Ros2 humble bandwidth usage limited to 3MiB/s

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Hello,

I have a turtlebot4-lite (ran by rPi4, ubuntu 22.04, ros2 humble), from which I'm streaming rgb and depth images (from oak-d lite camera).

Whenever I'm streaming only the rgb image to a remote PC, it works perfectly. However, whenever I try to stream depth as well, fps of rgb image slows down. After a bit of inspecting I figured out that the max network usage (when subscribing to one, 2 or 3,.. topics) is always 3Mb/s. So If i just stream the depth image, the network usage is 3Mb/s. If I also subscribe to RGB image, the rate of depth images falls down, so the bandwidth is still 3Mb/s. No matter how many topics I subscribe to, the network usage is always 3Mb/s. I tried copying files from rPi to remote PC, and the data rate was much higher than 3Mbps, so I the problem must be related to ROS2.

The processor on rPi is used only around 20%, so the bottleneck can't be rPi. I also changed the routers, and the result is the same. Does ROS2 have some setting that limits the max bandwidth used?

Thanks for your help!

EDIT: I'm using fastDDS.

EDIT 2: when I switch the network to 5Ghz, the data rate climbs to 6Mbps. Better but still way too little.