Capacity of MIMO wireless channel with finite scattering in cellular systems

Abstract

The authors investigate the capacity of a finite scatterers channel model in a cellular environment for the up-link of multiple-input multiple-output (MIMO) systems. They estimate the statistics of the multi-user interference expected in a typical cellular system based on a simulation model of a cellular frequency reuse system. They treat interference as correlated noise, and pre-whiten the interference-plus-noise using a spatially-whitened matched filter. It is found that using this channel model, in a cellular system, the mutual information of a MIMO system is still significantly greater than that of a single-input single-output (SISO) or single-input multiple-output (SIMO) system, although the latter is closer. A cluster size of unity gives a larger system capacity than for cluster size 3. It is found that in a cellular MIMO system, similar to that in single links, increasing both antenna spacing and number of scatterers of the channel model can significantly increase the capacity by reducing the spatial correlation. At lower SNRs, the capacity of this finite scattering channel can achieve that of the independent Rayleigh channel with sufficiently rich scattering and sufficiently large antenna spacing. However, at higher SNRs, this can be achieved even when the spatial correlation is still significant. In addition, it is noted note that in a cellular system the standard deviation of the distribution of the MIMO capacity is quite large owing to the widely varying location and power of interferers.