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Vector Quantization of Channel Information in Linear Multi-User MIMO Systems

In this paper, we propose a new vector quantization (VQ) algorithm for encoding channel state information feedback in multiple antenna, multi-user systems operating on flat fading channels with rich scattering. We consider an approach where the receiver chooses an instantaneous throughput maximizing modulation matrix from a finite set of predefined matrices (codewords). The codebook of modulation matrices is constructed based on joint optimization of the dominant channel eigenmodes of users and separate quantization of power levels. The proposed algorithm is very flexible and can be used in a variety of system configurations, including varying number of receiver antennas and frequency selective channels. We implement the proposed algorithm on flat fading MIMO channels and show the influence of the feedback rate on system capacity. We demonstrate that, even with low feedback rate, the ergodic capacity of the proposed system closely approaches the theoretic capacity of the system with perfect channel state information at the transmitter