Exploiting spatial diversity in rate adaptive WLANs with relay infrastructure

The throughput capacity of a wireless local area network (WLAN) can be improved synergically by 1) the multi-rate capability of modern WLAN equipments and 2) the spatial diversity provided by its relay infrastructure. In this work, we investigate the effect of multi-path fading and opportunistic utilization of a fixed number of immobile relay nodes on the throughput capacity of a rate adaptive WLAN. We develop an analytical framework that computes the throughput capacity of an IEEE 802.11 WLAN with relay infrastructure in the Rayleigh fading environment. We compare the performance of MAC-layer and network-layer relaying. Our results show that up to 200% performance gain can be achieved by an optimal relay infrastructure over a network with no relay. Furthermore, for a wide range of system parameters, optimally placed relay nodes can significantly increase the network throughput capacity