Minimization of the Worst-Case Average Energy Consumption in UAV-Assisted IoT Networks

The Internet of Things (IoT) brings connectivity to a massive number of devices that demand energy-efficient solutions to deal with limited battery capacities uplink-dominant traffic and channel impairments. In this work we explore the use of Unmanned Aerial Vehicles (UAVs) equipped with configurable antennas as a flexible solution for serving low-power IoT networks. We formulate an optimization problem to set the position and antenna beamwidth of the UAV and the transmit power of the IoT devices subject to average-Signal-to-average-Interference-plus-Noise Ratio (S̄INR) Quality of Service (QoS) constraints. We minimize the worst-case average energy consumption of the latter thus targeting the fairest allocation of the energy resources. The problem is non-convex and highly non-linear; therefore we re-formulate it as a series of three geometric programs that can be solved iteratively. Results reveal the benefits of planning the network compared to a random deployment in terms of reducing the worst-case average energy consumption. Furthermore we show that the target S̄INR is limited by the number of IoT devices and highlight the dominant impact of the UAV hovering height when serving wider areas. Our proposed algorithm outperforms other optimization benchmarks in terms of minimizing the average energy consumption at the most energy-demanding IoT device and convergence time.