Service differentiation in wireless LANs based on capture

We investigate the effects of using a dual transmission power scheme for quality-of-service (QoS) differentiation in IEEE 802.11 wireless LANs. By setting hosts to transmit at different power levels, we enhance the likelihood that a high-power frame gets received correctly when a collision involving frames from both power levels occurs due to the capture effect. We develop a Markov model for the IEEE 802.11 DCF in a dual transmission power system over a Rayleigh-fading channel, and use it to evaluate the resulting performance, in terms of the key metrics of throughput and delay. Specifically, we study how the performance of the service classes depends on the proportion of hosts from each service class and the transmission power ratio, and demonstrate that, counter-intuitively, this dependence may be non-monotonic