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Cisco Unified IP Conference Station 7937G Administration Guide for Cisco Unified Communications Manager 6.0
OL-11560-01 Rev. B0
Chapter 9 Troubleshooting and Maintenance
Resolving Conference Call Reception Problems
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 conference station uses. The following codecs
provide these maximum MOS LQK scores under normal conditions with zero frame loss:
•
G.711 codec gives 4.5 score
•
G.719A/ AB gives 3.7 score
A Conceal Ratio of zero indicates that the IP network is delivering frames and packets on time with no
loss.
When you observe significant and persistent changes to metrics, use
Table 9-3
for general
troubleshooting information.
Note
Voice quality metrics do not account for noise or distortion, only frame loss.
Resolving Conference Call Reception Problems
To ensure optimum performance with the conference station and the external microphones, see
“Guidelines for Best Performance” section on page 3-9
and the
“Conference Room Setup Examples”
section on page 3-10
.
Table 9-3
Changes to Voice Quality Metrics
Metric Change
Condition
MOS LQK scores decrease
significantly
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.
MOS LQK scores decrease
significantly
•
Check to see if the conference station is using a different
codec than expected (RxType and TxType).
•
Check to see if the MOS LQK version changed after a
firmware upgrade.
Conceal Ratio and Conceal
Seconds increase significantly
•
Network impairment from packet loss or high jitter.
Conceal Ratio is near or at zero,
but the voice quality is poor
•
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.
Check packet transmit (TxCnt) and packet receive (RxCnt)
counters to verify that voice packets are flowing.
