Re: voice issues with nokia phones and 1252 APs

hans.loots · ‎06-19-2008

We are running an installation with about 200 nokia dual mode phones and the ICC skinny client. We installed the first 4 floors of our building with 1131AG LAP's and a couple of 4402 WLC's.

Problems started when we installed the 5th floor with 1252 AP's. Data performance was OK, but voice problems caused a riot with my users. Strange thing is, the couple of 7921's that we use are having no problems at all. The 802.11g band, which is the busiest, is the only one having problems.

There a couple of things I already tried:

- upgrading to 4.2.130

- reducing the number of AP's to 3 per floor, so less co-channel interference problems can arise

- switching off all 802.11n support

- changed the Transmit Power Threshold to -75 dBm

At the moment I worked around the problem by replacing the 1252's with 1131's, but that leaves me with a slower network and an unsolved mystery (and a couple of dust eating 1252's)

Anyone else using a comparable setup and sharing the same problems?

Thx.

s-mvasquez · ‎06-19-2008

Hans,

We are experiencing the exact issue you are describing.

We are running WiSM controllers with the majority of 1242 AP's. We also use Ascom phones as opposed to the Nokia's.

We brought up a new wing of a building on a 3750E and 9 - 1252's and we ran into the same issue.

We tried exactly everything you did and had the same results.

The only thing we did which stabilized the phones, was to switch from UAPSD to active mode. This is not a solution however, since battery life will suffer, but it did improve stability greatly.

We currently have a TAC case open...

Hopefully there will be a solution to this soon as we have several more projects and more 1252's on the way...

wififofum · ‎06-19-2008

Hey guys,

Did you try turning off Frame Aggregation? Is there an option to change the Aggregation from A-MSDU to A-MPDU?

Check out this link describing the differences.

http://thenetworkguy.typepad.com/nau/2007/12/caveats-of-larg.html

--Bruce Johnson

hans.loots · ‎06-23-2008

Hey Bruce,

It took me a while to find (and comprehend) what you were talking about.

My WLC's are in the default setting:

802.11n Status:

A-MPDU Tx:

Priority 0............................... Disabled

Priority 1............................... Disabled

Priority 2............................... Disabled

Priority 3............................... Disabled

Priority 4............................... Disabled

Priority 5............................... Disabled

Priority 6............................... Disabled

Priority 7............................... Disabled

A-MSDU Tx ................................... Enabled

Rifs Tx ..................................... Enabled

Guard Interval .............................. Short

Too bad this setting can only be changed on the commandline and not in WCS. That's not what we had in mind when we handed Cisco the licensing fee for WCS (grmbl).

Thx,

-- Hans

wififofum · ‎06-23-2008

That's one of many commands that there's only one avenue to. I'm grumbling about how they implemented the 4.2 inter-mobility group backup controller setting (under the AP config -- why not a global setting!!). It may be centralized, but it certainly doesn't make it any simpler when its buried in a software maze.

hans.loots · ‎06-20-2008

Thx guys,

I hope I'll find some time next monday or friday to lock myself up in our testlab. I still think it's very strange that a 1252 AP with all 802.11n settings disabled behaves different than a 1131 AP.

migilles · ‎06-23-2008

Could it be due to the 2ms offshift of the beacon interval for the 1250? The beacon will come every 104ms vs the traditional 102ms. This should still be within 802.11 spec though.

Not sure if you can configure the Nokia power save mode to active when in idle and on call or not.

We do interop testing with the 7921 and AP1250 and there are no current issues there.

s-mvasquez · ‎06-24-2008

Guys,

This is what we found the issue to be. The Beacon Interval of the 1252 is running at 102ms as opposed to the recommended 100ms (even by Cisco for their 7920 and 7921 phones). I have a TAC case opened with the highest severity because the phones we are using, with UAPSD enabled, are very sensitive to this BI.

I was also told that the 1252 BI increments in 17ms, so there is no way for us to set it to 100ms. The closest is 102ms which the phones do not like at all.

The development team responded that they are aware of the issue and are working on a fix. No dates were given to me however.

migilles · ‎06-24-2008

The 7921G doesn't have any issue with the 1250 and it does use the beacons and U-APSD.

The 7920 doesn't use beacons and does not supporot power save protocols.

May need to follow up with the handset vendor for this (i.e. Nokia, Ascom, etc.).

s-mvasquez · ‎06-24-2008

Thanks for the info.

Both parties have been engaged and are working collaboratively on a solution.

The problem is now we have different types of AP's running at different BI's. Setting them all to 102ms had no effect on the situation either.

hans.loots · ‎06-24-2008

A couple of tests we did today and yesterday:

1 - I switched one 1131 AP for a 1252 in an isolated test location (no other AP within RF range). I started out with 802.11n disabled in the 2.4Ghz range as well as disabled in the 5Ghz range.

Result: voice quality OK.

2 - I enabled 802.11n in the 5Ghz range, but left it disabled in 2.4Ghz.

Result: voice quality still OK.

3 - I enabled 802.11 on 2.4Ghz.

Result: The first 30-60 seconds of a voice call start out ok, but after that the hickups begin.

I did not have time enough yet to fiddle around with the MSDU/MPDU settings or the UAPSD setting.

pasimahone · ‎06-23-2008

Hi Hans,

Which Nokia devices you have?

Could you test with E51(PR2) or E90(PR2)?

-Pasi-

hans.loots · ‎06-24-2008

We standardized on the E61i.

So it's not very easy for me to test newer S60 releases.

Regards,

-- Hans