Single Relay Selection and Power Allocation Based on Energy Efficiency in Cooperative Cognitive Radio Network

Abstract

In cooperative cognitive network (CCNs), relay selection generally depends on the channel state information (CSI). However, over-reliance on the relay with good channel condition may result in excessive energy consumption and lower network lifetime. Most previous works focused on improving system capacity without considering energy efficiency and residual energy information (REI). In this paper, a joint single relay selection and power allocation scheme based on energy efficiency is proposed. First, we propose a novel single relay selection scheme considering both REI and CSI to balance the energy consumption and performance. Then, we formulate a maximizing energy efficiency convex problem as the optimization model under limited total transmission power of secondary users (SUs) and power constraints to primary users (PUs). According to the convex optimization theory and the Karush-Kuhn-Tucker (KKT) condition, we obtain the optimal power allocation factor and the maximum energy efficiency. It is shown through the simulation that new scheme can dynamically select the appropriate relay and adjust the power allocation. Our scheme can effectively reduce the energy consumption and improves the system lifetime.