Mocomtech CDM-570 - Manual (Page 136)

CDM-570/570L Satellite Modem with Optional IP Module Revision 4
Front Panel Operation MN/CDM570L.IOM
6–12
VERY IMPORTANT NOTE:
The FEC type takes the highest configuration priority, and the selection here depends on
what, if any, optional plug-in codecs are installed. The choice of FEC type then
determines what modulation types, code rates, and data rates are available. The order of
hierarchy is therefore:
FEC type ► Modulation type ► Code Rate ► Data Rate
(Highest)
(Lowest)
If the user changes a parameter within this hierarchy, the other parameters may become
invalid. In this case, the software will change those other parameters, in order that the
configuration remains valid at all times.
Example: Suppose the user has selected Viterbi + Reed-Solomon, QPSK, Rate 1/2.
Now, the user changes the modulation type from QPSK to 16-QAM. In this case, Rate
1/2 is no longer a valid code rate, and so it will be automatically changed to the nearest
valid code rate (Rate 3/4).
Each of the configuration sub-branches will now be described in detail.
6.7.1 (CONFIG, TX) FEC TYPE
IMPORTANT NOTE: All possible choices are presented at all times. If an option is
not installed (either Hardware, or FAST) or valid, the
◄ ► arrow keys will force the
cursor to skip past the unavailable choice.
CASE RULES COMMENT
Viterbi ALWAYS VALID
Vit+RS (Viterbi +Concatenated
Reed-Solomon) If the RS codec is installed
TCM+RS (Trellis Coded
Modulation + Concatenated
Reed-Solomon)
If the RS codec is installed
AND 8-PSK FAST is enabled Fixed at 8-PSK
and Rate 2/3
TPC (Turbo Product Codec) If the TPC codec is installed
LDPC (Low Density Parity
Check Codec) WHEN
AVAILABLE (consult
factory)
If the TPC/LDPC codec is
installed
Uncoded Always valid - BPSK, QPSK
and OQPSK only. Forces Code Rate
to 1:1 (uncoded)
Tx FEC: Viterbi Vit+RS
TCM+RS TPC LDPC Uncoded
IMPORTANT
IMPORTANT