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Beginner

voice Wlan issue

we have cisco 5520 wireless controller and 2 different aps : AP1852E and AP1810W

device version is 8.2.151.0 .

we have voice ssid  in the campus network

dect phones connected to voice ssid work properly inside the building without any delay or data loss during phone conversations

however , one of the floors in the building is surrounded with glass and the connection fails or conversation failures occur  when the user is on this floor

what can be the reason behind this situation

3 REPLIES 3
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Cisco Employee

Re: voice Wlan issue

It sounds as though perhaps the wireless signal between the AP and the phone is simply getting attenuated too much, perhaps by the glass.

If the AP's transmit power is much less than the phone's transmit power (typically 14dBm or so), then you can try increasing the AP transmit power and seeing if this helps.

Also, if you have lower data rates disabled (e.g. all rates below 24Mbps turned off), try enabling rates down to 6Mbps.

If you are using 5GHz, then try 2.4GHz, as the lower frequency signal propagates better.

Finally, consider placing one or two APs inside the glass room.

Hope this helps,


Aaron

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Beginner

Re: voice Wlan issue

If you are using a Cisco wireless phone you can into wireless survey mode and check how much RSSI is inside the room.

For a good coverage for VoWifi you should reach -67 dBm.

You should also consider to use only 5GHz for voice SSID for avoiding any type of interference and channel overlap.

In case that you are using 2,4GHz, as Aaron has suggested you should configure RF Profile for limiting lowest datarates.

Hope this helps

Andrea

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Beginner

Re: voice Wlan issue

i ran into this fun bug on 8.2.151 at a couple places: CSCvd64819     Cisco Wave 2 AP drops downstream DHCP; kills wcpd (reason: OOM); kernel panic


upgrade.  8.2.166 now should fix it.  My issue was that random Aps  all WLANs cease to send traffic when roamed to an AP.  It may be just most noticeable with the voice traffic in your situation.

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