Voice Quality Monitoring - Cisco 8831 Administration Manual

Voice quality monitoring

You can configure users' conference phones with QRT. When you do so, users can report problems with
conference phone calls by pressing the QRT softkey. This softkey is available only when the conference phone
is in the Connected, Connected Conference, Connected Transfer, or OnHook states.
When a user presses the QRT softkey, a list of problem categories appears. The user selects the appropriate
problem category and this feedback is logged in an XML file. Actual information logged depends on the user
selection and whether the destination device is a conference phone.
For more information about using QRT, see the Cisco Unified Communications Manager Features and
Services Guide.
Voice quality monitoring
To measure the voice quality of calls that are sent and received within the network, conference 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
• MOS-LQK metrics: Use a numeric score to estimate the relative voice listening quality. The conference
MOS LQK scores are produced by a Cisco proprietary algorithm that is an implementation of P.VTQ, an ITU
provisional standard.
Concealment ratio and concealment seconds are primary measurements based on frame loss while MOS
Note
LQK scores project a "human-weighted" version of the same information on a scale from 5 (excellent) to
1 (bad) for measuring listening quality.
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 conference phones, see the Cisco Unified
Communications Manager System Guide, "Cisco Unified IP Phones" chapter, "Phone Features" section.
You can access voice quality metrics from the conference phone by using the Call Statistics screen or remotely
by using Streaming Statistics.
To use 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.
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.
Cisco Unified IP Conference Phone 8831 Administration Guide for Cisco Unified Communications Manager
9.0
138
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.
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.
Troubleshooting and maintenance