TDMA Achieves the Same Diversity Gain as Opportunistic Scheduling in Relay-Assisted Wireless Networks

Opportunistic scheduling has been recognized as an effective method that significantly outperforms fixed TDMA scheduling in both channel capacity and communication reliability. Nevertheless the superior system performance comes at a price of high computational complexity, large signaling overhead, and unfairness among users. In this paper, we find that in relay-assisted next-generation wireless networks, fixed TDMA scheduling achieves the same diversity gain as opportunistic scheduling, as long as the best relay is carefully selected. Moreover, by introducing very limited opportunism, TDMA scheme yields the same optimal outage probability attained by full scale opportunistic scheduling at high SNR. In other words, we can safely enjoy the advantages of opportunistic scheduling without suffering its drawbacks. We also propose a simple distributed algorithm to implement our scheme. Our results here may find wide application in next-generation wireless communication systems, as relay-assisted cellular system is one of the major architectures in 4G wireless system included LTE or WiMAX.