Comtech EF Data CDM-625A, Installation And Operation Manual

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CDM-625A Advanced Satellite Modem MN-CDM625A
Front Panel Operation Revision 4
6–18
Otherwise, when Diff Encoder is selectable on the bottom line:
CONFIG: Tx

FEC

Diff Encoder On
Enc=None(Vit,Seq,TCM,TPC,LDPC,VFEC,ULL)
Diff Encoder=On (Off,On) (

)
Use the
▲▼
arrow keys to select the Diff Encoder as On or Off . Press ENTER :
When you select Differential Encoding=OFF, there is no way for the modem to
resolve the phase ambiguities associated with PSK modulations. For BPSK there is a
50% chance that the polarity of the data will be correct. In QPSK there is a 25%
chance that the data will be correct.
6.2.1.3.5 CONFIG: Tx

Mod (Modulation)
Mod=QPSK (B,Q,OQ,8PSK,16Q,8QAM)
FEC Rate=1/2 (1/2,3/4,7/8) (

)
Use the
◄ ►
arrow keys to select the Mod (modulation type) (top line) or the FEC Rate (bottom
line). Press ENTER . Then, use the ▲▼ arrow keys to change that parameter selection. The
Encoder type dictates the Modulation Type and FEC rate selections:
Encoder Type Modulation Type FEC Rate Choice
No Encoder
BPSK Fixed at 1/1
QPSK, OQPSK Fixed at 1/1
Non-Turbo Encoder
BPSK Fixed at 1/2
TCM 8-PSK ( FAST option) Fixed at 2/3
QPSK, OQPSK 1/2, 3/4, 7/8
16-QAM (Vit+RS only) 3/4, 7/8
TPC
(with TPC/LDPC hardware option
installed)
BPSK 5/16, 21/44
QPSK, OQPSK 1/2 (aka 21/44), 3/4, 7/8, 0.95
8-PSK ( FAST option) 3/4, 7/8, 0.95
16-QAM ( FAST option) 3/4, 7/8
LDPC
(with TPC/LDPC hardware option
installed)
BPSK Fixed at 1/2
QPSK, OQPSK 1/2, 2/3, 3/4
8-PSK, 8-QAM ( FAST ) 2/3, 3/4
16-QAM ( FAST option) Fixed at 3/4
VFEC
BPSK Fixed at 0.488
QPSK 0.533, 0.631, 0.706, 0.803
8-QAM ( FAST option) 0.576, 0.642, 0.711, 0.780
16-QAM ( FAST option) 0.644, 0.731, 0.780, 0.829, 0.853
ULL
(VersaFEC Ultra-Low Latency)
BPSK Fixed at 0.493
QPSK 0.493, 0.654, 0.734