Evaluation of outage probability due to cochannel interference in fading for a TDMA system with a beamformer

Space division multiple access (SDMA) has attracted considerable attention as a means for increasing the capacity in cellular communications. For the service provider the smart antenna could provide a much-needed device to boost capacity by decreasing the effect of interference and thereby increase user capacity in congested areas. However, questions arise as to the best trade-offs for implementing SDMA. In this paper, we develop a tool for evaluating the use of SDMA in time division multiple access (TDMA) systems. The approach is based on evaluating the outage probability due to cochannel interference in fading at the base station of a TDMA system assuming an ideal beamformer model. The statistical model developed takes into account both spatial and temporal components of the interference signal. We use the model to then bound the performance improvement. The performance improvement is with respect to a base station employing an omnidirectional antenna. The bounds for the performance are based on looking at a range of smart antenna complexity. In addition, TDMA systems with different levels of acceptable time coincidence between the desired mobile´s signal and interfering mobiles´ signals are considered. The simulation results indicate a performance improvement spread from 8 to 36 dB