7925g phones static/hissing and roaming issues

Answered Question
Sep 26th, 2011

Hello,

We've been having an issue for several months now with our over 200 7925g phones.  Nurses are complaining that the phones have static and will drop the voice of the other caller and several times need to repeat the conversation.  We have confirmed several scenario's.  It occurs when both callers are on 7925g inside the coverage areas in the hospital; between 7925g and 7940 desk phone; 7925g and Nortel desk phone.  We've tested on 802.11a and 802.11b/g.  I do see a difference when on 802.11b/g however still get a hissing when connecting to a different AP.

4 - 4400 controllers,  6.0.202 firmware

1 - 5508 controller, 6.0.202 firmware

234 - LAP1131AG AP's

6 - AP1131AG AP's

7 - LAP1142N AP's

3 - LAP1310G AP's

AP's are on 6.0.202.0 firmware

7925g's all are on 1.3.3 firmware but we have a select few that we are testing at both hospitals with the newest firmware 1.4.1 and still same results.

235  - 7925g phones.

We have followed the 7925g setup & deployment guide, WLC Config Analyzer and made sure all checks were made.  The only setting we plan on testing this week is changing the CCKM authentication change which was recommended.  Currently we are WPA TKIP

We have disabled the higher rates (36-54) on the 802.11a.

We also have AirMagnet VoFi analyzer which is showing issues when roaming from AP.  The alarms indicate a one-way audio issue and points to the AP's and phones power not matching.  We have our Tx power level on the controller to automatic, Max Power Level at 30 dBm, Min. at -10 dBm, power Threshold at -70 (WLC Config Analyzer recommendation).  The phone TX Power is set at 8 dBm.  Call Power Save Mode has been tested with both None and U-APDS/PS-Poll.

We have a case open with Cisco TAC and she has requested debugs from our controllers.  I have sent over 7 and she is not coming back with anything solid and not much help so far.

Our tests between 802.11a and 802.11b/g (RSSI setting on phone Auto-a and Auto-bg) have shown better with the bg mode but still static and/or hissing.

Any help would be greatly appreciated!  Thanks.

I have this problem too.
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Correct Answer by migilles about 2 years 6 months ago

Yeah I spoke to the TAC engineer that just picked up the case yesterday about next steps.

Would recommend 1.4.1.1.1.7 / 1.4(2) for any highly mobile environment (e.g. Healthcare).

FYI, 1.4(2) is due out at the end of the year.

Glad it is working out for you so far.

All of these settings sound good and what I have outlined in the 7925G Deployment Guide.

Definitely want to enable CCKM if using 802.1x.

Continuous scan mode can help with location as the phone is scanning all the time regardless of call state.

There is a small hit on battery life with continuous scan mode, but will not be significant to impact day to day operations.

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Stephen Rodriguez Mon, 09/26/2011 - 08:39

so, what does the QoS on the switches look like?  The AP ports should be trust dscp, WLC and any trunks trust cos.

If you do captures at the WLC port, are you seeing the correct QoS markings on the packet as it ingress/egress the WLC?

tfetzer Mon, 09/26/2011 - 10:35

from the debug on the controller: QoS Level........................................ Platinum 802.1P Priority Tag.............................. 6 All our AP's are on 3750 switches:  access port for all AP's is "mls qos trust dscp"; on uplink to 6513 core is "mls qos trust cos".  At core, port is configured as  "trust trust-cos"     Thanks.

migilles Mon, 09/26/2011 - 12:06

Static is typically when making calls over a trunk (PSTN connection or to a PBX).

Do you get static on IP phone to IP phone calls?

Or do you get static simply when calling to the PSTN or to a PBX?

1.3(3) is quite old now.

We are coming out with 1.4(2) at the end of the year.

Can you provide the SR # for this issue?

I can reach out to the TAC engineer.

And we can potentially provide the latest ES image to try which may help in other areas, but doubt it will resolve the static issue unless you are hitting an issue resolved between 1.3(3) and 1.4(1).

tfetzer Mon, 09/26/2011 - 12:42

We have tried all combinations of tests but mainly cisco to cisco; either 7925g to 7925g and 7925g to 7940 phones.

Our testing has been with the 7925g with the upgraded code to 1.4.1.  We've tested with both 7925g phones at this code, 802.11 modes at both Auto-a and then both at Auto-g.  Disabled the higher speeds on the controller for the 802.11a.

SR# is 619128065.  However the engineer is off now so it is being reassigned.  She is telling me that the roaming is due to the sharp turns and the "fast handoff" is not seeing the other AP right away and taking time to roam.  This is a hospital environment.  The main hospital is shaped like 2 diamonds with a hallway in the middle.  We have the AIrMagnet Survey and VoFi tools and coverage does not seem to be an issue.  However, there is a definite hissing noice and voice drop when you change AP's.

Thanks

migilles Mon, 09/26/2011 - 13:16

Thanks for the SR info.

I know the WLAN TAC engineer who is currently assigned to this SR and have asked him to post the 1.4.1.1.1.7 ES load for the 7925G phones to you.

There are scanning and roaming enhancements in this image.

But it does not include interabnd roaming support.

So as long as you don't need to roam between 5 and 2.4 GHz, then this would be a good image for you to try.

This is the base image for the 1.4(2) release, but the official version will include interband roaming support.

Please keep us posted on the results.

Thanks.

tfetzer Tue, 09/27/2011 - 06:15

The App Load ID on the phone is CP7925G-1.4.1SR1.  Is this the same as 1.4.1.1.1.7 ES?

Does anyone know if we change our authentication from WPA TKIP to CCKM if we need to reconfigure the phones or reboot? 

Thanks

migilles Tue, 09/27/2011 - 12:31

1.4.1.1.1.7 is the latest ES image.

So is not the same as 1.4(1)SR1.

1.4.1.1.1.7 does not have seamless interband roaming support.

1.4(2) will be based on 1.4.1.1.1.7 but will have seamless interband roaming.

If changing key-management or cipher type including fast roaming (CCKM), then the 792x phone will automatically sync up once the changes are complete on the WLC/AP side.

Would need to reconfigure the 792x phone only if changing the EAP type or SSID if using 802.1x authentication.

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tfetzer Tue, 09/27/2011 - 13:03

Thanks!

We finally had an awesome Cisco Engineer on our SR.  We straightened out the code and now have the correct 1.4.1.1.1.7 ES image and also configured CCKM.

We are currently testing with about 20 phones before we deploy it to over 200 phones. 

Below are the steps we took and so far the tests have resolved the issue.

1. Downloaded & installed the 1.4.1.1.1.7 code on the 7925g's.

2. Changed the Scan Mode on the device in Call Manager to 'continuous'

3. On the Controllers, configured & implemented CCKM on the voice WLAN only.

4.  Set the Radio Policy for the Voice WLAN to 802.11a only.

5.  Only using channels 36, 40, 44, 48, 149, 153, 157, 161 on 802.11a

6.  Disabled the 6,9,36,48 & 54 Mbps rates for 802.11a only

7. Configured the phone with the new voice SSID with CCKM, Security Mode as EAP-Fast, & 802.11 Mode = Auto-a.

We are following up with these test users next week so I will post if this fixes our issue.

Thanks for all the assistance everyone!

Correct Answer
migilles Tue, 09/27/2011 - 13:24

Yeah I spoke to the TAC engineer that just picked up the case yesterday about next steps.

Would recommend 1.4.1.1.1.7 / 1.4(2) for any highly mobile environment (e.g. Healthcare).

FYI, 1.4(2) is due out at the end of the year.

Glad it is working out for you so far.

All of these settings sound good and what I have outlined in the 7925G Deployment Guide.

Definitely want to enable CCKM if using 802.1x.

Continuous scan mode can help with location as the phone is scanning all the time regardless of call state.

There is a small hit on battery life with continuous scan mode, but will not be significant to impact day to day operations.

Sent from Cisco Technical Support iPhone App

tfetzer Tue, 09/27/2011 - 13:55

I actually never connected with the 2nd engineer from yesterday afternoon.  I called back today and got a 3rd engineer from NC who helped us tremendously. 

Thanks again!

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Posted September 26, 2011 at 7:56 AM
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