Precoded STBC-VBLAST for MIMO Wireless Communication Systems

A degradation in the bit error rate (BER) performance of the vertical Bell-Labs layered space-time (VBLAST) MIMO system is often due to its low minimum diversity and decoder's error propagation. To remedy this problem, a hybrid scheme that integrates orthogonal space time block codes (STBC) into the lower layers of a VBLAST system was recently introduced. However, if channel state information is available at the transmitter, this hybrid system does not necessarily outperform a precoded VBLAST. This, in turn, motivates our work in this paper, namely the joint design of a precoder and its corresponding decoder for the VBLAST-STBC hybrid system. We consider the two scenarios of a flat and frequency selective fading channels and derive complete analytical solutions for both cases. Our simulation results indicate that the BER performance of the proposed precoded hybrid system is better than all of the other schemes.