SNR-based vs. BER-based power allocation for an amplify-and-forward single-relay wireless system with MRC at destination
Hamed Rasouli, Alagan Anpalagan · 2010
Optimum power allocation improves the efficiency of wireless systems. While optimizing the average received SNR would directly result in an optimized average BER in a non-relaying system, it is not clear whether we can achieve an optimized average BER in a relaying system by optimizing the average SNR at the destination terminal. In this paper, the problem of power allocation in a single-relay wireless system with maximal ratio combining (MRC) at the destination terminal is investigated via optimizing two different objective functions: average SNR and average BER. The average SNR and average BER expressions are derived for an amplify-and-forward relaying protocol with MRC at the destination as a function of source and relay transmit powers. Based on the derived SNR and BER expressions at the destination, closed-form expressions are derived for optimum transmit power of source and relay. It is observed that the BER-based power allocation scheme achieves considerable performance improvement over the SNR-based scheme when the relay is closer to the source than destination.