Sensing-Based Spectrum Sharing in Cognitive Radio Networks

In this paper, a new spectrum sharing model called sensing-based spectrum sharing is proposed for cognitive radio networks. This model consists of two phases: in the first phase, the secondary user (SU) listens to the spectrum allocated to primary user (PU) to detect the state of PU; in the second phase, SU adapts its transit power based on the sensing results. If the PU is inactive, the SU allocates the transmission power based on its own benefit. However, if the PU is active, interference power constraint is imposed in order to protect the PU. By studying the ergodic capacity of SU, we show that this spectrum sharing model can achieve a higher capacity of SU link and improve the spectrum utilization compared to conventional opportunistic spectrum access or simple spectrum sharing. Using the dual decomposition method, we find the optimal power allocation policies and the optimal sensing time for fading channels to achieve the ergodic capacity of the SU link considering both transmit and interference power constraints. Finally, the numerical results are presented to validate the analytical results.