Quantized multiple-input multiple-output (MIMO) beamforming systems use predesigned codebooks for the quantization of transmit beamforming vectors. The quantized vector, which is conveyed to the transmitter using a low-rate feedback channel, is used for transmission to provide significant diversity and array gain. The codebook for quantization is a function of the channel distribution, and is typically designed for fixed channel distributions. In this paper, we propose a channel adaptive feedback strategy for arbitrary channel distributions, and present a simple codebook design methodology based on the channel statistics. The codebook for quantization is dynamically chosen from a structured set of pre-designed codebooks, called the codeset, wherein all codebooks are derived from one mother codebook. Simulations illustrate that the proposed method can improve error rate performance in correlated and/or channels with strongly line-of-sight components.
Paper is available here.