Random beamforming in MIMO broadcast channels with cooperating receive antennas

In a Gaussian multiple-input multiple-output (MIMO) broadcast channel, the sum rate capacity can be achieved by dirty paper coding (DPC). Nevertheless, DPC is computationally intensive and requires that full channel state information (CSI) from all users in the system is available at the transmitter. However, with partial CSI at the transmitter, random beamforming [1] can exploit the inherent multiuser diversity in the MIMO broadcast channel with several users. In this work we show that with random beamforming the cooperation of the multiple receive antennas is a better policy than no cooperation at all. To this end, we consider two receive filters: the maximum ratio combiner and the Wiener filter.