CORRELATION AND MIMO COMMUNICATION ARCHITECTURE ( INVITED )

In this paper, we give an overview of MIMO architecture and the impact of correlation on its operation using the correlation matrix approach. First, we derive a universal upper bound on the MIMO channel capacity, which is not limited to a particular scenario, using the Jensen’s inequality. This bound accounts for both transmit and receive branch correlation in such a way that the impact of these branches can be estimated separately, which simplifies the procedure substantially. Some simple analytical results, which quantify the impact of correlation on the MIMO capacity in an explicit way, are given. We show that correlation increase is equivalent to SNR decrease in some cases. The concept of MIMO effective dimensionality is further introduced. Using a block correlation matrix model, we show that the effect of correlation is to decrease the effective dimensionality. We also discuss the paradox of zero correlation and provide a statistical explanation for it. We demonstrate why zero mean correlation is not a guarantee of high capacity. Finally, we introduce the concept of adaptive MIMO architecture and discuss the fading reduction provided by it.

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