Transmit optimization for spatial multiplexing in the presence of spatial fading correlation


Rohit U. Nabar, Helmut Bölcskei, and Arogyaswami J. Paulraj


IEEE Global Telecommunications Conference (GLOBECOM), San Antonio, TX, Vol. 1, pp. 131-135, Nov. 2001.

DOI: 10.1109/GLOCOM.2001.965093

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Multiple-input multiple-output (MIMO) wireless systems employ spatial multiplexing to increase data rate. The performance of spatial multiplexing is highly dependent on channel statistics which in turn depend on antenna spacing and richness of scattering. It has been shown in [10] that the presence of transmit correlation can have a detrimental effect on the performance of multi-antenna signaling techniques. In this paper, we present a novel scheme to (partly) mitigate the performance loss of spatial multiplexing in the presence of highly correlated fading at the transmitter. The adaption to be performed at the transmitter is a form of power allocation and/or relative phase adjustment between the different symbol streams to be multiplexed. We consider the cases of dual-polarized as well as uni-polarized antennas and derive estimates of the uncoded symbol error rate as a function of power allocation and phase adjustment. We then optimize power allocation and phase adjustment and demonstrate that this form of preprocessing can yield SNR gains of up to 4dB over the case where no precoding is employed.


Spatial multiplexing, MIMO wireless, fading correlation, transmit optimization

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