Challenges of wireless power transfer for prolonging User Equipment (UE) lifetime in wireless networks

Communication technologies are striving to provide ubiquitous and cable-free communication services to users while user devices are still limited with their batteries and need wires to recharge their batteries. The recent advances in Wireless Power Transfer (WPT) are promising to charge wireless sensor networks and on-body medical devices without the need of wires or battery replacement. One natural way of scavenging energy from the environment and providing ubiquitous power is electromagnetic radiation based WPT. Recently powering up Wireless Sensor Networks (WSNs) or RFID tags via omnidirectional radiation and beamforming has been studied in several studies. Yet, the potential of exploiting wireless networks to power User Equipment (UE) such as mobile phones or PDAs has been less explored. Long distances between wireless towers and UEs as well as their relatively low transmit power are among the major bottlenecks for WPT in wireless networks. In this paper, we consider dedicated energy transmission units (DETUs) to provide power to UEs. We show that although certain amount of power can be harvested by UEs, the cost of deploying DETUs dominates the design decision. As a transitional solution, power from relays, small cell towers and WiFi hotspots can be exploited. However when WPT is in-band with information transfer there may be interruption in connectivity. We discuss the challenges of WPT in wireless networks and propose several future directions.