Release 1.0
Configuring the CMTS
526360-001-00 Rev. B
MGBI
6-43
Recommended Post Equalization Upstream Modulation
Profiles
This section lists and describes the recommended Post Equalization modulation
profiles to use with the BSR 2000. The recommended standard Post Equalization
modulation profile as well as several customizations are included. Refer to
for information on using the CLI to create and apply modulation
profiles.
Standard Opening POST EQ
The recommended modulation profile for Standard Opening POST EQ is as follows:
cable modulation-profile 9 request 0 16 2 qpsk scrambler 0x152 no-diff 68 fixed
cable modulation-profile 9 initial 5 34 0 qpsk scrambler 0x152 no-diff 320 fixed
cable modulation-profile 9 station 5 34 0 qpsk scrambler 0x152 no-diff 320 fixed
cable modulation-profile 9 short 2 75 7 16qam scrambler 0x152 no-diff 384 short
cable modulation-profile 9 long 5 220 0 16qam scrambler 0x152 no-diff 384 short
However, operators may customize the modulation profile in order to:
■
accommodate the existing plant characteristic, such as SNR (Signal to Noise
Ratio) and
■
reduce physical overhead which does result into higher throughput.
FEC encoding is designed to correct errors due to burst noise. The number of FEC
Error Correction (T) determines the number of bytes that can be detected and
corrected per FEC codeword. At the same time, it would costs 2*T bytes of over head.
So, reducing the number of FEC correction bytes (which are 2 and 5 bytes for short
and long data IUC in the modulation profile 9 shown above) increases the throughput.
In the same way, the longer preamble length costs more over head byte per upstream
burst, but it does help the POST-Equalizer to correct micro-reflection in the line. At
the bottom line, in order to meet the optimum point, the plant characteristic has to be
determined by an RF engineer. Below are examples of recommended modulation
profiles with the corresponding assumed plant characteristic.
POST EQ Profile Option - Given 26 dB < SNR < 30 dB for MOD 9
The presumption here is that the carrier Frequency is high and multiple AMP
Cascades are present.
cable modulation-profile 11 request 0 16 2 qpsk scrambler 0x152 no-diff 68 fixed
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