Abstract
Limited feedback enables the practical use of channel state information in multiuser multiple-input multiple-output (MIMO) wireless communication systems. Using the limited feedback concept, channel state information at the receiver is quantized by choosing a representative element from a codebook known to both the receiver and transmitter. Unfortunately, achieving the high resolution required with multiuser MIMO communication is challenging due to the large number of codebook entries required. This paper proposes to use a progressively scaled local codebook to enable high resolution quantization and reconstruction for multiuser MIMO with zero-forcing precoding. Several local codebook designs are proposed including one based on a ring and one based on mutually unbiased bases; both facilitate efficient implementation. Structure in the local codebooks is used to reduce search complexity in the progressive refinement algorithm. Simulation results illustrate sum rate performance as a function of the number of refinements.
Highlights
Multiuser multiple-input multiple-output (MIMO) communication systems can use limited feedback of channel state information obtained from the receiver to perform multiuser transmission on the downlink [1]
While ring codebooks are attractive, and have a computational advantage discussed in the sequel, it will no doubt be of interest to construct other local codebooks either for other values of Nt or nonring codebooks
We present a technique for deriving a local codebook from any given codebook F
Summary
Multiuser multiple-input multiple-output (MIMO) communication systems can use limited feedback of channel state information obtained from the receiver to perform multiuser transmission on the downlink [1]. This paper proposes a new codebook design and quantization algorithm that facilitates high-resolution limited feedback beamforming. The proposed algorithm allows for high-resolution using multiple refinements; it has low-storage requirements since only a base and single local codebook need to be stored; it facilitates fast codeword search. Compared with [5, 6, 9, 10] we use the local codebook definition, scaling, and rotations operations but we propose several local codebook designs, describe how to use local codebooks to implement progressive refinement with low complexity variations, and consider multiuser MIMO communication. Our approach allows non-DFT codebooks (which are good primarily for line-of-sight channels and uniform linear arrays), allows a variable number of refinement levels, and has structure that permits reduced storage and low search complexity.
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