Optimal Power Allocation for Coordinated Transmission in Cognitive Radio Networks

Cognitive radio (CR) technology has been developed to solve the spectrum-underutilization problem. In CR networks, the CR users have opportunities to access the licensed spectrum bands assigned to the primary users (PUs). Since the PUs have priorities to use the bands, the CR users are not allowed to generate unacceptable interference to them. In this paper, we investigate power allocation schemes for source and relay nodes in CR with direct and relay link. We show that there is a significant benefit to the system rate by jointly distributing the transmitting power. Three schemes are considered, where particularly the scheme based on analogue network coding shows significant superior performance to other two classic schemes. The optimum power allocation is derived analytically. The proposed schemes are verified by the simulations which also show the impact of different positions of relay node and the primary user locations on power allocation solutions.