Performance of cooperative diversity networks: Analysis of amplify-and-forward relaying under equal-gain and maximal-ratio combining

By enhancing diversity, cooperation in wireless networks allows increasing the transmission reliability and extending the radio coverage, without the need of implementing multiple antennas at the terminals. In this context, this paper proposes a general approach for analyzing the performance of dual-hop cooperative diversity networks with nonregenerative variable-gain relays. Such a strategy allows for the use of both equalgain combining (EGC) and maximal-ratio combining (MRC) techniques at the destination. In our analysis, closed-form approximations for the outage probability (OP) and average symbol error rate (SER) of linear modulations are presented. These expressions yield results instantaneously, regardless the number of relays used, in contrast with exact solutions which are rather intricate and difficult to evaluate, especially when the number of relays increases. The inherent simplicity of our methodology makes it attractive to serve as a benchmark in the design and performance evaluation of cooperative networks with variable-gain relays and employing either EGC or MRC. Numerical results are provided and compared with Monte Carlo simulations to illustrate the accuracy of the proposed expressions.