Relay selection and power allocation for energy-efficient cooperative cognitive radio networks

In this paper, we apply the innovative multi-objective optimization methods to the challenge posed by rate maximization, total transmission power minimization and relay selection in cooperative cognitive radio networks. The proposed methods which are based on amplify and forward relaying strategy optimize the three conflicting objectives and, at same time, they maximize the rate quality, minimize the total transmission power allocated to the network relays and make the best relay node selection. The multi-objective optimization studied is a non-convex non-linear combinatorial algorithm which is converted to its convex smooth equivalent through two efficient approximation methods. We apply the multi-objective lexicographic method to overcome the challenge posed by these conflicting objectives simultaneously. The proposed relay node selection method is based on zero-norm principle which provides an effective technique to obtain a minimum node selection. Simulation results confirm that the proposed approaches offer superior performance over known schemes in terms of throughput gain and number of active relays.