Linear transmit beamforming and receive combining is a low complexity approach for communications in the multiuser multiple-input multiple-output (MIMO) channel. This paper proposes a full search and two low complexity coordinated algorithms where each receiver uses a quantized combining vector. Since the optimization is performed at the transmitter with channel state information from all the receivers, the receive combining vectors are (either jointly or independently) quantized at the transmitter and sent to the receivers 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 sum rate of the proposed methods using Grassmannian codebooks is close to the sum capacity of the MIMO broadcast channel, especially in the high signal-to-noise ratio (SNR) regime.
Bibliographical noteFunding Information:
Manuscript received September 28, 2007; revised July 30, 2008. First published August 29, 2008; current version published November 19, 2008. The associate editor coordinating the review of this manuscript and approving it for publication was Dr. Geert Leus. This work was supported by Samsung Electronics. The material in this paper was presented in part at the Asilomar Conference on Signals, Systems and Computers, Pacific Grove, CA, October 2006 and the IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Las Vegas, NV, April 2008.
All Science Journal Classification (ASJC) codes
- Signal Processing
- Electrical and Electronic Engineering