Capacity Enhancement via Multi-Mode Adaptation

in Spatially Correlated MIMO Channels



Antonio Forenza, Matthew R. McKay, Ashish Pandharipande,  Robert W. Heath Jr, and Iain B. Collings



submitted to International Symposium on Personal Indoor and Mobile Radio Communications, Berlin, Germany, September 11-14, 2005


We consider a low-complexity adaptive MIMO transmission approach for spatially correlated channels. The proposed scheme adaptively switches between statistical beamforming, spatial multiplexing and double space-time transmit diversity, depending on the changing channel conditions. We first motivate our adaptive algorithm by deriving new closed-form capacity expressions, and demonstrating significant information theoretic improvements over non-adaptive transmission. We then present a practical switching procedure based on a simple metric derived from the estimated spatial correlation matrices and average signal to noise ratio. The practical approach is shown to yield significant improvements in spectral efficiency for typical channel scenarios.

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