Re-configurability to channel state information reliability in space-time block coded systems

While knowledge of the channel at the transmitter can provide significant performance enhancements for wireless communications, the generation of reliable channel feedback is complicated by the rapid time variations of the channel for mobile applications. In this paper an optimal transmitter strategy, and the resulting gains are presented for multiple input multiple output (MIMO) transceivers employing space-time block coding and imperfect channel feedback. The proposed scheme exploits the knowledge on the channel state information (CSI) reliability at the transmitter for the design of a linear precoder that is based on the minimisation of the symbol error rate (union bound). For low CSI reliability values (close to zero) the proposed technique is equivalent to space-time block coding, whereas for high CSI reliability values (close to one) it is proved to be equivalent to beamforming. For intermediate CSI reliability values the proposed scheme outperforms both conventional approaches and achieves robustness against CSI reliability. The performance enhancements achieved by the proposed reconfigurable scheme are illustrated via simulations.