Channel Assignment Method automatic

[Craig Le-Butt]

Hi

I look after the wireless LAN in a hospital, several buildings 6 floors fully triangulated.

I've checked the channel Assignment, this is set to automatic, interval 12hrs.

What do other people have theirs set theirs to.

Cheers

[Scott Fella]

After it settles, 24 hours.

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[Craig Le-Butt]

Thanks for that.

If I change the CAM to 24 hours, this would scan every 24hrs from when I set?

As what I'm finding, are users logging calls, time I get there, the Channel and power could have changed from when there was an issue.

Cheers

[Scott Fella]

That is the reason I set DCA at 24 hours. I don't want the channels to change that much. After an install. I do leave it at 10 minutes and wait a day or so for the channels to settle. I baseline the channels so I know if the environment has settled. Once it does I then set it to 24 hours. I have seen client drop when the channels changed even though they are not suppose to and that's the reason I set it at 24 hours. Rather have then drop once than multiple times a day. Make the change at midnight to 5am and you should be good.

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[Craig Le-Butt]

Ive got 2 other sites which are still having the wireless extended.

In this situation when new APs installed, would you reset the CAM to 10 mins again?

Would you do this on all the controllers for that site?

Cheers

[Scott Fella]

Yes I would, but most of the time my cutovers are in the weekend so it doesn't matter. Even changing it to 4 hours or so is fine.

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[Eric Lindsey]

We have ours set at every 10 minutes. We do have clean air and event driven RRM. Would you recommend that we change it to 24 hours and just let event driven RRM handle any changes that are needed?

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[Scott Fella]

As long as all your APs are CleanAir you can. That is what I do in most of my installs.

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[Leo Laohoo]

I've set ours to 24-hours in DCA and RRM.  And after I set this, I reload the controller during midnight so the DCA and RRM happens after hours.  I can't say when low traffic happens in a hospital environment but you could look into that. 

Without CleanAir, I don't want to see channels change that it will disrupt wireless users (and blame it on "wireless").

With CleanAir, enable Event-Driven RRM (EVRRM).  This means channels will change ONLY when severe disruptions due to foreign interferrence is visible.

[George Stefanick]

Think of RRM like throwing a rock in a pond. The ripples take some time to work their way out .. I have a very large hospital system. Once it's set after 24-48 hours I turn it off ..

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[Craig Le-Butt]

Most of our APs are 1240, installed over 5 years ago, now we've started in the last 16 months adding 1140s on ward refurbishments.

Part of the reason for my original question is in our Emergency Dept, which has 1240, we're getting devices connecting to APs on the 2nd floor which are 1140s..

Also buildings are picking APs up from each other that are 30m away from each other, one building is over 200 meters away and being seen as a neighbour, from the other building, there is line of site.

[Leo Laohoo]

Part of the reason for my original question is in our Emergency Dept, which has 1240, we're getting devices connecting to APs on the 2nd floor which are 1140s..
 
Also buildings are picking APs up from each other that are 30m away from each other, one building is over 200 meters away and being seen as a neighbour, from the other building, there is line of site.

And the clients are joining 802.11b/g?

Try to disable the data rates 12 Mbps and below.  This brings down the size of your signal radius. 

[Craig Le-Butt]

Clients are both b/g and N.

That's the first thing I thought of that the N is trying to connect to 1140.

Thought of changing to 12, but we use Ekahau RFID tags, they need to connect at 5.5.

Cheers

[Eric Lindsey]

You can at least disable some of the lower data rates. Do your tags actually associate to the controllers?

We have aeroscout tags that are B radios. But they do not associate to the controller. So we left the B radio on but made the 12Mbs data rate mandatory. This pretty much killed all b clients but still allows our tags to work. But I am not sure about your tags.

Shutting down the very low data rates may help though.

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[Scott Fella]

From my experience, clients will try to connect to an 802.11n radio than just an 802.11a/b radio. The is the issue with a mixed environment as now you can't really control what APs the devices connect to. I had a client that we started building a design for and then they told us that they actually owned other buildings next to each other. Well from two blocks away at a hotel you were able to connect to their wifi. We had to bring in all the 1240's that were autonomous on some building to lwapp and also had to move lwapp APs that were associated to another WLC to the new WLC in order to have seamless roaming.

In a hospital environment and this is my opinion, I would rather cutover the whole hospital to a new wireless or new APs than doing a phased approach. This has worked well for me in the past when the client can cable new runs to each location so we can smoothly bring up the new system or APs. When the want to convert floor by floor or a wing at a time, I tell them that they better be ready for more complaints, as this will be expected.

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