Chapter 9 Troubleshooting and Maintenance

Monitoring the Voice Quality of Calls

Table 9-4

Changes to Voice Quality Metrics

 

 

 

Metric Change

 

Condition

 

 

MOS LQK scores

Network impairment from packet loss or high jitter:

decrease significantly

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.

 

 

MOS LQK scores

Check to see if the phone is using a different

decrease significantly

codec than expected (RxType and TxType).

 

 

Check to see if the MOS LQK version changed

 

 

after a firmware upgrade.

 

 

Conceal Ratio and

Network impairment from packet loss or high

Conceal Seconds

jitter.

increase significantly

 

 

 

Conceal Ratio is near or

Noise or distortion in the audio channel such as

at zero, but the voice

echo or audio levels.

quality is poor

 

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.

 

 

 

Note Voice quality metrics do not account for noise or distortion, only frame loss.

Cisco Unified IP Phone Administration Guide for Cisco Unified CallManager 5.1 (SIP), Cisco Unified IP Phones

 

OL-11524-01

9-23

 

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