VoIPCheck CMTS Loop test (optional purchase required) displays VoIP call statistics without MTA provisioning. The VoIPCheck CMTS Loop test is a continuous test. During a VoIPCheck CMTS Loop test, packetloss, jitter, delay, R-Value and MOS values are displayed in a table format. To perform the VoIPCheck CMTS Loop test, press the VIEW softkey, use the arrow keys to select VoIPCheck, press ENTER.

NOTE:

- VoIP test can only be initiated after the meter has successfully registered with the CMTS, and the MTAs has successfully initialized.
- VoIP mode cannot be initiated if Ranging Only is configured.
- The test will not run if registration with the CMTS has failed.

Measurement Data

The VoIPCheck CMTS Loop display contains Packet and Quality measurement data. The VoIPCheck CMTS Loop data is captured and continuously updated during the VoIPCheck test process.

Packet loss, delay and jitter are factors that affect voice quality on a VoIP network. Details of each parameter is provided as follows:

Packet loss

Significant packet loss degrades voice quality. Packet loss occurs when packets are lost on a network, when packets are delayed too long, when packets arrive out of order. Packet loss can cause reconstructed speech to sound choppy and distorted.

Delay

Total end-to-end packet delays severely degrade voice quality by causing long delays between callers and causing echo problems. Any packet delays less than 150 ms provide acceptable speech quality. Delays greater than 150 ms begin to interfere with conversations and cause noticeable degradation.

Jitter

Jitter
occurs when packets are sent at equal intervals, but received at uneven time intervals, this can cause audible pops, clicks and a greater delay of audio communications. Gateways compensate for this by accumulating the received packets into an internal buffer and "playing them out" at the proper time intervals and in packet order. The more jitter buffer available, the more the network can reduce the effects of jitter.

R-Value and MOS are computed using the packet loss, jitter and delay information. These values are intended to give a quantitative assessment of a call. Details of each parameter is provided as follows:

MOS

The Mean Opinion Score (MOS) Listening value is a conversion of the Listening R-Value based on the ITU G.107 conversion formula. The Mean Opinion Score (MOS) for listening represents a quantitative value base solely on the local packet loss, jitter and delay measurements. The value range for MOS is 0.0 to 5.0.

R-Value

The R-Value number represents a quantitative measurement value based solely on the packet loss, jitter and delay measurements. The value range for R-Value is 0 to 93.

Softkeys

VIEW

The Limits menu allows you to directly display the Range, Register, Throughput, Ping, Packet Loss, CMTS Loop, and Segmentation screens. To select a different screen, press the VIEW softkey, use the arrow keys to select desired mode, press ENTER.

LIMITS

Press the LIMITS softkey and use the arrow keys to select the limit set you prefer - Tap, Ground Block, TV, Cable Modem, or Off. Press ENTER to make your selection.

RESET

Select Reset to manually reset the displayed measurement data.