Roaming problem with WLC 5508 with Phone 7921

[cmaiolani]

Hi to all,

i have one WLC with several AP1231 2.4 GHz. Everything works fine with PC and 7921 in normal condition (last firmware release 1.4.3.4).

But with 7921 there is a little problem: if i walk quicky along the warehouse and along lanes while i'm at the phone everything works well.

But the operator often have a phone call while he is on a forklift and he moves fast with this during the conversation.

In this case of fast moving, during the call, the call doesn't fall but often i do not hear 2/3 words consecutively so i can't understand the phrase.

I have already done a study of radio environment but there aren't interference, and roaming works good with walk speed, so i think that the problem is the operator's speed  in forklift (i think at the max about 10-12 Km/h)

The question is that in this case it is possible to modify parameters of Client Roaming in WLC, to reduce this issue?

If yes, somone knows what are the best values in this environment for

Hysteresis

Minimum RSSI

Transition time

Scan threshold

Or someone knows other parameters to modify or any ideas?

Thanks a lot.

[Leo Laohoo]

Cisco Unified Wireless IP Phone 7921G Deployment Guide

[cmaiolani]

Thanks a lot for replay.

I have already follow this doc for configure WLC and 7921, but i still have the same problem!

[Aaron]

The 1.4.3.4 firmware scans nicely - it will typically scan each channel every 5 seconds.

How big are your cells?  What power level are you using?  With very small cells, it is certainly possible that the forklift can drive out of and into cells faster than the phone can scan for them.

You may want to increase your cell size (increase power.)  Of course this also means that you will run the risk of co-channel interference.  In which case you may need to disable some 2.4GHz radios.

Also - be sure that your APs are placed where the forklift can hear an AP that it needs to roam to well before it has to roam to it.  For example, if the forklift is rolling straight down a corridor like this:

          |  x |            |    |

__________|    |____________|    |_____

a              >>> forklift >>>                   b

----------|    |------------|    |-----

          |    |            |  y |

then make sure that the APs that the forklift needs to use are at locations a and b, not x and y (assuming metal partitions where the lines are.)

Aaron

[migilles]

The scan frquency is not fixed.

It all depends on the # of channels discovered.

But with 1.4(2) and later, the 792x will scan at least 1 channel every second.

BTW, the 792x phone do not use the client roaming settings in the WLC as the 792x makes its own roaming decisions utilizing RSSI, beacons, and rx ACKs.