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.