[Greg McKaskle]

I attend a good number of FIRST events, and I have a few tools that I use to look at the wifi spectrum. I've attached a few screenshots from Michigan State Champs last year.

The first is a bit fuzzy, but shows that on the campus, there were lots of other access points. Venues differ ALOT, and some are wifi-crowded. The field doesn't show up because it doesn't broadcast its SSIDs.

The second photo is the wifi usage on the channel(s) that the field was using. It is shown three ways. The lower one is total packets per second for each 100ms period. The middle one shows bytes transmitted per second. The top shows airtime being used, and is on top because this is the best indication of how much more you can transmit before you hit the ceiling.

The stacked colored bands are the traffic caused by each robot, and the external stuff is gray. There is a white line plotted over the rest that is the retransmissions.

To summarize what this says ... The robots in these matches were typically using 10% of the wifi spectrum. The spikes due to a radio momentarily shifting to slower speeds caused a momentary spike to 25%. If this had hit the ceiling and caused other radios to slow, it would have been a Xmas tree event. I logged the entire weekend and never saw a tree.

Another factoid? There were 1217 unique MAC addresses that showed up on the 5GHz wifi channel on Saturday -- a few of those are even robots. But most of those devices are simply looking to see what wifi networks are available. They build the list and go dormant again.

I have never been at an event where wifi was stressed to its limits. I have heard stories, and I believe it has happened. I do not believe it is common, and FIRST is diligent at using the wifi that is available to run the best matches possible.

By the way, I have also seen matches where individual robots are sending 20Mbps HD video. The sky didn't fall. The team was asked to change camera settings. No big deal. The wouldn't be nearly as simple without usage guidelines.

I'm not claiming that things can't be made better, but before we try to fix the problem, we need to measure quantitatively what is actually going on.

As for the original topic. The field controls whether robots can communicate with each other over its AP. It cannot happen without the field specifically allowing it and coordinating it.

Greg McKaskle