Distributed Approaches to Exploit Multi-user Diversity- 09/23/2005

XiangPing (Sandra) Qin

In this talk, we consider the uplink medium access problem in a multi-user wireless fading environment. In a multi-user fading system, for any given time, one of the users is likely to have a good channel; an effect referred to as multi-user diversity. Much of the previous work requires a centralized scheduler with knowledge of each user's channel state information. The overhead required to estimate channel states for such approaches may be prohibitive. Therefore, we consider distributed medium access control (MAC) schemes where each user has knowledge of its own fading level. We propose simple variations of some classic random access schemes: channel-aware Aloha and splitting algorithms. Performance is analyzed in different scenarios and compared to the centralized scheme. It is shown that multi-user diversity is still exploited by distributed approaches and the optimal throughput can be approached with small overheads.