Distributed Multi-User Scheduling for Improving Throughput of Wireless LAN

Carrier sense multi-access (CSMA) is a typical method to share the common channel in a wireless LAN (WLAN). It works fairly well in times of light traffic. However as the number of nodes in a WLAN increases quickly, severe collision greatly degrades network performance. In this paper we propose a distributed multi-user scheduling (DMUS) scheme to solve this problem, taking time-variant link quality and rate adaptation into account. Instead of all nodes, only nodes with high instantaneous link quality are allowed to contend for the channel. By setting a suitable SNR threshold, at any instance only a small percentage of nodes join the contention. As a result, collision is mitigated, fairness is retained by independent fading, and the total throughput is increased since transmissions are finished at higher rates. Simulation results show when there are 40 nodes in a WLAN, the DMUS scheme improves total throughput by up to 49.6% compared with the contention-free scheme, and by up to 194.6% compared with the CSMA/CA scheme.