Non-Collaborative Zero-Forcing Beamforming in the Presence of Co-Channel Interference and Spatially Correlated Channels

Recent results proposed optimal zero-forcing beamforming (ZFBF) methods for non-collaborative space division multiple access systems when the base station (BS) as well as the subscriber stations (SS) are assumed to be equipped with multiple antennas [1]. Previous work assumes that fading across the transmit antenna elements at the base station (BS) is un- correlated and that there is no co-channel interference (CCI) at each of the SS. This paper extends this work in two different ways. First, we show that similar to the case of iid channels as shown in [1] the right singular vector of the channel matrix is still the optimal choice for the SS beamforming vector when the channels are spatially correlated. Secondly, we consider the effects of CCI on each SS and propose optimal receive beamformers for the SS in the presence of CCI. Further, we derive expressions for the average SNR obtained by each user under the above constraints. We verify our theoretical results using simulations.