Implementation of A Bi-Directional Intermittent Wireless Multi-Hop Transmission Method for Multiple UAVs Control and Video Streaming

Maintenance of sewer pipe infrastructure is costly and time-consuming. To tackle this problem, we have been developing a sewer pipe inspection system using multiple UAVs (unmanned aerial vehicles). In the inspection system, multiple UAVs form a multi-hop network to extend the communication range of $\mathrm{Wi}-\mathrm{Fi}$ in small-diameter pipes. The leading UAV, which is equipped with a camera, transmits the recorded video data to a control node on the ground via relay UAVs while the control node sends control commands to the UAVs to manage their positions. For this multi-hop transmission of UAV control commands and video data, our previous work has proposed a packet transmission scheduling method based on the Bi-IPT (Bidirectional Intermittent Periodic Transmit) protocol. In this paper, we report on the implementation of the proposed scheduling method and evaluate its performance through experiments in a communication environment using coaxial cables. Specifically, we conducted experiments over a multi-hop network having four nodes, transmitting dummy data to simulate video data. Experimental results confirmed that the proposed method achieves a significantly lower packet loss rate and higher throughput than conventional transmission methods that do not control transmission timing.