Multicast to Unicast

Over wifi multicast is limited to a very low rate. However I’ve read about using multicast to unicast to get a higher rate. Doing a little research it looks like this is enabled in cfg80211 however I can’t seem to find any examples or information on how to enable it. Is this possible with the wifi hardware running in AP mode on the jetsons?

danpollock,

Yes, below are the steps to enable wifi AP.

  1. Turn OFF Wi-Fi (Pre-requisite)
  2. Connect ethernet cable to tegra to give it internet source
  3. Turn ON wireless hotspot on tegra using GUI interface
    (i) To allow SSID broadcasts, the following bcmdhd module paramter should be set: op_mode=2. Set this in two ways:
    a) manually via /sys/module/bcmdhd/paramters/op_mode node
    ->echo 2 > /sys/module/bcmdhd/parameters/op_mode
    b)or to set the parameter automatically on boot, add a bcmdhd.conf (module conf fine, the name may change) file to /etc/modprobe.d with this line:
    options bcmdhd op_mode=2
    (ii) Create a new connection in “Network Connection” settings using GUI
    a) Click Network icon on GUI -> Edit-connections -> click “Add” button
    b) Choose Wi-Fi from dropdown
    c) In Edit window enter custom “Connection name”, SSID, select device MAC address (primarliy of wla0)
    d) Under WiFi-Security select WPA and WPA2 Personal and give a passcode
    e) Under IPv4 Setting select “Shared to other computers”
    f) In newly created system-connection file for your hotspot, change mode=ap
    For e.g. sudo vim /etc/NetworkManager/system-connections/

and set mode=ap in the given file

(iii) Turn ON Wi-Fi, to enable hotspot
(iv) Your hotspot is ready to use now
4. Connect other (client) device to this hotspot and access network using it
5. Repeat above for 2-3 iterations and have (client) device connected to this hotspot for sometime

Yes I have done all that. And I’m running a rtsp gstreamer pipeline on it with no issues. However this needs to talk to a ground station and a phone. I know the IP addr of the ground station but not the phone at boot up. I’ve written some scripts to get the ip of the phone but multicast would be so much easier and more bullet proof. Problem with running multicast is it works at the slowest rate so any device can connect over wifi. This is way to slow for decent video. Using multicast to unicast the speed goes back up to the highest rate the wifi can handle. So I’m trying to implement that on the jetson. Looks like you configure it in cfg80211 but I can’t figure out how to do it or if its possible on the tegra.

danpollock,

It sounds interesting, but I got confused in some statement in previous comment.

“Problem with running multicast is it works at the slowest rate so any device can connect over wifi. This is way to slow for decent video. Using multicast to unicast the speed goes back up to the highest rate the wifi can handle.”

So the target is to use unicast to receive the IP of each device?