Recommended network infrastructure

[romzn]

Description

• The rpi 4B on the rae act as an WiFi router
• All connected clients are in one subnet and can communicate to each other
• The * Robot Control Unit* talk over the rae with the users host computer
• Multiple host-computer of the researchers can be connected what makes collaborative research on one system comfortable

Acceptance Criteria

• Diagram of the network topology
• links to recommended USB WiFi interfaces
• Setup of the users host to communicate via ROS

[romzn]

WiFi Interface test

Tested an USB Stick TP-Link Archer T3U AC1300

The drivers has to be installed manually:

git clone https://github.com/cilynx/rtl88x2bu.git
cd rtl88x2bu
VER=$(sed -n 's/\PACKAGE_VERSION="\(.*\)"/\1/p' dkms.conf)
sudo rsync -rvhP ./ /usr/src/rtl88x2bu-${VER}
sudo dkms add -m rtl88x2bu -v ${VER}
sudo dkms build -m rtl88x2bu -v ${VER}
sudo dkms install -m rtl88x2bu -v ${VER}
sudo modprobe 88x2bu

After loading the drivers the sticks works.

Results

Signal strength is measured with nmcli d wifi list

same room

With a distance of 1 meter

device       BSSID                      SSID                    MODE   CHAN  RATE        SIGNAL  BARS  SECURITY 
Laptop       E4:5F:01:01:BC:E1  rae                      Infra        36    135 Mbit/s  **100**     ▂▄▆█  WPA2 
Stick          E4:5F:01:01:BC:E1  rae                      Infra        36    135 Mbit/s    **90**      ▂▄▆█  WPA2

With a distance of 2 meters

Device       BSSID                      SSID                     MODE   CHAN  RATE        SIGNAL  BARS  SECURITY 
Laptop       E4:5F:01:01:BC:E1  rae                        Infra       36       135 Mbit/s  **84**      ▂▄▆█  WPA2 
Stick          E4:5F:01:01:BC:E1  rae                        Infra       36       135 Mbit/s  **84**      ▂▄▆█  WPA2   

With a distance of 2 meters and running realsense node

DEVICE      BSSID                      SSID                     MODE   CHAN  RATE        SIGNAL  BARS  SECURITY
Laptop        E4:5F:01:01:BC:E1  rae                        Infra       36       135 Mbit/s     **84**      ▂▄▆█  WPA2 
Stick           E4:5F:01:01:BC:E1  rae                        Infra       36       135 Mbit/s     **69**      ▂▄▆█  WPA2 

Different room

sitting in the next room 1 Wall ~ 4m

Device      BSSID                      SSID                     MODE   CHAN  RATE        SIGNAL  BARS  SECURITY 
Laptop      E4:5F:01:01:BC:E1  rae                        Infra       36    135 Mbit/s    **37**      ▂▄__  WPA2  
Stick         E4:5F:01:01:BC:E1  rae                        Infra       36    135 Mbit/s    **46**      ▂▄__  WPA2  

Conclusion

If the realsense-node is in operation the singnal-strength decreases from 85% to 70%, with a distance of 2 m between rae and host. This should be enough for streaming the depth images.
The antenna gain of the module is enough for an nearby operation. If it is necessary to have a better performance there is also the same module with an antenna available. TP-Link-Archer-T3U-Plus-