Wireless energy harvesting in cognitive radio with opportunistic relays selection

In this paper, we propose an improved cognitive radio (CR) model in which the secondary system can harvest energy from the primary system and access the spectrum of the primary system to transmit its own data in an underlay mode. This model exploits the benefit of spatial diversity at the destination of the secondary system by selecting a best relay among multiple decode-and-forward (DF) relays. The outage probability of the secondary network is evaluated as a function of the maximum transmit power at the secondary transmitter (ST) under a constraint of peak interference power at the primary receiver (P R), the energy harvesting period at ST, the path loss for the channels between primary and secondary networks. The numerical results are presented to show significant improvement in the performance of the secondary system.