Role Selection for Energy Harvesting Cooperative Systems

This paper investigates the feasibility of deploying dynamic role selection (ROSE) mechanism in three-node energy harvesting (EH) cooperative relay systems. A benchmark case of fixed role configuration is first studied which shows that full diversity order can be achieved and the system outage probability at high signal-to-noise ratio (SNR) is determined by the scaling laws of log c₀/c₀² together with log(log c₀)/c₀², with c₀ denoting the transmit SNR at the source. Then, the ROSE mechanism is merged into the EH cooperative system and it is analytically shown that the ROSE mechanism can enhance the system diversity order to three, and the high-SNR outage behavior is no longer affected by the log c₀ and log(log c₀) factors. Interestingly different from the conventional EH relay system with fixed role configuration, in the high SNR regime our results show that the energy conversion efficiency and the power-splitting factor at the relay have negligible effect on the outage behavior of ROSE cooperation.