Chief Delphi - Periodic lost Wi-Fi packets

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Periodic lost Wi-Fi packets

While testing in our shop with our driver's station connected directly (via Wi-Fi) to the robot access point, we have noticed periodic bursts of lost packets on the driver's station graphs. The bursts occur approximately every 2 minutes. According to the driver's station, they are usually between 80% and 100% packet loss. They are usually short in duration, but occasionally the duration and timing can be such that the driver's station reports loss of communications and the fail safes can kick in and disable the motors/etc (at first we thought the PID was flaking out on our shooter when it would hiccup while running). The bursts occur whether the robot is enabled or disabled. In the course of a 3 hr meeting, we will see 5-6 dropped COMM peg counts on the driver's station.

Our driver's stations (both are showing same behavior on 2 different access points on 2 different subnets) are laptops running Windows10.
Radio has been updated to the new firmware/configuration. 2017 driver's station software is installed.
Bursts do NOT occur when connected to the access point with an ethernet cable.
Bursts resume 4-5 min. after switching back to Wi-Fi (from wired).
I tried disabling all services on the adapter except IPv4, disabling firewall, netbios, DNS registration, etc. I tried all of the various wireless options associated with the NIC itself, etc. (I have a 2 page list of things I tried so far).
I talked to other teams and they are seeing similar behavior.

Has anyone else seen these dropped packets? Has anyone found a cause/solution for them?

I know that on the field, the driver's station is connected via a wired connection, but the engineer in me cannot be completely satisfied that the problem will not appear at competition (since the connection from FMS to robot is Wi-Fi) until I know the cause (or a reasonable explanation) of the problem.

Re: Periodic lost Wi-Fi packets

I've seen similar symptoms that were due to an auto update running on the PC. The classic was Autodesk Updater. What was happening is it periodically tried to connect to the manufacturers website to see if an update had been issued.

We'd see the wifi get interrupted every minute or two as the updater took over and tried to phone home.

You can watch the Task Manager Processes list to see if anything is popping to the top every two minutes when your dropout occurs.

Re: Periodic lost Wi-Fi packets

Hi Kenton,

Team 2930 is experiencing the same problems. While we haven't had time to debug because of snow days the last couple days, I did a search on CD and found this thread from last year. Some of CD's most helpful and knowledgeable people had some insight into the problem:

Quote:

Originally Posted by Greg McCaskle

Because this is periodic, I'd open up the task manager, click on Processes and sort by the CPU column. Watch these displays together to see if something doesn't jump up at the same time as the loss starts. This is commonly caused by a SW update or a scan.

Another solution is to leave the laptop on and plugged in overnight and let it finish its background stuff so that it will leave you alone. But I prefer to turn these things off as it will come back to life in the future and cause the same issues.

Quote:

Originally Posted by Mr.Robby

We had experienced this ourself, but again it was brought back to autodesk. We un-installed Autodesk, However still experienced loss. That is because of Akamai Netsession. This program is the Downloader for Autodesk, and is the background downloader causing grief.

Look for it in your add/remove programs. Or if you want to keep autodesk, Akamai has an interface options menu. You can Disable it. That will effectively kill the net connection for Akamai and then you shouldn't experience the loss as well!

Hope this helps!

Quote:

Originally Posted by cbf

You may be getting a lot of interference on the WiFi band (presumably 2.4Ghz). Try using the inSSIDer utility to map out the WiFi sources around you.

Consider switching to the 5Ghz WiFi band (802.11ac), if your laptop supports that.

Check the bandwidth usage from your laptop using the steps found here.

Quote:

Originally Posted by Greg McKaskle

We were having bad glitches the other night and found that the AP on the robot decided to be on channel 9. The school networks are on 1, 6, and 11. That meant that the robot channel had a huge amount of retransmissions due to interference. I looked at the configuration and that indicates it should typically be on 11.

Last night, the robot was on channel 1 and everything was fine. We also learned that the team's new laptops only support 2.4 GHz. So we setup another router to bridge 5GHz so we can grab it if needed.

Based on this, I think 2930's next steps for debugging this problem will be to check for background tasks which have CPU spikes during the same time as the packet loss spikes, and try to disable any suspicious tasks. If nothing is found on this front, we will try the 5GHz connection.

Hope you find a solution to your problems! If you are successful, please post on here for the rest of us!