Wireless Communications With RF-Based Energy Harvesting: From Information Theory to Green Systems

Harvesting energy from ambient environment is a promising technology to free electronic devices from electric wire and lifetime-limited battery, which have found many significant applications in sensor networks and body-area networks. This paper investigates the fundamental limit of information transmission in a wireless communication system with RF-based energy harvesting, where a master node acts both the information source and the energy source for a child node, while only information is transmitted back from the child node to the master node. In the systemic level viewpoint, we jointly investigate the two-way information transmission between the two nodes under the unique external power supply constraint at the master node. In particular, three typical receivers are considered, including the optimum receiver, the orthogonal receiver and the power splitting receiver. We explicitly characterize the achievable capacity-rate region and discuss the effect of signal processing power consumption at the child node. We also derive the boundary of the achievable capacity-rate region, which illustrates the most energy-efficient transmission strategy of the system. Simulation results confirm the substantial gain of employing capacity-rate region achieving transmission strategies and employing optimal receivers. Moreover, we present a typical application of our results, where the required transmit power is minimized to green the system.