Monitoring The Voice Quality Of Calls - Cisco 7925G - Unified Wireless IP Phone VoIP Administration Manual

Resolving Voice Quality and Roaming
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Phone Does Not Roam Back to Preferred Band
When the Cisco Unified IP Phone 7960 is set to 5 GHz band as the preferred network and is
authenticated to an AP on that band and roams to an area in which 5 GHz is not longer available but 2.4
GHz is available, the phone operates. But if you roam back to the 5 GHz band area, the phone will not
return to the 5GHz band.
Since the phone will only switch between bands when connectivity has been lost, you must reboot the
phone to return to the preferred band of 5 GHz.
Related Topics
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Monitoring the Voice Quality of Calls

To measure the voice quality of calls that are sent and received within the network, Cisco Unified IP
Phones use these statistical metrics that are based on concealment events. The DSP plays concealment
frames to mask frame loss in the voice packet stream.
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Cisco Unified Wireless IP Phone 7925G Administration Guide for Cisco Unified Communications Manager 7.0(1)
10-12
There might be an authentication type mismatch between the phone and the next access point.
The access point might be in a different subnet from the previous access point. The Cisco Unified
Wireless IP Phone 7925G is capable of Layer 2 roaming only. Layer 3 roaming requires WLSM that
uses GRE. For more information, see
If using EAP-FAST, LEAP, or Auto (AKM) authentication, the access point might be using filters
to block TCP ports. The ACS server uses port 1645 for authentication and 1646 for accounting and
the RADIUS server uses port 1812 for authentication and 1813 for accounting.
Resolving Startup and Connectivity Problems, page 10-1
Resolving Voice Quality and Roaming, page 10-8
General Troubleshooting Information, page 10-14
Monitoring the Voice Quality of Calls, page 10-12
Concealment Ratio metrics—Show the ratio of concealment frames over total speech frames. An
interval conceal ratio is calculated every 3 seconds.
Concealed Second metrics—Show the number of seconds in which the DSP plays concealment
frames due to lost frames. A severely "concealed second" is a second in which the DSP plays more
than five percent concealment frames.
MOS-LQK metrics—Use a numeric score to estimate the relative voice listening quality. The
Cisco Unified IP Phone calculates the mean opinion score (MOS) for listening quality (LQK) based
audible concealment events due to frame loss in the preceding 8 seconds, and includes perceptual
weighting factors such as codec type and frame size.
MOS LQK scores are produced by a Cisco proprietary algorithm, Cisco Voice Transmission Quality
(CVTQ) index. Depending on the MOS LQK version number, these scores might be compliant with
the International Telecommunications Union (ITU) standard P.564. This standard defines
evaluation methods and performance accuracy targets that predict listening quality scores based on
observation of actual network impairment.
Chapter 10 Troubleshooting the Cisco Unified Wireless IP Phone 7925G
"WLANs and Roaming" section on page 2-7.
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