basis. The performance of both models are discussed to show how effective the model is for the representation of shadowed conditions and therefore, its suitability for the analysis and optimal configuration of the physical and link layer parameters (namely physical layer interleaver size, link layer protection time, overall redundancy, etc.). Copyright © 2010 John Wiley & Sons, Ltd.