Cooperative Video Data Transmission for Sewer Inspection Using Multiple Drifting Cameras

Since aged sewer pipes cause severe problems such as sewer leaks and cave-in accidents, inspection of sewer systems is very important. Especially, in Japan, the greater part of sewer systems will reach their life limit in coming 10 years, many local governments have been facing a problem of high monetary and labor cost of sewer inspection and maintenance. To solve the problem, monetary and labor cost-effective schemes for sewer inspection are urgently needed. We have proposed a basic design of a sewer inspection system using multiple wireless drifting camera/sensor nodes. The system does not require any manual operations in a pipe. Thus, the labor cost and operation time can be reduced. In this system, monitoring nodes record the video of the inside of a sewer pipe when they drift in the pipe and then send the recorded video data to multiple access points (APs) placed at manholes. The wireless communication distance between the nodes and each AP is limited due to the severe communication condition in pipes. This makes it difficult to send large size video data from camera nodes to APs. In this paper, we propose a collaborative video transmission scheme in which each node is assigned to take a video of a section of a segment between APs. The scheme makes the size of video data that each node has to send to an AP during its short communication period small. Thus, it enables to reduce the number of APs to collect video and to use the system for pipes with a long interval of manholes. We discuss the detailed design of the scheme and the design of the prototype of the scheme.