JOINT POWER AND BANDWIDTH ALLOCATION FOR MULTIUSER AMPLIFY AND FORWARD COOPERATIVE COMMUNICATIONS USING PARTICLE SWARM OPTIMIZATION

Joint power and bandwidth allocation for multiuser single relay amplify and forward cooperative network is addressed. Conventional resource allocation schemes based on equal distribution of bandwidth and/or power may not be efficient given the constrained power and bandwidth at the relay node. Joint power and bandwidth allocation is proposed based on maximization of the sum rate of all users. For a given user bandwidth, frequency division multiplexing (FDM) is used; part of the data is transmitted through the relay, and the other part is transmitted using the direct link. The achieved data rate using AF (with amplification gain proportional to instantaneous channel information of the source-relay link) for a single user is not jointly-concave function in the power and bandwidth profiles. Based on the optimal power and bandwidth allocation for every user, the data either transmitted solely using the direct link, or transmitted using the relay link on part of the bandwidth and the direct link on the other part. For this scenario, the problem is formulated as a mixed integer nonlinear optimization problem. Conventional optimization schemes can not be used. Particle swarm optimization (PSO) is used to solve the formulated problem. Numerical results demonstrate the effectiveness of the proposed scheme, and shed interesting throughput-fairness trade-off in the resource allocation problem.