7921G roaming

[s.vosper]

Hello

I am having issues with 7921 phones roaming through a 802.11b/g/n network. The phones do not seem to be moving on to nearby APs at the right time therfore alowing the call to degrade and drop out. The network was designed and installed by another company and I am trying to optimise it to mitigate the romaing issue the customer has. I was hoping someone could give me some tips on WLC configuration and AP power to optimize the system already installed. I am really limited as to the amount and location of the APs

The WiFi network has plenty of APs installed. It certainly has -67dbm coverge in all areas and also a minimum of 20% overlap sometimes more.

7921Ga are running 1.4.1

WLCs are running 6.0.182

Thanks you

SImon

[Nicolas Darchis]

Check your config with this tool :

https://supportforums.cisco.com/docs/DOC-1373#Wireless_LAN_Controller_WLC_Config_Analyzer

It gives precious advices about setting AP powers but also QoS config for voice deployments.

I would also prefer the 6.0.202 version over the 6.0.182

[s.vosper]

Nicholas

Thank you for your responce. I have checked the configs throught the config analyser and made the recommended changes. This does not appear to have helped. I hope to change the WLC software later on today.

The issue appears to with at what point the 7921 makes the decision to roam rather than the time it takes to make the roam its self. The phone does not move to a better AP before the signal has degraded enough to cause drop outs on the call.

THanks

Simon

[weterry]

I plan to make a whitepaper or VOD on this one of these days....

In short:

Put the phone on a call

go to Status > Neighbor List

Walk around and look at the Neighbor List

If at any point in time the AP you want to roam to is NOT in that list when you think it should be, that is why you're hanging on to the other AP too long.   

This is not usually a scenario where the phone hangs on to an AP too long, but instead the correct AP to roam to hasn't been discovered yet....

Either way, definitely need something newer than 6.0.182.0.

And you might consider trying like a 1.3.2 or 1.3.3 on the phone and see if the same behavior happens (and call TAC with the results).

Other than that, phone traces can be collected that will tell you why the phone is and isn't roaming....

[s.vosper]

Thanks for the advice on the firmware\software, i will try changing these.

How do you go to the neighbour list when i a call?

Can you point me in the direction of instruction to take phone traces?

THanks you

Simon

[s.vosper]

Forgive my hasty response i have discovered how to bring up the neighbors screen whilst in a call. Strangely the roaming appears to work far better when I am viewing the neighbour list whilst in a call!

[weterry]

Well I'm pretty sure there isn't a "feature" for that

Although, and I am being serious here, maybe the attentuation of your head when the phone is up to your ear is having an impact.   You'd be surprise how walking down the hall with the phone on your left ear could completely change characteristics than with it on your right ear......  (but it still all depends on AP placement, scan time, coverage, etc..)

[s.vosper]

Looking at the neighbour list while in a call has provided us with some good insight into which access points are available.

We are still seeing occassions where we are moving into areas where we should have strong signals from multiple nearby APs but they are not populating the neighbour list until long after the call has started to degrade because the associated AP signal has become too weak if they do at all. These APs are seen when viewed through the site survey. It seems like the phone is not picking up the APs it needs to roam to. The APs are placed to ensure a good over lap. I dont understand why APs that are so close by are not being discovered

We have upgrade the controllers to 6.0.202 this evening but to no avail.

ANy thoughts on what this might be are welcome as we have been beating our heads against a wall with this all week.

Many thanks for your responces so far.

Regards

Simon

[weterry]

My suggestion is that you open a TAC Case against the phone (regarding wireless connectivity of the phone) and you explain exactly what you just said.

But... if possible, you might want to try seeing how 1.3.3 behaves on the same phone compared to 1.4.1....

[robvreede]

Hi,

we were experiencing the same issues.

The VoWifi design guides (i.e. TPC, DCA, Media, EDCA, WMM, QoS) have been followed setting up the Controllers.

Tested WLC4402 / WLC4404 with firmware versions 4.2.207 and 7.0.116.

Experiencing the issues on 7921G (firmware 1.3.4SR1) and 7925G phones (firmware 1.3.4SR2 and 1.4.1SR1).

The access points used are 1242G with a mix of AIR-ANT1728 and AIR-ANT24020V-R diversity antennas.

It is a warehouse environment. Phones are very near to access points.

We only use 802.11b/g for wireless phones and data clients.

The only issue I found is the cell size which is small and AP transmit power is low.

Auto RF and Auto DCA is enabled. AP power levels are 5, 6 or even 7 in areas with a lot of access points.

We have a high density b/g clients on some areas in the warehouse and added some access points to seperate the AP load

going back to version v1.3.3 was the solution for us.

The new inter band roaming algorithm might be causing the Voice issues.

We do not use the 802.11a radios (available, but disabled).

Even configuring b/g on the 792x phone did not stop it from scanning the 802.11a band.

Reference:

http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7925g/firmware/1_3_4/english/release/notes/792x_134.html#wp240885

Kind Regards,

Rob Vreede.

[Frank Hoeben]

Jumping on the bandwagon.

We're having the same problems with any firmware other than 1.3(3).

The solution would be to down/upgrade all devices to this firmware, but alas, the newer hardware revisions of the 7921G fail to load any older firmware than the 1.4 series and the factory default firmware is so buggy it starts roaming to a far away AP all by itself even if you're standing right next to the AP.

The 1.4(2) seems to be slightly better than earlier 1.4 firmwares but is far from perfect.

The 7925G model doesn't display this erratic roaming behavior at all.

[migilles]

Yes the latest 7921 versions require ES 1.3.3.0.3, 1.3(4) or later.

1.3(4) has seamless interband roaming support though and the scanning was re-worked a bit in that release.

There were further enhancements in the 1.4(2) release that came out towards the end of last year, which can benefit in environments with pico cells, where an AP signal can be held only for less than a few seconds, etc.

So your issue is that the 7921 phones are not roaming to an AP (what you think is the best candiadte at the time) in a timely fashion?

But the 7925s running 1.4(2) roam fine?

Are the issues specific to a certain area or trying to roam to a particular channel?

If you want the 1.3.3.0.3 ES, just open a TAC case and request it.

However, we would recommend to use 1.4(2), which has been proven to be very successful for many customer deployments.

I am curious if you are using a Cisco WLAN solution or a 3rd party WLAN solution?

If Cisco, what is the WLC/AP platform and version?

Either way, would suggest to open a TAC case to troubleshoot this further.

[migilles]

1.4(2) will have more aggressive scanning.

If 1.3(3) works better than 1.3(4) or 1.4(1), then open a TAC case and may be able to provide some dev phone code.

Sent from Cisco Technical Support iPhone App

[Justin Kurynny]

Simon,

Did you ever get a chance to get these phones onto 1.4.2? I am running into the exact same issue and will move toward getting my client's phones upgraded ASAP. Just wondering if you ever got this issue ironed out.

Justin

[ROBERT T]

I am using the 7921G on the A band and I get the same thing.

The biggest things I have found to get roaming to work well is the following.

1. Setup the phones to only scan the channels that you are using.

2. Line of site to AP's is very important in drive or walk aisles.

3. I have not noticed a difference between 1.3(x) and 1.4.2, doesn't meant it wouldn't work better for you.

4. Lower your AP's where ever you can. If above a drop ceiling, lower them below.

5. Make sure roaming is correctly enabled on your controllers. I found that two of my three controllers were not correctly configured.

6. I use 8 channels and have all of the AP's on full power due to the environment.

You can view a list of things that I have done to improve roaming at my forum.