Outage Performance of Cognitive Relay Networks With Wireless Information and Power Transfer

In this paper, we consider underlay cognitive radio (CR) networks with one primary receiver, one cognitive transmitter-receiver pair, and one energy harvesting relay. The transmission power of the secondary source is opportunistically determined by its interference to the primary receiver, and the relay transmission is powered by the energy harvested from the radio-frequency observations at the relay. For the considered CR networks with simultaneous wireless information and power transfer (SWIPT), we derive analytical expressions for the outage probability, as well as their high signal-to-noise ratio (SNR) approximations in closed form. The developed analytical results demonstrate that the use of SWIPT will not cause any loss in diversity gain, but the outage probability achieved by the SWIPT-CR scheme asymptotically decays as log SNR/SNR, whereas a decaying rate of 1/SNR is achieved by a conventional CR network. Computer simulation results are also provided to demonstrate the accuracy of the presented analysis.