Using Voice Quality Metrics; Troubleshooting Tips - Cisco CP-7970G Administration Manual

Monitoring the Voice Quality of Calls

Using Voice Quality Metrics

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:
•
•
Note •
•
•
A Conceal Ratio of zero indicates that the IP network is delivering frames and packets on time with no
loss.

Troubleshooting Tips

When you observe significant and persistent changes to metrics, use
troubleshooting information:
Cisco Unified IP Phone Administration Guide for Cisco Unified Communications Manager 8.5
9-18
For Cisco Unified Phones 7975G, 7965G, and 7945G:
G.711 gives 4.5 score
–
G.722 gives 4.5
–
G.728/iLBC gives 3.9
–
G.729A/AB gives 3.8
–
For Cisco Unified Phones 7971G-GE and 7970G:
– G.711 codec gives 4.5 score
– G.729A/AB gives 3.7
CVTQ does not support wideband (7 kHz) speech codecs, as ITU has not defined the extension of
the 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.
Reporting G.711-scale MOS scores for wideband calls through the use of CVTQ allows basic
quality 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.
Unlike MOS, the Conceal Ratio and Concealed Seconds metrics remain valid and useful for both
wideband and narrowband calls.
Chapter 9 Troubleshooting and Maintenance
Table 9-5 for general
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