Energy-Efficient Trajectory Design of a Multi-IRS Assisted Portable Access Point

TL;DR

This paper presents an energy-efficient trajectory design for a UAV-based portable access point that incorporates intelligent reflecting surfaces and considers battery discharge effects to optimize energy use and system performance.

Contribution

It introduces a novel two-phase trajectory design framework that accounts for battery nonlinearities and IRS optimization, enhancing energy efficiency in UAV communications.

Findings

IRS modules improve global energy efficiency.

Multi-lap trajectories save more energy than single-lap.

Neglecting Peukert effect overestimates UAV flight time.

Abstract

In this work, we propose a framework for energy-efficient trajectory design of an unmanned aerial vehicle (UAV)-based portable access point (PAP) deployed to serve a set of ground nodes (GNs). In addition to the PAP and GNs, the system consists of a set of intelligent reflecting surfaces (IRSs) mounted on man-made structures to increase the number of bits transmitted per Joule of energy consumed measured as the global energy efficiency (GEE). The GEE trajectory for the PAP is designed by considering the UAV propulsion energy consumption and the Peukert effect of the PAP battery, which represents an accurate battery discharge profile as a non-linear function of the UAV power consumption profile. The GEE trajectory design problem is solved in two phases: in the first, a path for the PAP and feasible positions for the IRS modules are found using a multi-tier circle packing method, and the required IRS phase shift values are calculated using an alternate optimization method that considers the interdependence between the amplitude and phase responses of an IRS element; in the second phase, the PAP flying velocity and user scheduling are calculated using a novel multilap trajectory design algorithm. Numerical evaluations show that: neglecting the Peukert effect overestimates the available flight time of the PAP; after a certain threshold, increasing the battery size reduces the available flight time of the PAP; the presence of IRS modules improves the GEE of the system compared to other baseline scenarios; the multi-lap trajectory saves more energy compared to a single-lap trajectory developed using a combination of sequential convex programming and Dinkelbach algorithm.