Cisco 8831 Administration Manual page 149

Troubleshooting and maintenance
MOS LQK scores can vary based on the codec that the conference phone uses. The following codecs provide
these maximum MOS LQK scores under normal conditions with zero frame loss:
• G.711 codec gives 4.5 score
• G.719A/ AB gives 3.7 score
A Conceal Ratio of zero indicates that the IP network is delivering frames and packets on time with no loss.
When you observe significant and persistent changes to metrics, use the following table for general
troubleshooting information.
Table 35: Changes to Voice Quality Metrics
Metric Change
MOS LQK scores decrease significantly
MOS LQK scores decrease significantly
Conceal Ratio and Conceal Seconds increase
significantly
Conceal Ratio is near or at zero, but the voice quality
is poor
Voice quality metrics do not account for noise or distortion, only frame loss.
Note
Cisco Unified IP Conference Phone 8831 Administration Guide for Cisco Unified Communications Manager 9.0
Voice quality monitoring
Condition
Network impairment from packet loss or high jitter:
• Average MOS LQK decreases could indicate
widespread and uniform impairment.
• Individual MOS LQK decreases indicate bursty
impairment.
Cross-check with Conceal Ratio and Conceal Seconds
for evidence of packet loss and jitter.
• Check to see if the conference phone is using a
different codec than expected (RxType and
TxType).
• Check to see if the MOS LQK version changed
after a firmware upgrade.
Network impairment from packet loss or high jitter.
• Noise or distortion in the audio channel such as
echo or audio levels.
• Tandem calls that undergo multiple
encode/decode such as calls to a cellular
network or calling card network.
Check packet transmit (TxCnt) and packet receive
(RxCnt) counters to verify that voice packets are
flowing.
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