Precoding for Multi-user MIMO Interference Channel: A Signal Set Separation Problem

We consider precoder designs in K-user MIMO interference channel when finite signal constellations are employed at the transmitters. Recognizing that the interferences seen at each receiver form a set of discrete points around the desired signal, the precoders are designed such that the separations between the signal sets are maximized at every receiver. Several precoder designs are proposed based on how the distances between the signal sets are defined. The considered distance metrics aim to directly minimize the average bit error rates. At low and high SNR regions, the resulting precoders may be either solved in a closed form or computed efficiently using nearest-neighbor search algorithms. Our simulation results show significant improvements in terms of bit-error-rate performance and receive diversity over a wide range of SNRs and number of users as compared to several conventional algorithms.