Cisco 8821

Procedure
Step 1
Access the Settings app.
Step 2
Select Admin settings > Reset settings > Security settings.
Step 3
Press Reset.
Voice Quality Monitoring
To measure the voice quality of calls that are sent and received within the network, Cisco IP Phones use the
following 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
Shows the ratio of concealment frames over total speech frames. An interval conceal ratio is calculated
every 3 seconds.
Concealed Second metrics
Shows the number of seconds in which the DSP plays concealment frames due to lost frames. A severely
“concealed second” is a second in which the DSP plays more than 5 percent concealment frames.
MOS-LQK metrics
Uses a numeric score to estimate the relative voice listening quality. The phone calculates the mean
opinion score (MOS) for listening quality (LQK) based audible concealment events due to frame loss
in the preceding 8 seconds, and includes perceptual weighting factors such as codec type and frame
size.
MOS LQK scores are produced by a Cisco proprietary algorithm, Cisco Voice Transmission Quality
(CVTQ) index. Depending on the MOS LQK version number, these scores might be compliant 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.
Concealment ratio and concealment seconds are primary measurements based on frame loss while MOS
LQK scores project a “human-weighted” version of the same information on a scale from 5 (excellent) to
1 (bad) for measuring listening quality.
Note
Listening quality scores (MOS LQK) relate to the clarity or sound of the received voice signal. Conversational
quality scores (MOS CQ such as G.107) include impairment factors, such as delay, that degrade the natural
flow of conversation.
For information about configuring voice quality metrics for phones, see the phone metrics sections in the
Cisco Unified Communications Manager documents.
You can access voice quality metrics on the phone or remotely by using Streaming Statistics.
Cisco Wireless IP Phone 8821 and 8821-EX Administration Guide for Cisco Unified Communications Manager
107
Maintenance
Voice Quality Monitoring