A new hybrid space-time block codes and spatial multiplexing scheme with precoding

We present a new hybrid scheme which combines space-time block codes (STBC) and spatial multiplexing (SM) to achieve both diversity and spatial multiplexing gain. We design a new precoding scheme based on the Givens rotation by utilizing the phase feedback information from the receiver. Exploiting the STBC structure embedded in the hybrid scheme, the proposed scheme enables a simple maximum likelihood (ML) detection such that the receiver complexity is reduced by a factor of 1/16 for the case of 4bps/Hz. Practical precoder designs are also provided to minimize the feedback information, while maintaining near optimal performance. Also, unlike conventional schemes which require at least two receive antennas, the proposed hybrid scheme works well with a single receive antenna. Simulation results show that the proposed hybrid scheme achieves a performance gain of 7dB at a bit error rate (BER) of 10^-4 in 2 bps/Hz spectral efficiency over other closed-loop hybrid schemes.