Space-Time Block Coded Transmission with Phase Feedback for Two-User MIMO-MAC

This paper proposes a space-time block coded (STBC) transmission with phase feedback for two-user multi-input multi-output multiple access channels (MIMO-MAC). In the proposed system, the phase feedback is transmitted to only one user, which reduces the overhead of the reverse link. We derive a closed-form solution for the proposed phase feedback, in order to maximize the overall received signal-to-interference-plus-noise power ratio (SINR). This allows the receiver to separate the two users with a linear detection. We also propose an efficient search method for the phase feedback, which reduces the complexity of computation. For practical applications, the quantized feedback of the proposed system is designed. Simulation results show that the proposed system with only 1-bit feedback considerably improves the performance of the MIMO-MAC system.