Cisco 6800 Series Maintenance Manual page 4

Voice Quality Troubleshooting Tips
You can access voice quality metrics from the Cisco IP Phone using the Call Statistics screen or remotely by
using Streaming Statistics.
Voice Quality Troubleshooting Tips
When you observe significant and persistent changes to metrics, use the following table for general
troubleshooting information.
Table 2: Changes to Voice Quality Metrics
Metric Change
Conceal Ratio and Conceal Seconds increase
significantly
Conceal Ratio is near or at zero, but the voice quality
is poor.
MOS LQK scores decrease significantly
MOS LQK scores increase significantly
Note
Voice quality metrics do not account for noise or distortion, only frame loss.
Maintenance
4
Condition
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.
Network impairment from packet loss or high jitter
levels:
• Average MOS LQK decreases may indicate
widespread and uniform impairment.
• Individual MOS LQK decreases may indicate
bursty impairment.
Cross-check the 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.
Maintenance