iTUAVs: Intermittently Tethered UAVs for Future Wireless Networks

We propose the intermittently tethered unmanned aerial vehicle (iTUAV) as a trade-off between the power availability of a tethered UAV (TUAV) and flexibility of an untethered UAV. An iTUAV can provide cellular connectivity to an area while being temporarily tethered to the most adequate ground anchor. Also, it can flexibly detach from one anchor, travel, and then attach to another one to maintain and improve the coverage quality for mobile terrestrial users. Hence, we discuss in this article the existing UAV-based cellular networking technologies, followed by a detailed description of the iTUAV system, its components, and mode of operation. Subsequently, we present a comparative study of the existing and proposed systems highlighting the differences of key features, such as mobility and energy availability. To emphasize the potential of iTUAV systems, we conduct a case study, evaluate the iTUAV performance, and compare it to benchmark systems. Obtained results show that with only 10 anchors in the area, the iTUAV system can serve up to 90 percent of the users covered by the untethered UAV swapping system. Moreover, results for a small case study illustrate that the iTUAV system allows to balance performance and cost, as well as be implemented realistically. For instance, when user locations are clustered, the iTUAV system with only two active iTUAVs and four possible anchor locations, outper-forms a system with three TUAVs, while when considering a single UAV on a 100 minutes mission, a system with only six anchors already outperforms a freely flying UAV as it combines location flexibility with increased mission time.