Using non KOP router, possible cause of wireless communication issues?

[saba]

Hi,

Team 611 has been using a WRT54G router instead of the one provided in the KOP (somebody took the one we got in last year's KOP, so I brought an old router from home). Because this router doesn't support wireless-n, we have both the bridge and the router set up to be as compatible as possible. I think I remember it working fine in my basement, but it has been performing abysmally at school. After looking through other posts, I am suspicious that perhaps it is the school network interfering with our wireless communications. I was wondering if someone could explain what is going on and perhaps explain why.

thanks,

~saba
Team 611

[JBotAlan]

To state the obvious: you probably should obtain a new KOP router. The part is a Linksys WRT160N, available for $99 (or, for a limited time, $75, from Newegg; I personally strongly suggest ordering from them, as their shipping is FAST).

To say any more would be speculation; it is possible that another network is interfering.

Something else to check: I seem to remember there being an issue with sticking your router up against a metal member of your robot. If you move it a little further away from the frame, does it perform better?

[Radical Pi]

If it is only a problem at school, I would recommend changing the broadcast channel of the router.

[Isaac501]

Find out what networks are strong where the team practices. The networks will be on channels 1/6/11 (if the school IT people have any clue what they're doing). Pick another channel, preferably as far from (in channel number) from the networks present.

[Nadav Zingerman]

As an Israeli team, where 5GHz (the frequency 802.11n uses) is an illegal military frequency, we are forced to use non-KOP routers and wireless bridges. We operate in an environment with at least two Wi-Fi network with large ranges and broadcast power.

We have experienced no problems with any of the wireless gear, despite using cheap generic equipment. The cRIO and WPILib should have no problem using different equipment, nor should they be aware of the change.

When you say the network performs bysmally, what do you mean? Does it connect? Does it lose connection? Is there significant delay in communication?

[saba]

Well, the connection to the robot is often lost and then regained, we can't drive it for more than a couple seconds at a time when we get the connection without losing it again, and there is often a delay in the communications.

[Alan Anderson]

Originally Posted by saba

Well, the connection to the robot is often lost and then regained, we can't drive it for more than a couple seconds at a time when we get the connection without losing it again, and there is often a delay in the communications.

Hang on a second. When you lose the connection, is it typically right after you start driving? It might be a battery voltage issue. Where do you have your WGA power connected? It might also be interference from motors and/or speed controllers. Where do you have your WGA mounted?

[EricVanWyk]

Originally Posted by Alan Anderson

Hang on a second. When you lose the connection, is it typically right after you start driving? It might be a battery voltage issue. Where do you have your WGA power connected? It might also be interference from motors and/or speed controllers. Where do you have your WGA mounted?

Quoted for Truth.




Also, we use a WRT54G with out issue.

[Racer26]

Originally Posted by Nadav Zingerman

As an Israeli team, where 5GHz (the frequency 802.11n uses) is an illegal military frequency, we are forced to use non-KOP routers and wireless bridges. We operate in an environment with at least two Wi-Fi network with large ranges and broadcast power.

We have experienced no problems with any of the wireless gear, despite using cheap generic equipment. The cRIO and WPILib should have no problem using different equipment, nor should they be aware of the change.

When you say the network performs bysmally, what do you mean? Does it connect? Does it lose connection? Is there significant delay in communication?

I didn't know this... does FIRST do something special for the Israeli Regional as far as FMS and the onboard bridges? Or do they get special clearance from the Israeli Military?

[saba]

http://mankindisone.com:8000/2010-01-19 17.59.55

there's a link to an image of our robot's electronics from week 1. most of the stuff in the picture has done some moving since then, but the crio, wga, power distribution board and jaguars haven't moved much. Now that you mention it, battery was low at the time. I should charge batteries more and see how it goes.

[Doc Wu]

Originally Posted by Isaac501

Find out what networks are strong where the team practices. The networks will be on channels 1/6/11 (if the school IT people have any clue what they're doing). Pick another channel, preferably as far from (in channel number) from the networks present.

The reason they pick 1/6/11 is because of the way spread-spectrum radio works. The channel specified is the "home" frequency. The actual signal hops from frequency to frequency very rapidly across a range of several channels. It follows a known pattern, so the receiving unit can follow along.

The reason they pick channels 1/6/11 is that those are separated enough that they won't overlap and are always clear to each other. A unit on channel 1 won't reach up to the lower limit of one on channel 6, for example.

Putting another unit on in the 2-5 range at a distance where it is far enough away from the channel 1 or 6 unit will work, but if it is in close proximity, they will still overlap and interfere with each other.

In a school or other building where they want to saturate it with multiple access points, they will stagger them so if one unit is on channel 1, the next closest is on 6, then the next is on 11, then back to 1. If they are a couple hundred feet apart, by the time you get another channel 1, it is 600-1000 feet away from the first.

But if your router is right near a strong access point, you might receive interference on several channels. If you are between access points on all three channels, you might not be able find a channel that is clear.

But chances are you are only primarily being bothered by one and careful selection of the channel manually may help. Using a sniffing tool (Google Wardriving, or Netstumbler) might help you find out what is happening. I have also seen router firmware that shows you what "Neighbor" nodes it is hearing and the channels they are on.

Or, get a Type-N router...