Vislink Strata RX, Technical Reference Manual

Page: 44 / 186

Routine Operation 3-16
Strata RX
Operator’s Guide/Tech Ref Manual
3.4.7 Monitoring Bit Error Ratio (BER)
One useful indicator of digital signal quality is the Bit Error Ratio
(BER). The BER is calculated as:
The Strata RX reports two BER values:
• BER
before
Forward Error Correction (FEC), also called
“Pre-Viterbi BER”.
• BER
after
Forward Error Correction (FEC), also called
“Post-Viterbi BER”.
These would appear on the BER Monitor Screen as
Using BER
BER is one of the key components in Vislink’s
Link
Quality
indicator. It also can be used on its own to help alert the
operator to deteriorating signal quality.
As signal quality degrades, the Pre-Viterbi BER will increase.
However, the FEC algorithms will be able to correct these errors,
and the Post-Viterbi BER will be maintained at 0. Video and
audio will be undisturbed.
As the signal continues to degrade, the Pre-Viterbi BER will
increase as well. At some point the FEC algorithms will reach
the limit of errors they can correct. The uncorrected errors will
then appear in the Post-Viterbi BER. These Post-Viterbi errors
are a warning sign, even though the video may still be
acceptable.
If the Post-Viterbi BER becomes too large, the MPEG decoder
will be unable to make sense of the data, and video will be lost.
Error Bits Detected / Total bits received
PRE 2.0E-7
POST 0.0E-7
Monitoring the BER screen will help you be aware of this signal
degradation so you can take corrective action.
To access the BER Monitor Screen, follow these steps:
Be sure Strata is connected and powered.
See “Setting Up” and “Turning the power
ON and OFF”.
Start at the Main Screen.
Turn the Control Switch RIGHT until the
display shows the BER Monitor Screen. It
will be similar to this:
Note
- The BER will update more slowly
with low BER readings, faster with high
BER readings.
To lock this screen on the display, also do the following:
Push the Control Switch to lock the display
on this screen. Data on display will
continue to update.
To allow the screen to default normally to the Main
Screen, do the following:
Push the Control Switch to unlock the
display.
Display changes back to Main Screen.
Preset #3
-43.2 dBm LQ7
PRE 2.0E-7
POST 0.0E-7