Joint relay assignment and power allocation for cooperative communications

In the recent years, cooperative communication is shown to be a promising technology to improve the spatial diversity without additional equipments or antennas. With this communication paradigm, energy can be saved by effective relay assignment and power allocation while achieving the required bandwidth for each transmission pair. Thus, this paper studies the joint relay node assignment and power allocation problem which aims to minimize the total power consumption of the network while providing the efficient bandwidth service. We first analyze the minimum power consumption under the bandwidth requirement for different communication modes. Based on the analytical results, we present a polynomial-time algorithm JRPA to optimally solve this problem. The algorithm first constructs a weighted bipartite graph G based on the given transmission pairs and relay nodes. Then, we adopt the KM method to find out a saturated matching M, and assign the relay nodes to the transmission pairs based on the matching. The optimality of the algorithm is also proved. The simulation results show that JRPA algorithm can save about 34.2% and 18.9% power consumptions compared with the direct transmission and ORA schemes in many situations.