Delay-Tolerant Multi-Stage Relay Type Mobile Robot Tele-Operation Method Using LoRaWAN as Sub Communication Infrastructure

In closed spaces after disasters, information gathering using mobile robots is conducted to prevent secondary disasters, such as injuries or fatalities of rescue teams. However, in such closed spaces, it is necessary for the mobile robots to establish their own communication infrastructure. Therefore, a method has been considered where multi-stage relay devices capable of relaying wireless LAN are deployed to expand the range of tele-operation. Nevertheless, there is a risk that the wireless LAN may be disconnected due to multi-stage relay device malfunctions during the mission, causing the mobile robot to become an obstacle and hindering information gathering. To address this issue, we have proposed a method when, in the event of communication disconnection with the mobile robot operating through wireless LAN, LoRaWAN is used as a sub communication infrastructure to enable retreat. However, LoRaWAN is characterized by one-way communication from the child device to the parent device. Consequently, when performing tele-operation through multi-stage relay using LoRaWAN, there is a problem of accumulated delays during continuous packet transmission. In this paper, we propose a low-latency multi-stage relay tele-operation method using LoRaWAN and demonstrate its effectiveness.