Balancing Packet Delivery to Improve End-to-End Multi-hop Aerial Video Streaming

Abstract

Unmanned Aerial Vehicles (UAVs) are becoming an important tool for facilities monitoring, target tracking, surveillance, etc. In many of these contexts, a UAV needs to reach an area of interest (AOI) while streaming data to a ground station (GS) where one or more drones are controlled by an operator. In remote areas, intermediate UAVs can act as relays and form a line network to extend range. Interactive control requires a live video stream where both throughput and delay are important, which limits the number of relays and thus maximum range. However, throughput also depends on the quality of the links. It is known that in open space scenarios, where links can be considered similar, maximum throughput is achieved with equal spacing of the relays. This is not the case near large obstacles or high interference areas, in which links can be rather asymmetric. In this paper, we address this scenario and show that maximum throughput is achieved with uneven relay spacing but balanced packet delivery ratios. We propose a new distributed protocol fit to high throughput streams on line networks that tracks and balances the quality of neighboring links by moving the relay nodes accordingly. Real world experiments with multiple AR.Drone 2.0 UAVs show that variable link length in a scenario with asymmetric links generates gains in packet delivery up to 40% and throughput up to 300%.