Multiple-UAV-Assisted SWIPT in Internet of Things: User Association and Power Allocation

Abstract

Simultaneous wireless information and power transfer (SWIPT) has sparked a wave of interest in research, while unmanned aerial vehicles (UAVs) can offer a high level of service for Internet of Things (IoT) due to its deployment flexibly. In this paper, we employ multiple UAVs as transmitters to realize information-transmitting and energy-transferring for ground IoT devices simultaneously to expand the capacity and coverage of the network, where each UAV is associated with multiple ground devices. This paper investigates joint optimization of three-dimensional (3D) locations, user association and power allocation of the UAVs with the aim of maximizing the minimum data rate among multiple dispersed users on the ground while guaranteeing the energy requirement of each user. Meanwhile, the proposed optimization problem contains the transmit power budget of each UAV and constraints on user association. The feasibility analysis ensures that the problem can be solvable. To address the combinatorial optimization problem, nonconvex problems are decomposed into two subproblems. Then they are transformed into a series of convex problems alternately via successive convex optimization technique. Subsequently, we develop a multivariable iterative algorithm to settle the overall problem. Next, the convergence performance of the proposed algorithm is confirmed. In conclusion, simulation results operated under various parameter configurations substantiate the proposed algorithm can achieve a higher data rate compared with other benchmark schemes. INDEX TERMS Simultaneous wireless information and power transfer, unmanned aerial vehicles, 3D locations, user association, power allocation.

A Prospective Look: Key Enabling Technologies, Applications and Open Research Topics in 6G Networks

“…However, these schemes are not always feasible in practice and do not provide fundamental solutions to the involved energy inefficiency problem [186]. In this context, SWIPT has been foreseen as an emerging energy-replenishment solution, in which drones harvest energy from received RF signals to extend the cruising duration [187]- [189]. Despite their remarkable advantages, SWIPT-enabled drones are more vulnerable to physical layer attacks, such as eavesdropping, spoofing and jamming attacks, due to the LOS and broadcast features of drone channels.…”

Energy Efficiency Characterization in Heterogeneous IoT System With UAV Swarms Based on Wireless Power Transfer

“…χ is the additional loss to the free space propagation loss which is caused by the NLoS link, and α is the air-toground path loss exponent. It is worth highlighting that the probability of receiving LoS and NLoS groups is vastly higher than that of multipath fading [5]. Therefore, the impact of multipath fading is neglected.…”

“…Typically, IoT systems consist of small, energy-constrained nodes, and these nodes cannot continue working for a long periods of time and at long distances [5]. In some special scenarios, such as forest fire warning and pipeline inspection, the batteries of these IoT nodes cannot be manually replaced or recharged; thus the system performance is limited due to the energy constraints of the IoT device [6].…”

Joint Position and Resource Optimization for Multi-UAV-Aided Relaying Systems

“…One studies the optimization of UAV trajectory and position, and air-to-ground channel models in recent years and tries to integrate UAVs into 5G communication systems to enhance the system performance by utilizing some unique characteristics of UAVs, such as the high line of sight (LoS) links' possibility [1]. Moreover, in the literature, UAVs have been widely applied as base stations [2], [15], [16], [19]- [22], [28], [29], relays [3], [17], [18], [24]- [27], wireless chargers [4], data collectors/disseminators [5], [23], and mobile edge computing (MEC) servers [6].…”

“…It maximizes the sum rate of all nodes by optimizing the UAV's trajectory and nodes' powers. Reference [4] uses multiple UAVs to transmit information and energy simultaneously to ground users to maximize the minimum user rate while guaranteeing the energy demands of users by optimizing UAVs' trajectories and resource allocations. Reference [5] uses a UAV as a mobile relay to serve ground users in a variety of modes of practical interest.…”