Leveraging cooperative, channel and multiuser diversities for efficient resource allocation in wireless relay networks

Relay stations can be deployed between mobile stations and base stations in a single-hop wireless network to extend its coverage and improve its capacity. In this paper, we exploit cooperative diversity, channel diversity and multiuser diversity gains in an OFDMA-based wireless relay network. We study a joint channel and relay assignment problem with the objective of maximizing a well-adopted utility function that can lead to a stable system. This problem turns out to be NP-hard. First, a mixed integer linear programming formulation is presented to provide optimal solutions. We then present three simple greedy algorithms to solve the problem in polynomial time, namely, Greedy-ChannelFirst, Greedy-RelayFirst and Greedy-Joint. We also perform a comprehensive theoretical analysis for the performance of the proposed algorithms. Our analytical results show the Greedy-ChannelFirst algorithm is a constant factor approximation algorithm which always provides a solution whose objective value is guaranteed to be no smaller than the optimal value multiplied by a constant less than 1; however, the other two algorithms do not provide a similar performance guarantee. Extensive simulation results have been presented to show that all three proposed algorithms perform very well on average cases.