## 6 Discussion  
In this study, the performance of a VLC modem in an underwater inspection and intervention task was analyzed, particularly focusing on network control for image transmission in scenarios where misalignments, distance, poor visibility, and different light conditions affect the connection and bandwidth. To break down the problem and try to understand how the position, orientation, and misalignment of the underwater robot with respect to the GCS affect the bandwidth, the authors designed some experiments to measure the bandwidth of the connection when the robot was developing a trajectory. The experiments conducted in controlled underwater conditions revealed that the VLC modem achieved high bandwidth at the short distances tested (maximum 12 m). Regardless of the misalignment angle, as long as the modems are in the field of view of the each other and the conditions are optimal (low light, good visibility, and short distances) high bandwidths such as 6 Mbps can be achieved. The field of view stated by the manufacturer is 120 degrees, and experimental results show that the FoV calculated for the different trajectories in the tank was around 115 degrees. It is important to mention that the water in the tank was clear, the light conditions were optimal, and the glass of the control room reflected some of the light. The use cases prove that the network control algorithm performs well when the robot develops an intervention task where the bandwidth changes continuously. In both cases, the operator interacted with the HRI, indicating the image priority parameters. It is important to mention that there can be some disturbances, such as misalignment, as well as changes in light conditions and water visibility, that can affect the quality of the signal and cause changes in the bandwidth. Other internal disturbances can also affect the state of the network, such as an increase in the amount of data transferred. One example is when the operator increases the requirements of either of the two images, the other one is disturbed. In this case, the network controller continuously adapts the parameters of the image depending on the real state of the network, avoiding network congestion problems. The visual light communication alternative to communicate I-AUV is a viable solution when the characteristics of the mission are not optimal to use an umbilical cable. However, it is important to take into account the amount of data transferred, so image compression and point cloud compression are recommended options. It is also important to design  
Figure 17: Network congestion control of the search and recovery use case. the mission to occur as much as possible in the FoV of the I-AUV. If this is not possible, design autonomous behaviors can be designed to recover the connection going to a home position (aligned to the VLC modem). Another solution is to use a a docking station or an umbilically connected ROV to follow the I-AUV to the intervention area, but this solution needs a cooperation algorithm, increasing the complexity of the intervention. Future work in this research line consists of exploring different image compression tools such as Webp, as well as increasing the immersion of the operator in the HRI with tools for visualization of point clouds. This is particularly complex because transferring point clouds through a VLC modem can overload the network, resulting in loss of control of the robot. To avoid network congestion, an algorithm to compress point clouds can de developed. Conceptualization, S.L.-B., P.J.S. and R.M.-P.; methodology, S.L.-B., P.J.S. and R.M.-P.; software, S.L.-B., R.M.-P. and S.R. ; validation, S.L.-B., R.M.-P., S.R. and J.E. ; formal analysis, S.L.-B., P.J.S., R.M.-P., S.R. and J.E. ; investigation, S.L.-B., P.J.S., [PERSON]-P. and J.E. ; resources, S.L.-B., P.J.S., [PERSON]-P. and J.E. ; data curation, S.L.-B., P.J.S., [PERSON]-P. and J.E. ; writing--original draft preparation, S.L.-B. and R.M.-P.; writing--review and editing, S.L.-B., P.J.S., R.M.-P., S.R. and J.E.