Voice Quality Monitoring; Voice Quality Metric Interpretation - Cisco 7941G Administration Manual
For cisco unified communications manager 9.0 (sccp and sip)
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Also See for 7941G:
- Administration manual (302 pages) ,
- User manual (132 pages) ,
- Phone manual (92 pages)
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Voice Quality Monitoring
Voice Quality Monitoring
To measure the voice quality of calls that are sent and received within the network, Cisco Unified 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: Shows the ratio of concealment frames over total speech frames. The phone
• Concealed Second metrics: Shows the number of seconds in which the DSP plays concealment frames
• MOS-LQK metrics: Uses a numeric score to estimate the relative voice listening quality. The Cisco
Concealment ratio and concealment seconds are primary measurements based on frame loss while MOS
Note
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.
You can access voice quality metrics from the Cisco Unified IP Phone by using the Call Statistics screen or
remotely by using Streaming Statistics.
Related Topics
Call Statistics Screen, on page 184
Remote Monitoring, on page 191
Voice Quality Metric Interpretation
To use the metrics for monitoring voice quality, note the typical scores under normal conditions of zero packet
loss and use the metrics as a baseline for comparison.
It is important to distinguish significant changes from random changes in metrics. Significant changes are
scores that change about 0.2 MOS or greater and persist in calls that last longer than 30 seconds. Conceal
Ratio changes should indicate greater than 3 percent frame loss.
MOS LQK scores can vary based on the codec that the Cisco Unified IP Phone uses.
Cisco Unified IP Phone 7941G, 7941G-GE, 7942G, 7961G, 7961G-GE, and 7962G Administration Guide for Cisco
Unified Communications Manager 9.0 (SCCP and SIP)
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calculates an interval conceal ratio every 3 seconds.
due to lost frames. A severely "concealed second" is a second in which the DSP plays more than five
percent concealment frames.
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.
The phone uses the Cisco proprietary algorithm, Cisco Voice Transmission Quality (CVTQ) index, to
produce MOS LQK scores. 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.
Troubleshooting and Maintenance
- Quick Links:
- Cisco Unified Ip Phone 7942G
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Troubleshooting
