Improving the Ergodic Capacity of Wireless Networks Using Opportunistic Relays

In this article, we exploit a novel cumulative distribution function (CDF) based analytical framework for unifying the analysis of ergodic capacity of opportunistic relay networks with selection diversity combining (SDC) diversity transmissions at the destination node. While the traditional "all participates" cooperative amplify-and-forward (AF) relaying protocol can achieve full diversity using a virtual antenna array, there is a significant loss of spectral efficiency due to its inherent half-duplex operation that increases with number of nodes in cooperation. Opportunistic relaying selection (ORS) AF scheme with the SDC scheme is proposed to overcome this issue while also simplifying the receiver design. Selected numerical results are provided to illustrate the effects of using multiple cooperative relays, fading severity parameter and power allocation on the ergodic capacity metric. Numerical results also reveal that the opportunistic AF relaying with MRC is more desirable at the tactical edge where the received signal-to-noise ratio (SNR) is very small but the opportunistic relaying scheme with SDC at the destination node is recommended at moderate/high SNR values.