Coordinated Beamforming for the Multiuser MIMO Broadcast Channel with Limited Feedforward
IEEE Trans. on Signal Processing, vol. 56, no. 12, pp. 6044-6056, Dec. 2008.
Jointly optimized linear transmit beamforming and receive combining is a low complexity approach for communication in the multiuser MIMO (multiple input multiple output) broadcast channel. This paper propose several low complexity iterative algorithms for jointly designing the beamforming and combining vectors, which enforce a zero interference requirement after combining. Since the optimization is performed at the base station with channel state information for all the users, the receive beamformers are quantized at the basestation and sent to the users via a low-rate feedforward control channel. Rate bounds are provided to estimate the impact of quantization loss on the achievable rate in Rayleigh channels. Simulations show that the proposed approach using Grassmannian codebooks approaches the sum capacity of the MIMO broadcast channel.