Cisco 8821 audio issues

[G3261]

Hello, we have been struggling with voice quality and roaming issues with Cisco 8821 phones for some time now. I understand the recommendations are 5Ghz for these models to work properly but we are unable to move to 5Ghz and still using 2.4Ghz. Initially, we have had lot of issues but over the time they got better. However, now, we are back to problems again. Majority of user calls now is about 'distorted voice', 'silence', 'unable to hear callers or callers can not hear them' and things are bad when clients are roaming!!!

Last few days, I have been collecting logs on specific MAC of the phones and I also have UCM phone logs. However, I am not too sure what exactly I need look for voice quality issues!!!

If someone can guide me , I would really appreciate it.

UCM 11.5

wlc 5508

phones are running latest ver of the firmware

I don't have any support available from Cisco.

[Leo Laohoo]

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@G3261 wrote:

Majority of user calls now is about 'distorted voice', 'silence', 'unable to hear callers or callers can not hear them' and things are bad when clients are roaming!!!

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I have already addressed the issue with 2.4 Ghz and voice limitation in your previous thread (LINK).

Please provide more information: 

1. Exact firmware of the 8821
2. Exact firmware of the WLC
3. What AP models used

[G3261]

Thanks for looking into this Leo and I do understand 5Ghz will be better for phones to work properly.

sip8821.11-0-4-14

-Phone

8.5.151.0-WLC

APs are---2800, 3700 (majority) and 3800

[Leo Laohoo]

Are you able to determine if this problem is common across all the AP models?  I want to know if this issue is more common on the 2800/3800 and never on the 3700. 

If this problem is common in 2800/3800 then try turn off WMM and MU-MIMO to the voice SSID. 

[G3261]

so far...problem seems to be on 3502 and 3602 model of APs. I asked users to call me once they have issues. I received 4 calls total and all 4 are these models. Should I still try to find and change WMM and Mu-MIMO?

[Leo Laohoo]

Turn off MU-MIMO and anything related to 802.11ax.

[G3261]

Thanks Leo…it seems to me all the problems are   Related QoS with these phones…. More specifically when users are roaming!!!  Should I still consider turning off MU-MIMO? Would this effect any other WL devices like 7925s?

[Leo Laohoo]

MU-MIMO is just another part of 802.11ac. 

7925G and 8821 only understand MIMO.  I really do not see any benefit of enabling MU-MIMO with voice traffic.  

Be aware that 8821, regardless of whatever firmware is really a "difficult" piece of hardware and it is about to be replaced (if one can actually afford the replacement) by the Cisco Webex 840/860.

Cisco 840/860 is a rebadge of the Spectralink 95/96.  Take note that the Spectralink 95/96 is just an Android-based "mini-tablet" with a SIP application to do the calls.  Cisco 840/860 is no different and uses WebEx to make the calls.  

We have a growing fleet of Spectralink 96 phones.  A few years ago, I did a side-by-side test between the Spectralink 96 and 8821 and I found Spectralink phone was able to detect the SSID a lot faster and were also better in roaming.

[G3261]

really a "difficult" piece of hardware-----AGREED....as a replacement for 7925s, this is still a nightmare unless you are running latest/greatest WLC and 5Ghz. Lot of places are unable to make that investment to move to 5Ghz and change WLCs hardware, APs, switches!!! I am hoping these new models... 840 (more specifically) will give us some break and work better than 8821!!! Yes, they are double the price.

Much appreciated your input in this topic over the last few years. Most of the problems we have been facing related to 'silence' (when on a call), one way communication, choppy (distorted) voice!!! I will take a look into above settings you mentioned. Thanks

[G3261]

Leo, there is MU-MIMO setting on WLC, I am assuming you are suggesting to uncheck that box...is there similar setting on Cisco AP as well?

[Leo Laohoo]

WLAN > SSID > Advanced tab. 

There are a number of MU-MIMO boxes that are, by default, enabled.  Untick those. 

In the front, there should be an 802.11ax box at the bottom of that page.  Untick that.  

[G3261]

Yes… I saw these settings at exact location. Thanks 

Is there a Cisco document which says that 7925 and 8821 phones do not use this technology? I tried to find it!!!