Opportunistic energy harvesting and energy-based opportunistic spectrum access in cognitive radio networks

Abstract

The performance of large-scale cognitive radio (CR) networks with secondary users self-sustained by opportunistically harvesting radio-frequency (RF) energy from nearby primary transmissions is investigated. Using an advanced RF energy harvester, a secondary user is assumed to be able to collect ambient primary RF energy as long as it lies inside the harvesting zone of an active primary transmitter (PT). A variable power (VP) transmission mode is proposed, and a simple energybased opportunistic spectrum access (OSA) strategy is considered, under which a secondary transmitter (ST) is allowed to transmit if its harvested energy is larger than a predefined transmission threshold and it is outside the guard zones of all active PTs. The transmission probability of the STs is derived. The coverage probabilities and the throughputs of the primary and the secondary networks, respectively, are characterized. The throughput can be increased by as much as 29%. Simulation results are provided to validate our analysis.