Space-time receivers for GSM radio interfaces in subway tunnel environments

In this paper, we investigate how to increase the capacity of GSM (Global System for Mobile communications) radio interfaces in subway tunnel environments by means of antenna arrays and Space–Time (ST) receivers. We address the modeling, both theoretically and experimentally, of the multiple-antenna wireless channels encountered in subway tunnels. We demonstrate that propagation is conveniently modeled by a flat-fading channel, but there exist strong spatial correlations among channel components that decrease capacity and affect receivers’ performance. Different space–time GSM receiving strategies have also been investigated. We first consider ST equalization techniques that only account for the noise and the controlled Intersymbol Interference (ISI) introduced by the modulation format employed in GSM. Then, we analyze the performance of receivers that incorporate ST coding capabilities and show the superior performance of iterative MAP (Maximum a Posteriori) receivers that interchange soft information among the equalizer and the ST decoder. All receivers are evaluated with experimental channels measured in the subway of Paris. Copyright  2002 John Wiley & Sons, Ltd.