Abstract
Immediately after a disaster, such as a flood, wildfire or earthquake, networks might be congested or disrupted and not suitable for supporting the traffic generated by rescuers. In these situations, the use of a traditional fixed-gateway approach would not be effective due to the mobility of the rescuers. In the present work, a double-layer network system named LoRaUAV has been designed and evaluated with the purpose of finding a solution to the aforementioned issues. LoRaUAV is based on a WiFi ad hoc network of Unmanned Aerial Vehicle (UAV) gateways acting as relays for the traffic generated between mobile LoRaWAN nodes and a remote Base Station (BS). The core of the system is a completely distributed mobility algorithm based on virtual spring forces that periodically updates the UAV topology to adapt to the movement of ground nodes. LoRaUAV has been successfully implemented in ns-3 and its performance has been comparatively evaluated in wild area firefighting scenarios, using Packet Reception Ratio (PRR) and end-to-end delay as the main performance metrics. It is observed that the Connection Recovery and Maintenance (CRM) and Movement Prediction (MP) mechanisms implemented in LoRaUAV effectively help improve the PRR, with the only disadvantage of a higher delay affecting a small percentage of packets caused by buffer delays and disconnections.
Highlights
Over the past few years, the ubiquity of the Internet and the miniaturization of computational devices created a new paradigm called Internet of Things (IoT)
All Unmanned Aerial Vehicle (UAV) fly at the same altitude in a 2D plane; All UAVs can move with constant speed in any direction; UAVs periodically exchange their position and the list of covered Ground Nodes (GNs) with their neighbors; UAVs have access to the received power of neighboring UAVs and GNs or can estimate it based on their position; The position of the Base Station (BS) is known by all UAVs; The minimum data rate acceptable for each LoRa Wide Area Networks Protocol (LoRaWAN) link is a configuration parameter
The architecture of LoRaUAV consists of a two-layer system: the first layer is composed of GNs that transmit data using LoRaWAN, while the second layer is composed of a swarm of relay drones communicating over an Wireless Fidelity (WiFi) ad hoc network
Summary
Over the past few years, the ubiquity of the Internet and the miniaturization of computational devices created a new paradigm called Internet of Things (IoT). IoT devices are subject to very strict power constraints For this reason, a new range of low power wireless communication protocols has been developed in order to support Low Power Wide Area Networks (LPWANs) [1]. LoRaWAN gateways is dynamically deployed to provide LoRaWAN coverage during firefighting operations This mesh of flying LoRaWAN gateways will receive the data from the GNs and relay it through WiFi to the command post, where the LoRaWAN Network Server resides. Since the WiFi technology presents a higher data rate, it allows the aggregation of traffic originated from a high number of GNs. On the other hand, its shorter range is somewhat compensated by the fact that communication between UAVs takes place in LoS. Proposal and comparative performance evaluation of a system providing LoRaWAN coverage in wild area firefighting operations by means of a WiFi mesh of UAV gateways.
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