Aerial Video Stream over Multi-hop Using Adaptive TDMA Slots

Abstract

Unmanned Aerial Vehicles (UAVs) are rapidly becoming an important tool for applications like surveillance, target tracking and facility monitoring. In many of these contexts, one or more UAVs need to reach an area of interest (AOI) while streaming live video to a ground station (GS) where one or more operators inspect the AOI and carry out fine control of UAVs position. 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. In this paper, we show that routing packets over CSMA/CA (native medium access protocol of WiFi, the most common wireless technology among UAVs) behaves poorly in this context due to link asymmetries. We propose a novel distributed, adaptive and self-synchronized TDMA protocol (DVSP) that both enhances delay and packet delivery while operating on commodity hardware and leveraging a standard UDP/IP protocol stack. We prove that DVSP converges to a global solution that minimizes delay using local information, only, thus in a fully distributed manner. Real world experiments with multiple UAVs show gains in delay up to 75%, and packet delivery up to 50%, without sacrificing goodput.