Energy harvesting random underlay cognitive networks with power control

摘要

Spectrum and energy constraints are fundamental barriers to the future growth of wireless communication networks, and to break this gridlock is the promise of energy harvesting cognitive radio (CR) networks. To this end, this paper investigates the feasibility of energy harvesting underlay CR networks with the primary system employing power control. We consider primary and underlay nodes distributed randomly in R as homogeneous Poisson point processes (PPP). Underlay transmitters scavenge power from primary transmitters, and are able to transmit as long as they are outside a guard region surrounding a primary receiver. The primary and underlay systems are assumed to perform power control based on path loss inversion, and that a underlay transmitter requires N charging slots to fully charge its batteries after depletion. We consider two cases of power depletion after a underlay transmission: 1) full power depletion, and 2) partial power depletion based on distances to the intended receivers. We derive the probability of a successful charge by mapping the PPP of primary transmitters to an equivalent PPP incorporating random transmit powers, and use a Markov chain to derive the probability of a successful transmission while incorporating temporal effects for the two aforementioned power depletion scenarios. We show that the probability of successful transmission is not greatly affected by the guard distance, and that it drops by approximately 10 fold for each 15 dB increase in the threshold received power level required for an energy harvest. We further show that energy harvesting is most feasible when the threshold power required for a harvest is lower than the receiver sensitivity of a primary receiver.