Performance Comparisons of Optimal Power Allocation over Nakagami-m and Rayleigh Fading Channels in Wireless Cooperative Systems

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Cooperative wireless communication has been newly proposed in wireless communication systems for discovering the inherent spatial diversity in relay channels. The Amplify- and-Forward (AF) cooperation protocols with multiple relays have not been sufficiently examined; however, it has a low complexity in terms of application. Through this article, we evaluate a cooperative diversity technique whereby a source broadcasts some data to a destination with the assistance of multiple relay nodes with AF protocols, by taking into account the challenge of allocating power to be able to increase the total capacity of AF and also enhance resource utilization. We analyse the optimality of how much the power should really be allocated at the source as well as relays system by optimizing the symbol error rate (SER) performance in a useful method on the basis of Rayleigh and Nakagami- m fading. Firstly, we derive a closed-form SER formulation for MPSK signal making use of the idea of moment generating function (MGF) and some statistical approximations in high signal to noise ratio (SNR) for the system under studied. We therefore determine a tight corresponding lower bound, which converges to the identical limit the same as the theoretical upper bound, after that develops an optimal power allocation (OPA) strategy with mean channel gains over Rayleigh and also Nakagami- m fading to reduce the SER. Simulation results prove that our approach using Nakagami- m fading outperforms the (OPA) using Raleigh fading scheme and is tight with the theoretical approximation based on the SER upper bound in high SNR for a different number of relays .  Index Terms—Wireless communication, amplify-and-forward, symbol error rate, Nakagami- m fading, power allocation.