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Mobile users scattered in a microcell and communicating with co-located base station antennas, may cause a severe near-far problem for an uplink space division multiple access (SDMA) system. Also correlations within the multi-input multi-output (MIMO) channel matrix, in such uplink SDMA propagation scenario, can cause significant degradation in system performance. In this paper, we investigate the above problems. We propose to distribute the base station antennas, as multi- antenna arrays, at different sites in the microcell and deploy a correlation reduction algorithm. A significant improvement in the performance of the SDMA system is evident.

The near-far problem and the correlations in a MIMO channel are two major obstacles in the way of widely implementing Space Division Multiple Access (SDMA) systems. In this paper we investigate the effect of distributing the basestation antennas and the reduction of intra-user correlations on the performance of a MIMO-OFDM system in which a basestation, composed of distributed antenna arrays, is communicating (downlink transmission) with several single antenna mobile users. The arrays are located at different sites in a Ricean-Lognormal channel environment. Very significant improvement in system performance is achieved due to the improved spatial properties of the MIMO channel and due to the reduction of channel matrix correlations.