Cisco 7961G - IP Phone VoIP Administration Manual page 230

Monitoring the Voice Quality of Calls
Table 9-5
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.
Cisco Unified IP Phone 7961G/7961G-GE and 7941G/7941G-GE Administration Guide for Cisco Unified CallManager
9-24
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/de-
•
code such as calls to a cellular network or
calling card network.
Acoustic problems coming from a speaker-
•
phone, handsfree cellular phone or wireless
headset.
Check packet transmit (TxCnt) and packet receive
(RxCnt) counters to verify that voice packets are
flowing.
Chapter 9 Troubleshooting and Maintenance
OL-11528-01