Performance analysis of opportunistic relaying and opportunistic hybrid incremental relaying over fading channels

In this study, the authors develop and present a comprehensive analysis of two opportunistic cooperative relaying schemes for long term evolution (LTE)-advanced networks operating over generalised-K and Nakagami-m fading channels. They present and compare the performance of opportunistic relaying (OR) and opportunistic hybrid automatic repeat request incremental relaying (OHIR). They analyse performance in terms of the average symbol error rate for both conventional OR and OHIR LTE-advanced networks with the radio channel modelled as composite generalised-K fading (encompassing both fading and shadowing) and Nakagami-m fading channels. They also analyse the outage probability for OR operating over these channels. Both the theoretical analysis and simulations confirm that for conventional OR LTE-advanced networks operating over composite generalised-K fading channels, a diversity order of k(N + 1) is achieved when shadowing is more severe than fading, and a diversity order of m(N + 1) is achieved when fading is more severe than shadowing (where k and m represent the generalised-K distribution shape parameters and N represents the number of candidate relays for the OR selection). The simulation results confirm the accuracy of the analytical expressions developed in this study. It is evident from the theoretical analysis and simulations that, for a similar quality of service as that for OR, OHIR not only reduces the amount of required radio resources but also maintains the full diversity order.