Cisco 7971G-GE - IP Phone VoIP Fehlersuche und Wartung - Seite 22
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This section contains the following topics
Quality Report Tool
The Quality Report Tool (QRT) is a voice quality and general problem-reporting tool for the Cisco Unified IP
Phone. The QRT feature is installed as part of the Cisco Unified Communications Manager installation.
You can configure Cisco Unified IP Phones with QRT. When you do so, users can report problems with phone
calls pressing QRT. This softkey is available only when the Cisco Unified IP Phone is in the Connected,
Connected Conference, Connected Transfer, or OnHook states.
When a user presses QRT, 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 if the destination device is a Cisco Unified IP Phone.
For more information about using QRT, see the Cisco Unified Serviceability Administration Guide.
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 based on concealment events. The Digital Signal Processor (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 Cisco Unified
Note
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.
Troubleshooting and Maintenance
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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.
IP 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.
Troubleshooting and Maintenance