Roaming decision and issue.

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Sep 3rd, 2009
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I have 2 AP's that I seem to be having somekind of issue with. I can be associated to one AP and as I move close to the other, I never change association. I can be stand 5 feet from this AP and still not associate to it. If I disable and re-enable my wireless card then I can reassociate to the AP I would expect to be on. I have been told that the wireless client on my laptop is where the decision to roam from AP to AP is made. How true is this statement? Second, I run WLC 4402's with 1252 AP's. What parameters in the controller can be modified to force a client to move to the AP with better RSSI.

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dancampb Thu, 09/03/2009 - 08:44
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Deciding when and where to roam is a client based decision as per the specs. Most likely when you move closer to the other AP you still haven't hit the minimums for the client to start scanning for another AP to roam to. One way you could try to coax the roam is move closer to the other AP, then change the tx power level on the original AP to the lowest setting.

v-linder Thu, 09/03/2009 - 12:20
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Thank you for the reply. I have been adjusting the power settings and that seems to have helped to some degree. I am going to continue this approach. It seems to me that the Dynamic Power Control adjustments are not functioning as I would expect them to. I have 2 AP's about 25 to 30 feet apart and when I leave the power settings to global, it adjusts power to full strength.

weterry Thu, 09/03/2009 - 19:49
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I believe the algorithm for TPC requires 3 APs to hear this particular AP at a specific threshold. So, if you only have two APs, no matter how close you put them, it isn't enough to scale down the power.

One test you could do is look at what RSSI your client has when you are expecting it to roam. If you are still better than -65 (or around there), you probably haven't reached the clients threshold.

The fact that your APs are 25 to 30 feet apart, if they are truely at power level 1, it may not be unreasonable to have get 10-20 feet past this 2nd for your client to roam.

Bottom line, client chooss when to roam.

v-linder Fri, 09/04/2009 - 05:19
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It appears that this in fact may be the case. It takes about 10 to 15 feet past the second AP before my client will roam to the next AP. I agree the power is not the only factor even though it did help to a certain degree. I am considering removing one of the AP's. I may be to dense in this area.

lorinzo2002 Thu, 09/03/2009 - 12:21
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your saying there is a setting on the client to force it to hop to the next ap? I am having this same issue. I have 4 ap's, all same ssid, encryption..etc, 1 is set as parent, the other 3 are repeaters. I have run wireless signal strength tests, and my laptop will not switch to next ap untill signal strength drops to 20%. even if i'm standing directly next to repeater ap. any suggestions?

v-linder Thu, 09/03/2009 - 12:27
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Every wireless card is different so I'm not sure if there is or not. I was hoping that there would be a way that the controller could tell a client to start looking for a better RSSI after a certain threshold. However, I am having trouble similar to yours in that my clients don't want to let go of what they are associated to even though I know for a fact that there is a better RSSI say..... 15 feet away for example.

Gary Smith Fri, 09/04/2009 - 00:47
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There are a few things worth considering asnd playing with. How far apart are the access points? What power settings (cell size)? Data rates allowed? These varibles could improve/worsen the situation. Without knowing exactly the set up you have, I would suggest playing around with these varibles.

v-linder Fri, 09/04/2009 - 06:48
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Thank you for the reply. I am actually in the process of doing exactly that. I will let you all know what the results are.


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