Cooperative amplify and forward in the presence of a selfish partner

In Amplify-and-Forward cooperative strategy a user acting as a relay amplifies signal received from its partner and forwards it to a destination. Due to such cooperation, the system exhibits significant performance improvement. As cooperation incurs cost, the relay has to expend its own resources (power and bandwidth) to provide a reliable communication to cooperation partner. In return, the helping partner is rewarded with the same benefits when the partner reciprocates acting as a relay. However, in practice, there are no mechanisms to ensure reciprocation in cooperative communication. Due to lack of such a mechanism, especially power-limited partners may be tempted to refuse cooperation while reaping benefits of it at no cost. The presence of such free-riders can severely degrade the envisaged performance improvement. In this paper, we investigate performance of cooperative Amplify-and-Forward (AF) in the presence of a selfish user which does not conform to rules of cooperation at all time. The relay is assumed to mimic characteristics of on-off channel where it exhibits random behaviors of cooperation and defection to hide its disposition. The performance of AF in the presence of a selfish relay is evaluated by both analysis and simulation.