An MGF approach for performance evaluation of non-regenerative cooperative relay networks with adaptive modulation and optimum power allocation in nakagami-m fading environments

This article analyzes the performance of CSI-assisted cooperative amplify-and-forward (CAF) relay networks that employ both the optimal power allocation strategy among collaborating nodes and adaptive M-ary quadrature amplitude modulation (MQAM) technique in Nakagami-m wireless fading environments. In particular, we advocate a simple yet unified numerical approach based on the marginal moment generating function (MGF) of the total received SNR to derive tight approximations or upper and lower bounds for the average bit error rate (ABER), mean achievable spectral efficiency, and outage probability performance metrics. The proposed analytical framework is sufficiently general to characterize the performance of adaptive-link CAF relay networks over a wide range of fading distributions (i.e., not restricted to Rayleigh fading) with independent but non-identically distributed (i.n.d) fading statistics across the spatially distributed diversity paths. Numerical results reveal that the optimal transmit power allocation among cooperative nodes in a practical CAF relay topologies could lead to a further substantial increase in the mean spectral efficiency compared to the equal power assignment case but at the expense of higher network overhead. The accuracies of our analytical results have been validated via Monte Carlo simulations.