Cooperative relay assignment for static energy-constrained networks

Cooperative communication has become an efficient technology to improve the spatial diversity. Among this, relay assignment significantly affects power consumption of the entire network. This paper first analyses the relationship between power consumption and the number of relay nodes. Then, we define the relay assignment k-RA problem where k is the maximum number of relay nodes participating into each cooperative transmission pair, and k = 1 or 2. We design an optimal algorithm ESRA to solve the 1-RA problem. The proposed algorithm transforms this problem into bipartite matching, and assigns relay nodes to transmission pairs based on the matching result. Next, a heuristic algorithm ETRA is presented for the 2-RA problem. The theoretical analyses show that ETRA can provide a good approximation of the optimal one. The simulation results show that ESRA and ETRA will decrease the power consumptions about 45.8% and 51.7% compared with direct transmission scheme under many situations.