Quantized Feedback for Spatial Multiplexing System

In this paper we present a quantized preceding scheme for the spatial multiplexing system equipped with MMSE-SIC receiver. The preceding matrix, consisting of a beamforming matrix and a power allocation matrix, is selected to maximize the minimum post-detection SINR of the MMSE-SIC receiver. Rather than the whole beamforming matrix, the beamforming vector for each data stream is selected sequentially from a predetermined codebook. The advantage of the sequential selection is that the computational burden and storage requirements are significantly reduced while the performance degradation is marginal. This is especially appealing for mobile terminals due to their physical limitation. The codebook is constructed by the Grassmannian beamforming criterion. Moreover, the proposed scheme is flexible enough to allow for a change in the number of data streams without redesigning the codebook. Simulation results are presented to demonstrate the effectiveness of the proposed scheme.