Submitted to IEEE Journal on Selected Areas in Communications, Sept. 2009.
In this paper, we propose jointly optimized transceiver algorithms called interference aware coordinated beamforming (IA-CBF) for a two-cell system where each base station is equipped with multiple transmit antennas. The case of single stream transmission to two mobile stations with two or more receive antennas is considered. First we propose minimum-mean-square-error IA-CBF using a lower bound on the achievable sum rate. Next we derive optimal (under an assumption of zero other-cell interference) and suboptimal transmit beamforming vectors called zero-forcing IA-CBF. We also investigate the optimality of the proposed IA-CBF algorithms with respect to the number of receive antennas. Analytical and numerical results confirm that the proposed system with two transmit/receive antennas achieves full degrees of freedom (a.k.a. multiplexing gain) of the two-cell multiple-input multiple-output channel while showing a better sum rate performance than the conventional solutions such as non-cooperative eigen-beamforming and interference nulling.