Terahertz Meets Untrusted UAV-Relaying: Minimum Secrecy Energy Efficiency Maximization via Trajectory and Communication Co-Design

Milad Tatar Mamaghani,Yi Hong

doi:10.1109/tvt.2022.3150011

Milad Tatar Mamaghani, Yi Hong

Open Access

https://doi.org/10.1109/tvt.2022.3150011

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Abstract

Unmanned aerial vehicles (UAVs) and Terahertz (THz) technology are envisioned to play paramount roles in next-generation wireless communications. In this paper, we present a novel secure UAV-assisted mobile relaying system operating at THz bands for data acquisition from multiple ground user equipments (UEs) towards a destination. We assume that the UAV-mounted relay may act, besides providing relaying services, as a potential eavesdropper called the untrusted UAV-relay (UUR). To safeguard end-to-end communications, we present a secure two-phase transmission strategy with cooperative jamming. Then, we devise an optimization framework in terms of a new measure $-$ secrecy energy efficiency (SEE), defined as the ratio of achievable average secrecy rate to average system power consumption, which enables us to obtain the best possible security level while taking UUR's inherent flight power limitation into account. For the sake of quality of service fairness amongst all the UEs, we aim to maximize the minimum SEE (MSEE) performance via the joint design of key system parameters, including UUR's trajectory and velocity, communication scheduling, and network power allocation. Since the formulated problem is a mixed-integer nonconvex optimization and computationally intractable, we decouple it into four subproblems and propose alternative algorithms to solve it efficiently via greedy/sequential block successive convex approximation and non-linear fractional programming techniques. Numerical results demonstrate significant MSEE performance improvement of our designs compared to other known benchmarks.

Highlights

THE unmanned aerial vehicle (UAV) has recently been recognized as one of the major technological breakthroughs to be pervasively applied in 5G-and-beyond wireless communication networks, supporting massive machine-type communications, internet of things (IoT), and artificial intelligence (AI)-empowered communications [1]–[3]
To protect the confidentiality of UAV communications against hostile entities, one promising technique is the physical layer security (PLS) that uses the characteristics of wireless channels and applies communication techniques to combat attacks without complex encryption
PLS has been exploited in a wireless-powered UAV-relay system to combat eavesdropping via maximizing secrecy rate by a joint design of UAV’s position and resource allocation [12]

Summary

Introduction

THE unmanned aerial vehicle (UAV) has recently been recognized as one of the major technological breakthroughs to be pervasively applied in 5G-and-beyond wireless communication networks, supporting massive machine-type communications, internet of things (IoT), and artificial intelligence (AI)-empowered communications [1]–[3]. The security and confidentiality of such promising wireless communication systems are of utmost concern and undeniable requirements. To protect the confidentiality of UAV communications against hostile entities, one promising technique is the physical layer security (PLS) that uses the characteristics of wireless channels and applies communication techniques to combat attacks without complex encryption. PLS has been exploited in a wireless-powered UAV-relay system to combat eavesdropping via maximizing secrecy rate by a joint design of UAV’s position and resource allocation [12]. Other efforts were made to maximize the average secrecy rate (ASR) via joint trajectory and communication design for UAV-standalone wireless system [13]– [15], for double-UAV with external jamming [16]–[18], and for secure UAV-relaying scenarios [19]–[24]. When the UAV behaves as an untrusted relay, which is called untrusted UAV-relay (UUR), with the capability of information eavesdropping while assisting endto-end communications (see [25], [26]), the system design becomes quite challenging and entirely different from the existing body of research

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