SRT-based cooperative video transmission protocol for inspection of small diameter sewer pipes using multiple drifting wireless cameras

It is difficult to inspect the inside of small-diameter sewer pipes safely, quickly, and at low cost using existing inspection methods such as human visual inspection and wired robots. We have proposed a sewer pipe inspection system that uses multiple drifting wireless cameras (drifting nodes) to realize safe, quick, and low-cost sewer inspection. In this system, drifting nodes are put into the pipes, and the video recorded inside the pipe is transmitted to relay servers (Access Points, APs) temporarily deployed in utility holes via wireless communication. To realize this system, we have developed a cooperative video transmission protocol, Sewer Video Transmission Protocol (SVTP), in which multiple drifting nodes that move in the same pipe send the video of different parts of the pipe. The recent implementation of SVTP (SVTP 2022) uses SRT (Secure Reliable Transport) as the transport protocol in order to handle the rapidly changing quality of wireless links between a drifting node and an AP. However, SVTP 2022 has several implementation issues; a drifting node needs a long time to detect that it is out of the communication range of an AP, and packets are frequently retransmitted in the early stage of an SRT session between an AP and a drifting node. In addition, the performance of video transmission using multiple drifting nodes with SVTP 2022’s implementation had not been evaluated. In this paper, we present the design and implementation of an improved version of SVTP, SVTP 2023, which solves the implementation issues of SVTP 2022, and show the results of video transmission experiments using multiple drifting nodes.