ISSUES 7921G roaming whit push to talk

Unanswered Question
Aug 2nd, 2012

Hello,

We have a deployment with many Cisco AP around 100,  the AP are closer each other,This AP only works with 2.4 radio, because the radio of 5 don´t have anntenas to work so the only radio to cover the deplyment is the 2.4 Ghz.

The network was designed and installed by another company, they mounted 20 Aps to cover offices and  80 Aps to cover a warehouse mounted higt around  65 feet and there are separates each other around 41 feet.

I am having issues with 7921G phones roaming through a 802.11b/g, 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, 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

This issue it´s more when use the 7921G the push to talk  ficture

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

7921G  ver 1.3.2

WLC 4400 ver 7.0.116.0

CCM ver 4.0

APs: AIR-LAP1242AG-N-K9

Thanks you

XU

I have this problem too.
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Scott Fella Thu, 08/02/2012 - 13:06

Well first off, it is suggested you go with the 1.4.(3) (fixes a lot of the roaming issues).  Second, your ap's are pretty high up there and what antennas are you using?  You also need to look at what power levels RRM is setting th access points to.  Have you used the WLC Config Analyzer.  Its a great tool that can help with some of your configurations:

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

xeum96700 Thu, 08/02/2012 - 15:53

Hi Scott,

In all the solution are used a mixed antenas AIR-ANT1728, AIR-ANT4941.

I will download the tool, and a I will let you know the result

Best regards

XU

Scott Fella Thu, 08/02/2012 - 16:05

The tool will help. You just load the two controller config and it will produce a report. Your wlc 4 failed to parse when I tied to load it. The report does how some configurations that need to be changed for

Voice 792x.

Sent from Cisco Technical Support iPhone App

xeum96700 Tue, 08/07/2012 - 11:07

Hi,

I Used the tool, but the only change it´s recomended  it´s in the 802.11a network  but this frecuency its not possible, because the 802.11a network was disabled.

I upgrade WLC firmware to the  7.0.235.0, and the data rate there are available are 9  for mandatory and the other higher data rates are supported.

The security for the phones are wep, and the multicast mode are Unicast, becuase if I configure the multicast in  Multicast mode don´t work with the PTT.

I think in the Wired LAN dont have IP multicas routing. But I cant touch the LAN network.

Best Regards

Amjad Abdullah Sat, 08/04/2012 - 00:29

I agree with Scott ( + 5 ) regarding the firmware upgrade. The firmware was a reason for many issues in the past period before it was fixed in later releases.
I just want to ask if the issue only with push to talk or with normal calls as well?

Because push-to-talk utilizes multicast, are you sure your multicast configuration on the WLC and on the wired infrastructure is correclty configured?

blakekrone Mon, 08/06/2012 - 09:21

In addition to what security what data rates are disabled, mandatory, supported? What multicast mode is the WLC set for? PTT would typically use multicast as it is simply a paging group, there has been in the past issues with certain APs and data rates set as mandatory causing multicast to fail.

migilles Mon, 08/06/2012 - 10:19

The enhancements in the scanning and roaming mechanisms in 1.4(2) or later would apply to idle (off call), on call and PTT modes.

Yes the recommended firmware is currently 1.4.3.4.

1.3(2) is light years away from present day.

Also we do not recommend to use 7.0.116.0.

There are known 1-way audio issues with the 7.0116.0 release.  Suggest to go to 7.0.235.0 today.

CAn consider 7.2.110.0 for the future, but you would need to upgrade your WLC hardware.

As for as PTT / multicast audio goes, the stream will be transmitted at the highest basic (mandatory) rate.

Per the 7925G Deployment Guide, it is recommended to have 12 (basic) and 18-24 or 18-54 as optional depending if other clients are on the same band that can take advantage of the 36-54.  No capacity or throughput advantage for a voice only application.

With 5 GHz, the default basic rates are 6,12,24, so multicast would be sent at 24 Mbps.

In the past, there were some issues wtih the 1240 sending multicast audio at 24 Mbps.

http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7925g/7_0/english/deployment/guide/7925dply.pdf

xeum96700 Tue, 08/07/2012 - 16:47

Hi,

I Used the tool, but the only change it´s recomended  it´s in the 802.11a network  but this frecuency its not possible, because the 802.11a network was disabled.

I upgrade WLC firmware to the  7.0.235.0, and the data rate there are available are 9  for mandatory and the other higher data rates are supported.

The security for the phones are wep, and the multicast mode are Unicast, becuase if I configure the multicast in  Multicast mode don´t work with the PTT.

I think in the Wired LAN dont have IP multicas routing. But I cant touch the LAN network.

Best Regards

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Posted August 2, 2012 at 12:59 PM
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