On the energy efficiency of the adaptive algorithm in hybrid uplink cellular networks

Energy harvesting is an increasingly attractive source of power for wireless communications devices. Microwave power transfer (MPT) delivers energy from power stations (PSs) to mobile users by microwave radiation. In this paper, we consider a network architecture where PSs are distributed in an uplink cellular network for powering mobile users. MPT transmits power to mobile devices adaptively. Transmission time is divided into cycles. One cycle consists of two parts: the charge period and the communication period. We find that the ratio of charge period and cycle χ influences the throughput of the network directly. No matter what the densities of PSs and base stations (BSs) are, there exists an optimal ratio. To maximize the energy efficiency (EE) of the network, we propose an adaptive algorithm. In the algorithm, we adjust the transmission power of PSs based on the distance between the PS and its target mobile user. Comparing with the non-adaptive one, the simulation results show that the adaptive algorithm improves the EE of network and saves a significant amount of power. When the reference distance d₀ equals to 1/3 R, the adaptive algorithm saves at least 70% energy consumption of the system, and improves the EE almost 10 times than the non-adaptive one.