Institute of Electrical & Electronic Engineers
The authors consider how to efficiently employ D2D communications for Secondary Users (SUs) in a cognitive cellular network. In this network, Primary Users (PUs) transmit via base station normally, while SUs can employ multiple transmission modes. One is to transmit via Base Station (BS mode), and the other is to employ D2D communication (D2D mode) due to the scarce idle spectrum. The SUs who have the potential to transmit to each other using D2D mode form a group. Within this group, they can transmit to each other via BS mode or using D2D mode directly. Outside this group, only BS mode is available.