sum-rate maximization based on power constraints for cooperative af relay networks

In this paper, our objective is maximizing total sum-rate subject to power constraints on total relay transmit power or individual relay powers, for amplify-and-forward single-antenna relay-based wireless communication networks. we derive a closed-form solution for the total power constraint optimization problem and show that the individual relay power constraints optimization problem is a quadratic programming which does not have a closed-form solution. to solve it, we propose a closed-form low-complex technique which introduces suboptimal solution as an upper bound of system sum-rate. the performance of two new proposed algorithms are evaluated in the view of average achievable sum-rate and energy efficiency in different signal to noise ratios (snrs). considering the effect of the number of relays, the effect of channel gains of the source-relay as well as the relay-destination, and also the impact of the level of imperfect csi are investigated. according to the simulation results, higher sum-rate can be achieved in total power constrained scenario for all snrs but energy efficiency is approximately the same for both of them. in addition, higher sum-rate is achievable by increasing the number of relays and/or improving the quality of uplink and downlink channels as well as decreasing uncertainty of channels