Energy-efficient relay selection based on the outage probabilities and power allocation algorithm in spectrum sharing networks

In spectrum sharing networks with relay cooperation, secondary users can get a chance to transmit their own signals by relaying primary signals without impacting the performance of the primary system. We use an amplify-and-forward (AF) protocol, firstly, proposing a new energy-efficient relay selection scheme based on the constraint of outage probabilities, which selects the optimal relay that minimizes the total transmit power of system; Secondly, we propose an optimal power allocation scheme at relay by analysing the outage probabilities for both the primary and secondary systems which gets a balance between the outage probabilities for the primary system and that for the secondary system. Simulation results show that the proposed scheme in this paper reduces the total transmit power much more than other common schemes when realizing spectrum sharing, which achieves the goal of energy-efficient green communications.