Cooperative relay assignment in wireless networks

Cooperative communication is shown to be a promising technology to significantly increase the transmission rate of wireless network. However, most of the existing results on relay assignment problem with multiple source-destination pairs are limited to assign each single pair at most one cooperative relay node. Moreover, for a given pair, the rate gain obtained by employing multiple cooperative relay nodes for cooperative communication may be greater than that can be obtained by selecting only a single cooperative relay node. Therefore, this paper studies the cooperative relay node assignment problem in a network environment, where multiple source-destination pairs compete for the same pool of cooperative relay nodes and each pair can employ multiple cooperative relay nodes for cooperative communication to maximize the minimum rate among all pairs. We first formulate this problem into a 0-1 non-linear integer program and then develop a polynomial-time approximation algorithm to solve this problem. This approximation algorithm iteratively increases the rate of the pair with minimum rate among all pairs and can achieve the approximation ratio of Δ, where Δ is the maximum number of neighbor cooperative relay nodes for each source node in the network. The simulation results show that this algorithm can increase the network performance by about 56% and 65% comparing with ORA and NCR schemes respectively.