Energy outage and achievable throughput in RF energy harvesting cognitive radio networks

In radio frequency (RF) energy harvesting (EH) cognitive radio network (CRN), the EH secondary users (SUs) access an idle channel to transmit data and an occupied channel to harvest energy. Therefore, the EH SUs can reliably transmit data only if sufficient energy and an idle channel are available. In this paper, we analyze the probability that the EH SUs may completely run out of energy and the achievable throughput of the EH SUs is derived accordingly. To improve the throughput of the SUs, we consider a 2-channel sensing scheme that the EH SUs are allowed to sequentially sense up to 2 channels to further search for the opportunities for data transmission. Consequently, the opportunities for data transmission increase, while less opportunities are available for energy harvesting. To validate the proposed analysis, we use the Monte-Carlo simulation to show an agreement between the analytical and simulated values, and the simulation results turn out to be reasonably acceptable.