QUANTIZED MULTI-RANK BEAMFORMING WITH STRUCTURED CODEBOOK FOR MULTIPLE-ANTENNA SYSTEMS

摘要

A quantized multi-rank beamforming technique that is adapted based on feedback from a receiver containing information that captures the existence of multiple transmission modes of the channel between the transmitter and receiver. The modes of the channel can be represented by a set of orthonormal eigenvectors. Rank selection chooses the optimum number of modes for transmission in order to maximize the transmitted rate or guarantee the highest reliability based on the channel state information provided through the feedback link. In order to fully exploit the feedback, which is typically limited, different codebooks for different ranks are provided. Such a rank-specific codebook design can considerably improve the performance by allowing finer quantization of the transmission space. Power control across the various modes can also be provided. A power control strategy assigns a different fraction of the transmit power to each mode based on the feedback. The power control information can be included in the codebooks.