A downlink pattern optimisation algorithm for a smart antenna in an indoor infrastructure WLAN

This work presents a downlink pattern optimisation algorithm for a smart antenna optimum combiner operating in an infrastructure wireless local area network (WLAN) following the IEEE 802.11a or HIPERLAN/2 standards and serving the multiple users through space division multiple access (SDMA). An indoor infrastructure WLAN scenario with four users communicating with an access point is modeled using a deterministic ray-tracing tool. The performance of the smart antenna system is studied in both the uplink and downlink for the line of sight (LOS) and multipath cases to achieve optimum performance in terms of the maximisation of signal to interference plus noise ratio (SINR) for each user. It is shown that the proposed downlink optimisation algorithm achieves better SINR values for the worst case user compared to the case where uplink optimum weights are used for downlink and that the optimal downlink patterns are not necessary the same as the optimal uplink patterns.