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Cisco Wirelss IP phone voice quality degrades when switching from one AP (Cisco Aironet autonomous system) to another.

Hello,

We have 5 Cisco Aironet 1240 series AP's installed on site. Each AP's are operating in 2.4 GHz band and all are operating on non overlapping channels. AP1 is operating on channel 1, AP2 is operating on channel 6, AP3 is operating on channel 1, AP4 is operating on channel 11, AP5 is operating on channel 8. There is no central controller each AP is operating in Autonomous mode.

When users (Unified Wireless IP Phone 7925G) roams from one AP to other, user is not able to hear anything, sometimes calls are even dropped.  Back then it was working perfectly fine. Also the RSSI value while roaming from one AP to other is good. We also tried to scan and used the most non congested channels available (according to Cisco Aironet 1240 - channels 4 and 5 were least congested) still the calls were being dropped.

Can someone help us with this problem?

Thank you for your time in advanced.

Veeral

5 REPLIES
Cisco Employee

Re: Cisco Wirelss IP phone voice quality degrades when switching

Channel 8 is deemed overlapping as channels 6 & 11 are used.

Non-overlapping means 22 MHz of separation.

Only non-overlapping channels are supported where roaming is required.

Suggested to use 1,6,11 only to maximize the # of non-overlapping channels.

See the 7925G Deployment Guide for more info.

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

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Cisco Employee

Re: Cisco Wirelss IP phone voice quality degrades when switching

Also may want to ensure you have the recent IOS version for your AP type.

And will want to include "admit-traffic" in the SSID config even if CAC is disabled.

This was an issue with older IOS versions but resolved in recent versions.

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New Member

Re: Cisco Wirelss IP phone voice quality degrades when switching

Thank you migilles for your quick response. I understand that 8 is overlapping 6 and 11. But user cannot hear anything or sometimes calls are being dropped even if user moves from AP with channel 1 to AP with channel 6.

Also I am running IOS version 12.4 and when I looked at the running configuration and did not find "admit-traffic" in there. Should I enable it?

Do you have any more suggestion?

Again thanks a lot for your quick response.

Veeral

Cisco Employee

Re: Cisco Wirelss IP phone voice quality degrades when switching

What is the exact AP software version?

See the deployment guide that I mentioned previously for further info.

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New Member

Re: Cisco Wirelss IP phone voice quality degrades when switching

Thank you for replying back to me.

Currently I dont have access to AP directly, But I have running configuration file saved with me and it says version 12.4.

We refered to deployment guide. Do you think is it something with the Radius server which is causing delay in voice? We are using RADIUS server for authenticating users.

Thank you for your time and consideration again.

Veeral

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