Opportunistic Waiver of Data Reception for Exploiting Multiuser Diversity in the Uplink of IEEE 802.11 WLAN

In this paper, we consider how to exploit multiuser diversity in the uplink of IEEE 802.11 WLAN when its uplink and downlink are asymmetric. In the uplink, there is no central node that arranges transmission schedules of all stations. To overcome this limitation, we devise a novel MAC protocol, called WLAN Opportunistic Waiver (WOW), where an access point (AP) indirectly controls transmission instants of stations by not sending a CTS frame if the received signal strength (RSS) of an RTS frame is below a certain threshold that is station- dependent. We develop an analytic model for WOW with a three- dimensional Markov chain. We can find the optimal threshold to maximize the system throughput. To avoid optimization burdens, we propose a simple algorithm which can determine a near- optimal threshold. Both analysis and ns-2 simulation results show that the throughput of WOW increases with the number of stations and the improvement compared with Receiver Based Auto Rate (RBAR) is up to 43 % while maintaining access fairness as achieved by IEEE 802.11.