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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