A Hybrid Reactive Routing Protocol for Decentralized UAV Networks

TL;DR

The paper tackles routing in decentralized UAV networks with dynamic topologies and congestion, proposing Hyd-AODV, a hybrid reactive protocol that discovers routes on-demand while monitoring a local 2-hop pipe around the active route to enable preemptive switching. It combines multi-metric route selection with AoI-based queue management and a pipe-based information exchange to reduce route discoveries and control overhead. Theoretical analysis and ns-3 simulations show Hyd-AODV achieving higher throughput and lower signaling overhead than AODV and LEPR, while approaching the performance of proactive schemes like MCA-OLSR under various network densities, speeds, and data rates. The work clarifies the trade-offs of pipe width and locality, and suggests extensions to accommodate channel variability and alternative UAV mobility models for improved robustness.

Abstract

Wireless networks consisting of low SWaP, FW-UAVs are used in many applications, such as monitoring, search and surveillance of inaccessible areas. A decentralized and autonomous approach ensures robustness to failures; the UAVs explore and sense within the area and forward their information, in a multihop manner, to nearby aerial gateway nodes. However, the unpredictable nature of the events, relatively high speed of UAVs, and dynamic UAV trajectories cause the network topology to change significantly over time, resulting in frequent route breaks. A holistic routing approach is needed to support multiple traffic flows in these networks to provide mobility- and congestion-aware, high-quality routes when needed, with low control and computational overheads, using the information collected in a distributed manner. Existing routing schemes do not address all the mentioned issues. We present a hybrid reactive routing protocol for decentralized UAV networks. Our scheme searches routes on-demand, monitors a region around the selected route (the pipe), and proactively switches to an alternative route before the current route's quality degrades below a threshold. We empirically evaluate the impact of pipe width and node density on our ability to find alternate high-quality routes within the pipe and the overhead required to maintain the pipe. Compared to existing reactive routing schemes, our approach achieves higher throughput and reduces the number of route discoveries, overhead, and resulting flow interruptions at different traffic loads, node densities and speeds. Despite having limited network topology information, and low overhead and route computation complexity, our proposed scheme achieves superior throughput to proactive optimized link state routing scheme at different network and traffic settings. We also evaluate the relative performance of reactive and proactive routing schemes.

Figures (11)

• Figure 1: Illustration of autonomous UAV ad-hoc network for remote monitoring of an inaccessible area, where a communication infrastructure is not available.
• Figure 2: Modules used in the proposed Hyd-AODV routing scheme.
• Figure 3: A UAV can randomly change its trajectory, which would change the LLT value of the pair. Therefore, the LLT value is computed when the link is formed or either UAV in the pair changes its trajectory garg2022accurategarg2021adaptive.
• Figure 4: Pipe formation in Hyd-AODV routing scheme.
• Figure 5: Possible situations to connect two nodes in a network. As the pipe width $W$ increases, more route segments become available to connect the nodes.