Quantized Maximum Ratio Transmission for Multiple-Input Multiple-Output Wireless Systems


David J. Love, Robert W. Heath Jr, and Thomas Strohmer


Proc. of IEEE Asilomar Conf. on Signals, Systems, and Computers, Pacific Grove, CA, vol. 1, pg. 531-535, Nov. 3-6, 2002.


Multiple-input multiple-output (MIMO) wireless systems can provide substantial gains in capacity and quality compared to single-input and single-output (SISO) wireless systems. Transmit antenna weightings have been shown in some cases to be a low complexity solution to improving average receive signal-to-noise ratio (SNR). However, these weighting methods require feedback. Since in practice full channel knowledge at the transmitter is difficult to realize, a technique has been proposed where the receiver sends channel state information in the form of a weight vector codebook label. The proposed codebook design method is based on a quantized version of traditional maximum ratio transmission with maximum ratio combining at the receiver. A codebook design criterion is discussed that exploits the quantization problem's relationship with Grassmannian line packing. Systems using the transmit diversity codebooks are shown to have a diversity order of the
product of the number of transmit and the number of receive antennas. Monte Carlo simulation compares the performance of systems using this new codebook method with previously proposed systems.

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