Robust linear precoding to compensate for antenna correlation in orthogonal space-time block coded systems

Antenna correlation has a critical impact on the performance of space-time block coded systems. In this paper linear precoding, which combats the effects of antenna correlation, is applied to orthogonal space-time block coded systems with two transmit antennas. The precoding technique exploits the knowledge of the long-term characteristics of the channel, namely the channel correlation matrix at the transmitter. For low antenna correlation values the proposed technique is equivalent to space-time block coding, whereas for high correlation values it is proved to be equivalent to beamforming. For intermediate antenna correlation values the proposed technique outperforms both schemes. The sensitivity of the proposed precoding technique to channel state information errors at the transmitter is also investigated and its robustness is demonstrated.