Robust weighted-sum-rate based multi-stream transmission for the MIMO interference channel

We study the problem of multi-stream joint maximum sum-rate precoder and minimum mean-squared error equalizer design for interference alignment in the multi-input multi-output interference channel. Joint precoder and equalizer optimization requires alternation between the forward and reverse links and assumes perfect synchronization at each network node between the transmitters and receivers, resulting in extensive overhead and spectral efficiency loss. To overcome this serious drawback, we propose a new design approach based on weighted-sum-rate maximization assuming a virtual equalizer type at the transmitter to limit the optimization process to the transmitter side. Furthermore, we examine the achievable weighted-sum-rate when the virtual equalizer type is either matched or mismatched to the actual equalizer type used at the receivers. In addition, we quantify the performance loss due to mismatched equalizer types and demonstrate the robustness of our proposed sum-rate weighting strategy to such mismatches. Finally, we derive asymptotic performance expressions and verify their accuracy numerically, even for a moderate number of users.