Voice Quality Monitoring; Voice Quality Metrics - Cisco 3905 Administration Manual

Troubleshooting and Maintenance
Procedure
Step 1 Unplug the power cable from the phone and then plug it back in.
The phone begins its power-up cycle.
Step 2
While the phone is powering up, press and hold # until the Line LED turns green.
Step 3 Release the # button and press 123456789*0#.
The phone reboots when it is finished.

Voice Quality Monitoring

To measure the voice quality of calls that are sent and received within the network, Cisco Unified IP Phones
use these statistical metrics that are based on concealment events. The DSP plays concealment frames to mask
frame loss in the voice packet stream.
• Concealment Ratio metrics: Show the ratio of concealment frames over total speech frames. An interval
• Concealed Second metrics: Show the number of seconds in which the DSP plays concealment frames
• Mean Opinion Score (MOS) for Listening Quality (LQK) Voice Metrics: Uses a numeric score to
Concealment ratio and concealment seconds are primary measurements based on frame loss. A Conceal
Note
Ratio of zero indicates that the IP network is delivering frames and packets on time with no loss.
You can access voice quality metrics remotely by using Streaming Statistics (see the
page 63

Voice Quality Metrics

When using the metrics for monitoring voice quality, note the typical scores under normal conditions of zero
packet loss and use the metrics as a baseline for comparison.
conceal ratio is calculated every 3 seconds.
due to lost frames. A severely concealed second is a second in which the DSP plays more than five
percent concealment frames.
estimate the relative voice-listening quality. The Cisco Unified IP Phones calculate the MOS LQK based
audible-concealment events due to a frame loss in the preceding 8 seconds and includes weighting factors
such as codec type and frame size.
MOS LQK scores are produced by a Cisco-proprietary algorithm, the Cisco Voice Transmission Quality
(CVTQ) index. Depending on the MOS LQK version number, these scores may comply with the
International Telecommunications Union (ITU) standard P.564. (This standard defines evaluation methods
and performance accuracy targets that predict listening quality scores based on observation of actual
network impairment.)
chapter).
Cisco Unified SIP Phone 3905 Administration Guide for Cisco Unified Communications Manager 8.6 (SIP)
Voice Quality Monitoring
Remote Monitoring, on
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