A UAV-Enabled Wireless Powered Sensor Network Based on NOMA and Cooperative Relaying With Altitude Optimization

Non-orthogonal multiple access (NOMA) is envisioned as a promising technology that enhances the spectrum efficiency for future cellular networks. On the other hand, there is a growing interest in wireless powered sensor networks toward the sustainable realization of Internet of Things (IoT), as they may not require any battery replacement in principle. Moreover, the use of unmanned aerial vehicle (UAV) as a moving access point or base station has emerged as a potential solution to the high traffic demands of wireless networks. This article focuses on the UAV-aided data collection from multiple wireless powered sensor nodes, where a single-antenna UAV supplies all the sensor nodes located in the coverage area with energy for data transmission, with which the sensor nodes send back their information to the UAV. We study several transmission schemes including NOMA as well as cooperative relaying, together with two representative sensor node pairing strategies. Based on the theoretical analysis in terms of the achievable outage probabilities as well as the corresponding numerical results, we elucidate suitable node pairing strategies that depend on selected transmission schemes.