Chapter 5
Viewing Files
63
Analysis Display – The channel number and modulation type
are displayed the same as analog channels. Similarly, the location
and modulation type are displayed.
Digital – The digital channel’s Frequency and Average Power
Level measurement replaces the video carrier level measurement
and is shown in dBmV. All audio carrier and ratio (delta)
measurement results are dropped. Note that the frequency of the
digital channel is the center frequency for the channel, rather
than the video carrier frequency.
PreFEC BER - The PreFEC BER (Pre-FEC Bit Error Rate) is
the error rate of the incoming signal prior to being corrected by
the FEC (Forward Error Correction) circuitry in the Install
Profiler. A minimum of 1.0 E-7 should be expected, although
FEC may be able to correct errors as high as 1.0 E-6
PostFEC BER - The PostFEC BER (Post-FEC Bit Error Rate)
is the error rate of the signal after the FEC has resolved and
corrected all of the errors it can. Any errors not corrected by the
FEC will impair DOCSIS transmissions and decrease throughput.
1.0 E-9 is typical performance although any errors <1.0 E-0 will
reduce the data transfer rate.
MER - MER (Modulation Error Ratio), the digital equivalent of
signal-to-noise, is the measurement of the demodulated digital
signal in the noise (and other impairments) of its environment.
This measurement is based on constellation statistics and is the
ratio of where the data actually plots on a constellation to the
ideal center of the constellation decision window. A minimum
of 22 dB MER is needed for 64 QAM, 28 dB for 256 QAM.
Adjacent Channel – Displays the channel number and
modulation type of the adjacent channel.
Adjacent Video – Displays the frequency of the adjacent carrier
and level measurement of the upper adjacent video carrier in
dBmV.
Adjacent Channel Ratio – This display will be added in future
releases of the PC-IP firmware. Displays the result of the
difference in level between the primary channel’s level
measurement and the measurement of the upper adjacent channel
in dB. This measurement and calculation is only made if the
upper adjacent video carrier is within the nominal channel
bandwidth of the tuned channel.
