Energy Efficiency and Hover Time Optimization in UAV-based HetNets

TL;DR

This paper proposes an energy-efficient UAV-based HetNet framework that optimizes power and hover time, significantly improving system energy efficiency and UAV operational duration in scenarios like hotspots or disaster zones.

Contribution

It introduces a novel two-layer optimization scheme for power and hover time in UAV-based HetNets, enhancing energy efficiency and UAV service duration.

Findings

System EE improves with optimal power allocation.

Hover time optimization extends UAV flight duration.

Significant performance gains over maximum power allocation.

Abstract

In this paper, we investigate the downlink performance of a three-tier heterogeneous network (HetNet). The objective is to enhance the edge capacity of a macro cell by deploying unmanned aerial vehicles (UAVs) as flying base stations and small cells (SCs) for improving the capacity of indoor users in scenarios such as temporary hotspot regions or during disaster situations where the terrestrial network is either insufficient or out of service. UAVs are energy-constrained devices with a limited flight time, therefore, we formulate a two layer optimization scheme, where we first optimize the power consumption of each tier for enhancing the system energy efficiency (EE) under a minimum quality-of-service (QoS) requirement, which is followed by optimizing the average hover time of UAVs. We obtain the solution to these nonlinear constrained optimization problems by first utilizing the Lagrange multipliers method and then implementing a sub-gradient approach for obtaining convergence. The results show that through optimal power allocation, the system EE improves significantly in comparison to when maximum power is allocated to users (ground cellular users or connected vehicles). The hover time optimization results in increased flight time of UAVs thus providing service for longer durations.