Dealing with wireless interference from cellphones

[John Sabath]

We had a high-school assembly today in front of ~1400 people. We tested before hand (in the same venue, just without all the people) and we had no problems.

However, once it filled up, we encountered ridiculous amounts of lag in the communications; rendering the bots unsafe to drive around.

Have any teams had experience with presenting in front of a large group like this? Did you have to buy an external antennae for the driver station?

[Phalanx]

The question that needs to be asked is at what frequency band where you operating your DLINK and Driver Station at?

1) If you are using the 2.4ghz frequency, then yes, it's highly likely there was lots of interference from all the cells phones in the room, also broadcasting in the 2.4ghz range.

2) Does the school also have wireless? The schools wireless AP's could also be broadcasting in the 2.4ghz band. Again that creates even more "noise".

So all the cell phones and schools network are creating so much wireless noise your D-Link and Driver Station can't maintain a clean, reliable signal.

If your driver station and dlink are using the 5ghz frequency then you shouldn't have been impacted to that extent.
IIRC there are not that many cells phones that operate in the 5ghz band.

Lastly, having a 25 or 50 foot Ethernet cable available to be tethered instead of wireless can be helpful for such demos.

[pyroslev]

1400 people with who knows how many on wifi could give you headaches. With FTC, we make announcements periodically asking people to turn of Wi-Fi on phones.

Did you ask the venue to turn off unsecured wireless networks or disable internet access to them?

And it's possible there was a lot of non-WiFi related interference. That can have you beating your head against a wall for hours.

[sanddrag]

We've had this exact scenario happen to us twice at graduation and I don't have a solution yet. Robot tested in the venue with no problems whatsoever, excellent communication over 150 ft range. As soon as 800 or so people show up, we're dropping packets like crazy and can barely even operate the thing, even at closer (<50ft) range. Operating direct from the Classmate PC.

[John Sabath]

Originally Posted by Phalanx

The question that needs to be asked is at what frequency band where you operating your DLINK and Driver Station at?

1) If you are using the 2.4ghz frequency, then yes, it's highly likely there was lots of interference from all the cells phones in the room, also broadcasting in the 2.4ghz range.

2) Does the school also have wireless? The schools wireless AP's could also be broadcasting in the 2.4ghz band. Again that creates even more "noise".

1) I bet it is on 2.4ghz now that I think about it.
2) And yes, it does, they have 2 AP's in the gym alone.

Thanks for the heads-up about the 2.4ghz band, I'll make sure we keep in on 5ghz from now on.

[Tommy F.]

Originally Posted by John Sabath

Thanks for the heads-up about the 2.4ghz band, I'll make sure we keep in on 5ghz from now on.

If you guys are using the classmate, it only recognizes a 2.4ghz signal. So you will have to use a different computer as the driver station if you're not doing so already.

[plnyyanks]

Originally Posted by 7h0m54

If you guys are using the classmate, it only recognizes a 2.4ghz signal. So you will have to use a different computer as the driver station if you're not doing so already.

Of, if you have another router than's capable of using the 5ghz band, you can plug that into the Classmate. A nicer router will probably get better reception than the Classmate's card, anyways.

[John Sabath]

Originally Posted by plnyyanks

Of, if you have another router than's capable of using the 5ghz band, you can plug that into the Classmate. A nicer router will probably get better reception than the Classmate's card, anyways.

That's what I was thinking about doing; just rigging up a tower similar to what is used at competition. We should have a few spare routers laying around.

[FrankJ]

As others have said. Use the 5g band. Use an encrypted SSID to keep the curious from connecting. Remember that you will have to set one of your routers to bridge mode (assuming your computer doesn't have a 5g radio).

We use the one of the old brown bridges from breakaway plugged into the lap top with the AP on the robot.

[DCA Fan]

I've seen this problem at demos and off-seasons. Yes, you definitely need to switch over to the 5ghz band, it'll be a lot less crowded. At 2.4ghz you have to contend with most school wifi, almost all cell phone mobile hotspots.

[Bryce Paputa]

We had this issue with our first pitch at Comerica Park, we ended up just using an ethernet tether.