UAV-Mounted Aerial Relays in Military Communications: A Comprehensive Survey

TL;DR

This paper addresses the challenge of maintaining robust military communications in contested environments by evaluating UAV-mounted aerial relays (AR) as dynamic alternatives to fixed terrestrial relays (TR). It develops a military-focused taxonomy, contrasting active aerial relays (AAR) with aerial reconfigurable intelligent surfaces (ARIS), and introduces the Mission-Critical Relay Effectiveness Score (MCRES) with Algorithm 1 to guide scenario-driven relay selection (AR vs TR and AAR vs ARIS). The work combines qualitative assessments of coverage, mobility, security, and cost with a quantitative framework that weights six doctrine-derived attributes to optimize relay choices under diverse missions such as dynamic battlefields, EW, or covert operations. These contributions offer a structured path toward resilient, adaptable, and secure UAV relay networks, while outlining key challenges and future research directions in power, security, autonomy, and multi-domain network integration.

Abstract

Relays are pivotal in military communication networks, expanding coverage and ensuring reliable connectivity in challenging operational environments. While traditional terrestrial relays (TR) are constrained by fixed locations and vulnerability to physical obstructions, unmanned aerial vehicle (UAV)-mounted aerial relays (AR) offer a dynamic and flexible alternative by operating above obstacles and adapting to changing battlefield conditions. This paper provides a comprehensive survey of AR systems in military communications, presenting a detailed comparison between AR and TR paradigms and examining two specific AR technologies: active aerial relays (AAR) and aerial reconfigurable intelligent surface (ARIS) relays. The survey delves into their operation, benefits, challenges, and military applications, supported by a qualitative analysis across metrics such as coverage, flexibility, security, and cost. A novel multi-dimensional metric, the mission-critical relay effectiveness score (MCRES), is introduced as a quantitative method for evaluating relay suitability based on mission-specific weights for critical attributes like mobility, jamming resilience, deployment speed, stealth, coverage, and autonomy. Furthermore, we present Algorithm 1, a decision-making framework that leverages the MCRES to guide the systematic selection of the optimal relay type, AR or TR, and subsequently AAR or ARIS, tailored to the unique demands of a given military scenario, such as dynamic battlefield operations, electronic warfare, or covert missions. Finally, the paper addresses current implementation challenges and outlines promising future research directions to advance the deployment of robust and resilient UAV-mounted relay systems in contested military environments.

Figures (14)

• Figure 1: Number of research papers on using UAVs in communication systems. Source: IEEE Xplore
• Figure 2: Structure of the paper: The labeled height of each green cylinder approximates the length of its corresponding section.
• Figure 3: Military UAV Classifications.
• Figure 4: The U.S. Department of Defense UAV Classifications
• Figure 5: Features of some UAVs categorized as MALE UAVs whose altitude $\le 9$ km and range$>200$ km, and HALE UAVs whose altitude $>9$ km and having indefinite range.