Joint Power and Location Optimization of Relay for Amplify-and-Forward Cooperative Relaying

In this work, joint optimization of Power Allocation (PA) and Relay Location (RL) is investigated for Amplify-and-Forward (AF) cooperative relaying in order to minimize the Average Symbol Error Rate (ASER). First, a closed-form expression of the ASER is derived for different modulations in Rayleigh fading channel at a high signal-to-noise ratio regime based on moment generating function. Second, we optimize the RL for the AF cooperative relaying with any given power assignment at the source and the relay. Finally, we develop a closed-form explicit formula for joint RL and PA optimization which is a standard fix-point problem. Evaluation of the effect of path-loss exponent demonstrates that in a lossy channel, relay location closer to the source yields better performance. Finally, extensive numerical results and simulation comparisons confirm that the minimum ASER can be achieved via the joint PA-RL optimization.