Cisco 7906G - Unified IP Phone VoIP Administration Manual page 243

Chapter 9 Troubleshooting and Maintenance
Table 9-4
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 Phone 7906G and 7911G for Cisco Unified Communications Manager 6.1
OL-14585-01
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.
Monitoring the Voice Quality of Calls
9-27