Optimal power allocation for multiuser underlay cognitive radio networks under QoS and interference temperature constraints

Power allocation is an important issue for Cognitive Radio Networks (CRNs), since it needs to consider the Quality of Service (QoS) for Secondary Users (SUs) while maintaining the interference power to Primary User (PU) below the Interference Temperature (IT) threshold. In this paper, based on Euclidean projection, we propose a distributed power control algorithm with QoS requirements to minimise the total power consumption of SUs under the time-varying channel scenario. Considering the maximum transmit power constraints and the minimum signal to interference plus noise constraints for each SU, together with the IT constraints for each PU, the power allocation problem is transformed into a convex optimization problem without auxiliary variables, and is solved by the Lagrangian dual method with less information exchange. Simulation results demonstrate that the proposed scheme is superior to the Iterative Water-Filling Algorithm (IWFA).