Cisco 7971G-GE - IP Phone VoIP Dépannage et maintenance - Page 23
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Troubleshooting and Maintenance
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 (see
Call Statistics
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. The following codecs
provide these maximum MOS LQK scores under normal conditions with zero frame loss:
• For Cisco Unified Phone 7975G, 7965G, and 7945G:
• For Cisco Unified Phone 7971G-GE and 7970G:
Note
• CVTQ does not support wideband (7 kHz) speech codecs, as ITU has not defined the extension of the
• Reporting G.711-scale MOS scores for wideband calls through the use of CVTQ allows basic quality
• Unlike MOS, the Conceal Ratio and Concealed Seconds metrics remain valid and useful for both wideband
A Conceal Ratio of zero indicates that the IP network is delivering frames and packets on time with no loss.
Voice Quality Troubleshooting Tips
When you observe significant and persistent changes to metrics, use the following table for general
troubleshooting information:
Screen) or remotely by using Streaming Statistics (see
• G.711 gives 4.5 score.
• G.722 gives 4.5.
• G.728/iLBC gives 3.9.
• G.729A/AB gives 3.8.
• G.711 codec gives 4.5 score.
• G.729A/AB gives 3.7.
technique to wideband. Therefore, MOS scores that correspond to G.711 performance are reported for
G.722 calls to allow basic quality monitoring, rather than not reporting an MOS score.
classifications to be indicated as good/normal or bad/abnormal. Calls with high scores (approximately
4.5) indicate high quality/low packet loss, and lower scores (approximately 3.5) indicate low quality/high
packet loss.
and narrowband calls.
Voice Quality Metric Interpretation
Remote
Monitoring).
Troubleshooting and Maintenance
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