Wireless-powered cellular networks: Key challenges and solution techniques

Energy harvesting from ambient sources is emerging as a sustainable and environmentfriendly technique to prolong the lifetime of wireless devices. However, harvesting energy from these sources may not be feasible for quality-of-service (QoS)-constrained wireless applications. As such, dedicated wireless-powered cellular networks (WPCNs) are currently being investigated to ensure the reliability as well as improved battery lifetime of the wireless devices. With emerging WPCNs, a true wireless network can be envisioned, which is free of connectors, cables, and battery access panels, and guarantees freedom of mobility. To illustrate and understand the design requirements of WPCNs, this article first points out the key challenges of designing energy-harvesting cellular networks. These include the doubly near-far problem, the signal-to-noise ratio (SNR) outage experienced by the energy-harvesting devices located toward the cell-edge, the spatial characterization of the SNR outage zone, the additional resource consumption at energy transmitting sources, and the problems related to designing fairness-constrained user scheduling schemes. A brief overview of the related research advancements in WPCNs and a summary of their limitations are then provided. Finally, we list a few suggestions and design considerations that can potentially tackle the major challenges in emerging WPCNs and open up new research directions.