Performance Evaluation of Asynchronous SDMA-CDMA for Mobile Cellular System

Abstract

In the last few years, the demand for mobile communication services hasincreased tremendously. However, there is no proportionate increase in the spectrumallocated. As a result, there is an urgent need for new techniques to improve systemspectral efficiency, therefore maximizing the capacity of cellular system. SDMA(Space Division Multiple Access) integrated with CDMA (Code Division MultipleAccess), resulting a system which combines between the robustness against MultipleAccess Interference (MAI) of the SDMA and the multiuser capability of CDMA whichis reflected on the performance of the SDMA-CDMA system. In this paper the BERperformance of asynchronous (Uplink) CDMA mobile cellular system was simulated,taking into account Rayleigh fading channel, convolutional encoder, Viterbi decoder,and Rake Receiver. Simulation results was agreed with theoretical results fordifferent, system parameters such as number of users, spreading factors, number ofmultipath, Rake fingers, adjacent interfering cells, , and coding ratio. When antennadirectivity was introduced, results shows that the SDMA-CDMA system has asignificant performance improvement over that of a conventional CDMA system.