Journal of Communications
In this paper, the authors consider 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 sub problems which are power allocation and relay selection.