Weighted DFT Codebook for Multiuser MIMO in Spatially Correlated Channels.
ABSTRACT This paper proposes a novel codebook for multiuser multiple-input multiple-output systems under spatially correlated channels. Existing codebooks designed for correlated channels either require accurate channel statistics which is not favorable for practical systems, or only perform well in highly correlated channels. In this paper, we first analyze the per-user rate loss led by using DFT codebook, then propose a two-level codebook, named weighted DFT codebook. It consists of a DFT-based codebook and a Grassmannian linear packing codebook. The proposed scheme does not need accurate channel statistics and can adapt to both correlated and uncorrelated scenarios. Simu- lation results show significant performance gain of the proposed codebook over the existing codebooks in various correlated channels. Index Terms—Limited feedback, MU-MIMO, WDFT, Code- book
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ABSTRACT: Multiple-input multiple-output (MIMO) wireless systems provides capacity much larger than that provided by traditional single-input single-output (SISO) wireless systems. Beamforming is a low complexity technique that increases the receive signal-to-noise ratio (SNR), however, it requires channel knowledge. Since in practice channel knowledge at the transmitter is difficult to realize, we propose a technique where the receiver designs the beamforming vector and sends it to the transmitter by transmitting a label in a finite set, or codebook, of beamforming vectors. A codebook design method for quantized versions of maximum ratio transmission, equal gain transmission, and generalized selection diversity with maximum ratio combining at the receiver is presented. The codebook design criterion exploits the quantization problem's relationship with Grassmannian line packing. Systems using the beamforming codebooks are shown to have a diversity order of the product of the number of transmit and the number of receive antennas. Monte Carlo simulations compare the performance of systems using this new codebook method with the performance of systems using previously proposed quantized and unquantized systems.IEEE Transactions on Information Theory 01/2003; 49:2735-2747. DOI:10.1109/ICC.2003.1204421 · 2.65 Impact Factor
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ABSTRACT: Limited feedback enables the practical use of channel state information in single user and multiple user MIMO (multiple input multiple output) 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 by multiuser MIMO communication is challenging due to the large size codebooks required. This paper proposes a progressive refinement concept that uses a base codebook quantization followed by a progressively scaled local codebook to enable high resolution quantization and reconstruction.Signals, Systems and Computers, 2008 42nd Asilomar Conference on; 11/2008
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ABSTRACT: We analyze the sum-rate performance of a multi- antenna downlink system carrying more users than transmit antennas, with partial channel knowledge at the transmitter due to finite rate feedback. In order to exploit multiuser diversity, we show that the transmitter must have, in addition to directional information, information regarding the quality of each channel. Such information should reflect both the channel magnitude and the quantization error. Expressions for the SINR distribution and the sum-rate are derived, and tradeoffs between the number of feedback bits, the number of users, and the SNR are observed. In particular, for a target performance, having more users reduces feedback load.IEEE Journal on Selected Areas in Communications 09/2007; 25:1478-1491. DOI:10.1109/JSAC.2007.070920 · 4.14 Impact Factor