Unreliable wireless latency

Hello,

Currently operating 3 Jetson TX1s on an isolated network. When connected to WiFi, TX1 communications are completely unreliable: latency anywhere between 50 ms and 5000 ms. On Ethernet, latency is a smooth, consistent 2.5 ms.

Problems:

  • Cannot start or use ad hoc network
  • Cannot use external router WiFi to get reliable latency

Currently, the setup is 3 TX1s connected via Ethernet to a router. The ideal setup would not involve the router at all, but use the on-board wireless adapters with an ad hoc network.

I’ve tested the wireless devices on all 3 Jetsons, and it does not seem to be a hardware problem. All Jetsons are running at maximum performance, as well.

Any insight is most appreciated.

-Matthew

Hello Matthew,

Which server daemon do you use? hostapd ,network manager or else?

Hey, thanks for the quick response.

I’m using whatever comes stock with Ubuntu 16.04 LTS. I flashed JetPack L4T 2.3.1 on all of them before I did anything.

Not sure if there’s a command I can run to give you more specific information.

Matthew,
What WiFi channel and external router are you using? It may influence your perf.

Matthew,

Besides, I want to make sure what is your network topology. How do you test your result between wireless and ethernet?

Sure thing.

Our goal is to have a single TX1 host an ad hoc network for communications between the other two. The external router is a non-ideal workaround.

The external router is a Belkin Pre-N Wireless Router, model # F5D8230-4

We’re operating in the following mode: 802.11g&802.11b (2.4 GHz)

Channel is automatic.

To test the result, we ping from one TX1 to another.

Hi mjones,

As what I understood, ideally you want 3 TX1 can communicate with each other.

I am still working on init ad-hoc mode and the performance issue. If you are urgent, please try wifi-ap mode first. This would help you build an isolated network but still different from ad-hoc.

Hey WayneWWW,

Yes, that’s right. Currently, there is a problem using wifi on any of the TX1s. Namely, when they are connected to a wireless network via wifi adapter, latency is very poor (~3000 ms). We’re hoping to address this issue, as well.

Thanks for your feedback!

Hi Matthew,

Please use a wifi analyzer to see if there are other channels which is more clear and try to change channel.
This may help improve the quality.

I’ve tried a number of different channels.

The best results I’ve observed give good latency initially (~50 ms), but quickly devolve. I get a few solid packets through, then back to ~1000-5000 ms latency.

Tested on standard channels (1, 6, 11), and nonstandard channels (2, 3, 4, 8, 10).

Please try GUI setting to set ad-hoc mode.
http://howtoubuntu.org/how-to-create-a-wireless-ad-hoc-network-in-ubuntu

Also, this chip has power-saving feature and would cause higher unstable latency.

Use these command to turn it off.

iw dev wlan0 set power_save off #- to disable power save and reduce ping latency.
iw dev wlan0 get power_save # will return current state.

Hi mjones,

Have you done the experiment by our suggestion?
Any result can be shared?

Thanks

WayneWWW and kayccc,

I apologize for my delayed response!

I used the aforementioned commands, and set up an ad hoc network, but could not get any TX1 to connect to the TX1 hosting the network. It would hang for quite some time trying to resolve the connection, and then tell me it couldn’t connect.

I set up the ad hoc network by doing the following:

  • Clicked WiFi symbol in upper-right corner
  • Clicked "Create New Wi-Fi Network"
  • Gave it an SSID, and a password

To test if latency improved, I connected the TX1s to a router, and pinged them from one of the TX1s. The results seemed better, but not reliable. I would get a few instances of latency times on the order of 50 ms, but then it would shoot up to 1000 ms every third or fourth message.

It is not usual to have 1000ms latency. Could you setup a wifi ap mode and test it again?

The router should be removed to verify the performance of TX1-TX1 connection.

If you don’t know how to setup wifi ap. Please let me know.

This thread talks about setting up an access point:
https://devtalk.nvidia.com/default/topic/910608/?comment=4976505

Thanks linuxdev!

So I’ve got one TX1 set up as an access point (hotspot in Ubuntu 16.04), and the ping latency tends to be between 15 and 30 ms. Occasionally, latency jumps to 100ish ms.

Is this considered standard operating performance?

P.S. I’ve set the TX1s to maximum performance, too.

Could you move to a cleaner band to test the performance again??

Yes. Updates soon.

WayneWWW,

Moved to 5 GHz band, different channel. Seeing a very steady 15 ms latency.

Is this typical performance?

Yes, it looks like a typical perf.