Voice Quality Monitoring - Cisco 7925G Administration Manual

Troubleshooting
Solution
For troubleshooting information, see the Cisco Unified Wireless IP Phone 7925 and 7926 Series Deployment
Guide.

Voice Quality Monitoring

To measure the voice quality of calls that are sent and received within the network, Cisco IP Phones use the
following statistical metrics that are based on concealment events. The DSP plays concealment frames to
mask frame loss in the voice packet stream.
Concealment Ratio metrics
Concealed Second metrics
MOS-LQK metrics
Note Concealment ratio and concealment seconds are primary measurements based on frame loss while MOS
LQK scores project a "human-weighted" version of the same information on a scale from 5 (excellent) to
1 (bad) for measuring listening quality.
Listening quality scores (MOS LQK) relate to the clarity or sound of the received voice signal. Conversational
quality scores (MOS CQ such as G.107) include impairment factors, such as delay, that degrade the natural
flow of conversation.
For information about configuring voice quality metrics for phones, see the phone metrics sections in the
Cisco Unified Communications Manager documents.
You can access voice quality metrics on the phone or remotely by using Streaming Statistics.
Related Topics
Remote Monitoring, on page 195
Shows the ratio of concealment frames over total speech frames. An interval conceal ratio is calculated
every 3 seconds.
Shows 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 5 percent concealment frames.
Uses a numeric score to estimate the relative voice listening quality. The 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.
Cisco Unified Wireless IP Phone 7925G, 7925G-EX, and 7926G Administration Guide
Voice Quality Monitoring
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