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C.2
Processing Flow and Symbol Rate Calculation
The modem supports Ethernet interface and provides options for framing, modulation and
spreading. Figure C-1 shows the processing flow for these functions.
Figure C-1. SLM-5650C/ SLM-5650C-ODU – Feature Block Diagram
The symbol rate
FEC encoding, modulation, and transport overhead factors as shown in the equation
"S
=B
/M
C
F
R
R
O
R
Operands:
•
Operand 1 –
•
Operand 2 –
•
Operand 3 –
o
o
Only one of these two features (AUPC Mode or ACPC Mode) may be enabled
at any given time.
•
Operand 4 –
o
o
If the DSSS feature is enabled, then the simple equation for Chip Rate (SC)
equivalent to (Bw) of the spread signal is: "SC=K*SR" where 'K' is the
programmed spreading factor (e.g. 2, 4, 8, 16, 32, 64, up to 512)
Appendix C
S
(Carrier 3dB Bandwidth) is a function of the programmed data bit rate
R
(referred to hereafter as "Equation 1"), containing the following
F
F
"
RS
T
C
M
= Modulation Order
O
C
= Code Rate of the FEC (e.g., CR = 0.75 if stated FEC code rate = "3/4")
R
= AUPC Mode Framing Factor, where:
F
c
F
= 15/16 if AUPC Mode is enabled;
C
F
= 1 if neither feature is enabled.
C
F
= TRANSEC Framing Factor, where:
T
=
F
N*16/[N*16+3], where 'N' is the selected Frame Length in AES blocks per
T
frame, in the range of 1 to 16.
F
= 1 if the TRANSEC encryption is disabled.
T
SLM-5650C / SLM-5650C-ODU Satellite Modem
'1' if BPSK
'2' if QPSK
'3' if 8PSK
'4' if 16QAM
C–2
Revision 1
B
with
R
MN-SLM-5650C
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