Mobile ad hoc networks powered by energy harvesting: Battery-level dynamics and spatial throughput

Wireless networks can be self sustaining by harvesting energy from ambient sources such as kinetic activities or electromagnetic radiation. In this paper, the spatial throughput of a mobile ad hoc network powered by energy harvesting is analyzed using a stochastic-geometry model where transmitters are Poisson distributed and powered by randomly arriving energy and each transmitter transmits with fixed power to an intended receiver under an outage constraint. We assume that harvested energy is stored in batteries with large capacity. The probability that a transmitter transmits, called transmission probability, is proved using the random-walk theory to be equal to one if the energy-arrival rate is larger than transmission power or otherwise equal to their ratio. This result and the stochastic-geometry theory are applied to maximize the network throughput by optimizing transmission power for a given energy-arrival rate. The maximum network throughput is shown to be proportional to the optimal transmission probability that is equal to one if the transmitter density is below a given function of the energy-arrival rate; otherwise the probability is smaller than one as derived. Moreover, the maximum network throughput is also obtained for the extreme cases of high energy-arrival rates or sparse/dense transmitters.