Using Opportunistic CSMA/CA to Achieve Multi-User Diversity in Wireless LAN

The throughput of an IEEE 802.11 network decreases as the number of users increases because of the increased collision probability. To improve the throughput with a large population, this paper presents an opportunistic CSMA/CA scheme that exploits multi-user diversity, while maintaining backward compatibility with the IEEE 802.11 medium access control. This method prioritizes those users having high signal-to-noise-ratio by granting earlier access to these users. A simple randomization is proposed to prevent the repeated collisions of same users caused by this prioritization. The simulation results show that the proposed method improves the throughput by as much as 100% with a large population.