Resource Allocation in OFDMA-Based Cognitive Radio Networks via Cooperation with Primary Users

—This paper considers an OFDMA-based cooperative cognitive radio network where the secondary users (SUs) act as the relay of the primary users (PUs) while guaranteeing the quality of service (QoS) of the PUs. In return, the SUs access the spectrum licensed to PUs in both time and frequency without impacting the communication of the PUs. A joint resource allocation problem is formulated to maximize the data rate of the SUs. It is proven that the optimization problem can be decomposed into two coupled subproblems which are power allocation and relay selection. The power allocation adopts the water-filling algorithm using the Lagrangian method, and the optimal relay selection is solved by Hungarian method. Simulation results show that the proposed algorithm can bring revenue to both the PUs and SUs.