MIMO-STBC Based Multiple Relay Cooperative Communication Over Time-Selective Rayleigh Fading Links With Imperfect Channel Estimates

Abstract

This paper analyzes the effect of time-selective fading arising due to node mobility and imperfect channel estimates on the end-to-end performance of multiple-input multiple-output space-time block coded multiple relay cooperative communication systems. Both dual-phase and multi-phase selective decode-and-forward relaying protocols are considered for the end-to-end communication in a multiple relay cooperative system, followed by presentation of complete analyses for the same. For each protocol, closed-form expressions are derived for the per-frame average pair-wise error probability and asymptotic error floor over independent and nonidentical time-selective Rayleigh fading links. A framework is also developed for obtaining the optimal source relay power factors for each of the above protocols, which significantly improve the end-to-end reliability of the system for a given power budget. It is shown that both the multirelay systems achieve the full diversity order (DO) when all the nodes are static and perfect channel estimates are available at each receiving node. The DO of the system reduces to that of the direct source–destination link for a scenario when only the relays are mobile. Interestingly, however, in other mobile scenarios, both the systems are limited by an asymptotic error floor with increasing signal to noise ratio. Further, the impact of DO of the source–relay and relay–destination links on the optimal source–relay power allocation is also explicitly demonstrated. Simulation results yield several important insights into the end-to-end error performance for different mobility conditions and also validate the derived analytical results.