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Secure Short-Packet Communications via UAV-Enabled Mobile Relaying: Joint Resource Optimization and 3D Trajectory Design

Milad Tatar Mamaghani, Xiangyun Zhou, Nan Yang, A. Lee Swindlehurst

TL;DR

This work tackles secure short-packet communications in UAV-enabled IoT by modeling a two-hop decode-and-forward UAV relay under latency constraints and a passive eavesdropper with location uncertainty. It maximizes the Effective Average Secrecy Throughput (EAST) by jointly optimizing per-slot transmit powers, uplink/downlink blocklengths, and the UAV's 3D trajectory, using a BSCA framework that splits the problem into three convexified subproblems. The authors derive a tractable lower bound on EAST and establish a convergent iterative algorithm that achieves near-optimal performance with polynomial-time complexity. The results demonstrate substantial secrecy-throughput gains over benchmark schemes and yield practical design insights on blocklength adaptation, power allocation, and trajectory shaping under uncertainty, highlighting the value of a joint design for secure SPC in UAV-assisted IoT networks.

Abstract

Short-packet communication (SPC) and unmanned aerial vehicles (UAVs) are anticipated to play crucial roles in the development of 5G-and-beyond wireless networks and the Internet of Things (IoT). In this paper, we propose a secure SPC system, where a UAV serves as a mobile decode-and-forward (DF) relay, periodically receiving and relaying small data packets from a remote IoT device to its receiver in two hops with strict latency requirements, in the presence of an eavesdropper. This system requires careful optimization of important design parameters, such as the coding blocklengths of both hops, transmit powers, and the UAV's trajectory. While the overall optimization problem is nonconvex, we tackle it by applying a block successive convex approximation (BSCA) approach to divide the original problem into three subproblems and solve them separately. Then, an overall iterative algorithm is proposed to obtain the final design with guaranteed convergence. Our proposed low-complexity algorithm incorporates robust trajectory design and resource management to optimize the effective average secrecy throughput of the communication system over the course of the UAV-relay's mission. Simulation results demonstrate significant performance improvements compared to various benchmark schemes and provide useful design insights on the coding blocklengths and transmit powers along the trajectory of the UAV.

Secure Short-Packet Communications via UAV-Enabled Mobile Relaying: Joint Resource Optimization and 3D Trajectory Design

TL;DR

This work tackles secure short-packet communications in UAV-enabled IoT by modeling a two-hop decode-and-forward UAV relay under latency constraints and a passive eavesdropper with location uncertainty. It maximizes the Effective Average Secrecy Throughput (EAST) by jointly optimizing per-slot transmit powers, uplink/downlink blocklengths, and the UAV's 3D trajectory, using a BSCA framework that splits the problem into three convexified subproblems. The authors derive a tractable lower bound on EAST and establish a convergent iterative algorithm that achieves near-optimal performance with polynomial-time complexity. The results demonstrate substantial secrecy-throughput gains over benchmark schemes and yield practical design insights on blocklength adaptation, power allocation, and trajectory shaping under uncertainty, highlighting the value of a joint design for secure SPC in UAV-assisted IoT networks.

Abstract

Short-packet communication (SPC) and unmanned aerial vehicles (UAVs) are anticipated to play crucial roles in the development of 5G-and-beyond wireless networks and the Internet of Things (IoT). In this paper, we propose a secure SPC system, where a UAV serves as a mobile decode-and-forward (DF) relay, periodically receiving and relaying small data packets from a remote IoT device to its receiver in two hops with strict latency requirements, in the presence of an eavesdropper. This system requires careful optimization of important design parameters, such as the coding blocklengths of both hops, transmit powers, and the UAV's trajectory. While the overall optimization problem is nonconvex, we tackle it by applying a block successive convex approximation (BSCA) approach to divide the original problem into three subproblems and solve them separately. Then, an overall iterative algorithm is proposed to obtain the final design with guaranteed convergence. Our proposed low-complexity algorithm incorporates robust trajectory design and resource management to optimize the effective average secrecy throughput of the communication system over the course of the UAV-relay's mission. Simulation results demonstrate significant performance improvements compared to various benchmark schemes and provide useful design insights on the coding blocklengths and transmit powers along the trajectory of the UAV.
Paper Structure (23 sections, 3 theorems, 52 equations, 9 figures, 2 tables, 1 algorithm)

This paper contains 23 sections, 3 theorems, 52 equations, 9 figures, 2 tables, 1 algorithm.

Table of Contents

  1. Introduction
  2. Prior Studies and Motivation
  3. Our Contributions
  4. System Model and Problem Statement
  5. Periodic Secure Short-packet Relaying
  6. System Assumptions and Constraints
  7. UAV trajectory constraints
  8. Channel modeling
  9. Constraints on radio resources and latency
  10. Secrecy Metric for SPC
  11. SR for uplink SPC
  12. SR for downlink SPC
  13. Problem Formulation
  14. Proposed Low-complexity Design
  15. Joint Power Optimization
  16. ...and 8 more sections

Key Result

Lemma 1

A closed-form lower-bound expression on the uplink short-packet secure transmission secrate_1 can be obtained as where $\bar{\gamma}_{ae}[n] = \frac{p_a[n]\rho_{e}[n]}{\|\mathbf q_a - \mathbf q_e\|^\alpha}~\forall n$, and $A_0[n]$ and $A_1[n]$ are given respectively by

Figures (9)

  • Figure 1: System model for secure UAV-aided short-packet relaying in the presence of an adversary with location uncertainty.
  • Figure 2: Illustration of periodic short-packet UAV relaying, where $\mathbf{U}$ and $\mathbf{D}$ indicate uplink and downlink transmissions, respectively. Sensitive information is generated and made available for transmission at the beginning of each timeslot $\delta_t$, with the remaining duration devoted to sensing and collecting data from the environment.
  • Figure 3: EAST performance vs. iteration index for different designs.
  • Figure 4: Designed UAV's 3D trajectory and velocity according to different algorithms.
  • Figure 5: Power allocation and optimized blocklength profiles for different designs.
  • ...and 4 more figures

Theorems & Definitions (6)

  • Lemma 1
  • proof
  • Lemma 2
  • proof
  • Lemma 3
  • proof