Using Voice Quality Metrics; Troubleshooting Tips - Cisco 7921G - Unified Wireless IP Phone VoIP Administration Manual

Chapter 10 Troubleshooting the Cisco Unified Wireless IP Phone 7921G
You can access voice quality metrics remotely by using Streaming Statistics (see
the Cisco Unified Wireless IP Phone Remotely."

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:
•
•
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.
Table 10-1
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
Cisco Unified Wireless IP Phone 7921G Administration Guide for Cisco Unified Communications Manager Release 7.0
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G.711 codec gives 4.5 score
G.729A/ AB gives 3.7 score
Changes to Voice Quality Metrics
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 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.
• Acoustic problems coming from a speakerphone, handsfree
cellular phone or wireless headset.
Check packet transmit (TxCnt) and packet receive (RxCnt) counters
to verify that voice packets are flowing.
Resolving Voice Quality and Roaming Problems
Chapter 9, "Monitoring
Table 10-1 for general
10-13