Improving the Spectral Efficiency of Amplify-and-Forward Cooperative Relay Network with Adaptive M-QAM Modulation

This paper investigates the performance of cooperative amplify-and-forward (CAF) relay networks with adaptive M-ary quadrature amplitude modulation (M-QAM) technique in Nakagami-m and Rice wireless fading environments. We derived closed form upper bound expression for the marginal MGF of end-to-end SNR of CAF relay system in Nakagami-m fading to compute average bit error rate (ABER), mean achievable spectral efficiency, and outage probability performance metrics. Additionally, along with the above bounding techniques, we have adopted an accurate approximate MGF of end-to-end SNR of CAF relay system to compute above mentioned performance metrics. Employing the above novel approach based on "approximate MGF" allows us to simplify the computation complexity of achievable spectral efficiency as well as ABER of CAF relay system in generalized fading environments by simply replacing appropriate single channel MGF as readily available. The accuracies of our analytical results have been validated via Monte Carlo simulations.