Cooperative radio communications over correlated shadowing: Outage analysis

In cooperative radio communication systems multiple relay nodes are used with receiver combining of the relayed and direct paths in order to combat fading outages. In this paper, different cooperative configurations are examined and novel analytical formulas and numerical results on the outage performance over correlated lognormal channels are presented. More specifically, the considered cooperative systems consist of a single relay forming a fundamental cooperative triangle-shaped configuration or two relays in arbitrary positions forming a diamond-shaped cooperative system. Moreover, the analysis covers both the Selection Combining (SC) and the Maximal Ratio Combining (MRC) at the receiver and the Fixed Relaying cooperative protocol. The performance of the proposed cooperative systems is compared with a direct link system, in order to investigate the benefits of cooperation over non-cooperation, as well as the benefits of utilizing an extra relay. The proposed expressions for the outage probability can be directly applied to various propagation scenarios where the lognormal distribution is used to describe the large scale fading effects such as, indoor, urban and on body propagation environments. Finally, the impact of the lognormal parameters (including correlation) on the cooperative system performance is investigated through extended numerical results.