Voice Quality Troubleshooting Tips - Cisco 7941G Administration Manual

Troubleshooting and Maintenance
The following codecs on the Cisco Unified IP Phones 7962G and 7942G provide these maximum MOS LQK
scores under normal conditions with zero frame loss:
• G.711 gives 4.5
• G.722 gives 4.5
• G.728/iLBC gives 3.9
• G.729 A/AB gives 3.8
The following codecs on the Cisco Unified IP Phones 7961G/G-GE and 7941G/G-GE provide these maximum
MOS LQK scores under normal conditions with zero frame loss:
• G.711 codec gives 4.5 score
• G.729A/ AB gives 3.7
• CVTQ does not support wideband (7 kHz) speech codecs, because ITU has not defined the extension
Note
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.
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:
Table 52: Changes to Voice Quality Metrics
Metric change
MOS LQK scores decrease
significantly
Condition
Network impairment from packet loss or high jitter:
• Average MOS LQK decreases could indicate widespread and uniform
• Individual MOS LQK decreases indicate bursty impairment.
Cross-check with Conceal Ratio and Conceal Seconds for evidence of packet
loss and jitter.
Cisco Unified IP Phone 7941G, 7941G-GE, 7942G, 7961G, 7961G-GE, and 7962G Administration Guide for Cisco Unified
impairment.
Communications Manager 9.0 (SCCP and SIP)
Voice Quality Monitoring
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