Energy harvesting-based spectrum access model in overlay cognitive radio

In this paper, we propose an energy harvesting-based spectrum access model in overlay cognitive radio (CR). In the proposed scheme, one of potential secondary transmitters (STs) is selected to help a primary transmitter (PT) forward primary signals to a primary receiver (PR). The chosen ST harvests energy from the PT´s signals to serve the PT-PR communication as well as find opportunities to access licensed bands. Moreover, the primary network employs incremental cooperative communication in which the PR requires the assistance from the STs only when the transmission between PT and PR is not successful. For performance evaluation, we derive lower-bound closed-form expressions of outage probability for both secondary and primary networks over Rayleigh fading channel. Monte-Carlo simulations are performed to verify theoretical results. The results present that the outage performance of the primary network can be enhanced significantly due to the cooperation of the STs, while that of the secondary network mainly depends on the transmit power of the PT.