Research and Development of Sewerage Infrastructure Sensing System Using Unlicensed Band Multi-hop LPWA

Due to global warming, sudden urban disasters, such as urban flooding caused by localized heavy rainfall and large-scale sinkholes due to aging sewer infrastructure, are becoming a major problem. Regarding inland flooding in particular, there are already examples of initiatives to predict inland flooding through simulations based on inland flood analysis models. However, there are many cases of unexpected disasters that are difficult to predict through simulation alone, such as unidentified water. Therefore, in addition to simulations, it is becoming more effective to monitor the condition of the sewer system below the manhole in real time on the ground using various sensing data such as water level sensors, water flow sensors, and environmental sensors. Because steel manhole covers are generally disadvantageous from a wireless communication perspective, there are several examples of sensing initiatives using mobile networks and cellular systems (licensed bands) LPWA with high signal strength. In this study, we have realized a flexible and scalable multi-hop WSN communication system that can monitor sewerage infrastructure using unlicensed LPWA, without using mobile networks or cellular LPWA. The system utilizes a multi-hop WSN of unlicensed band LPWA to receive weakened radio signals transmitted through the manhole cover at a repeater above the manhole, and then transmits them via multi-hop to a remote location. The system's effectiveness was confirmed through a demonstration experiment using an actual manhole site. We will continue to build a platform that aims to enable multimodal sensing of real-time water level sensing data, open weather data, and video data of the ground around the manhole.