Compensation of phase offsets in MIMO systems using an efficient differential STBC

Carrier-phase offset in multiple-input multiple-output (MIMO) systems is a significant practical and theoretical issue. In this paper, firstly we investigate the sensitivity of the space-time block code (STBC) to carrier-phase offset over Rayleigh flat fading MIMO channel. Then, we design an accurate third-order differential STBC (DSTBC) that allows the receiver to decode the data-symbols without any prior channel-state or any carrier-offset knowledge. This DSTBC detection scheme consists in a specific trellis diagram that involves constructive correlation between successive differential data-symbols that compensates for the channel-noise effect. At the receiver side, the well-known Viterbi algorithm designed with a particular metric provides reliable decoding process. The efficiency of the proposed scheme against random carrier-phase shift is also theoretically proven. Simulation results show the good performance of the DSTBC scheme for large carrier-phase offset range and also its ability to achieve high coding gain, as well. Negligible performance-loss from the coherent STBC scheme is also noticed.