Experimental and theoretical capacity analysis of space-division multiple access (SDMA) with adaptive antennas

Abstract

The paper focuses on TDMA air interface techniques combined with spatial multiplexing through the space division multiple access (SDMA) method. First, results from field trials performed for a variety of operational scenarios provide experimental proof of the SDMA concept for two users. Then, the capacity of the space and time division multiple access scheme is studied with the help of simulations, but from the more general and practical point of view of the produced/achieved radiation-pattern characteristics. Up to now, the analyses for the capacity of SDMA systems have ignored the critical effects that parameters, such as the scattering of the environment, the mutual coupling among the array elements or signal mismatches, have on the produced radiation pattern. The straightforward method employed in the analysis presented here takes into account these effects and hence produces a more realistic capacity assessment. The presented results for different radiation pattern beamwidths and average sidelobe levels, different frequency reuse distances and additional interference cancellation techniques highlight the trade-offs between different performance criteria and the implications to the overall system design.