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CDM-625 Advanced Satellite Modem
DoubleTalk Carrier-in-Carrier Option
To continue, consider this example:
Satellite & Transponder
Earth Station 1
Earth Station 2
Data Rate
Whereas the original link used 8-PSK TPC 3/4, the Carrier-in-Carrier link used QPSK VersaFEC
0.803. The savings summary is as follows:
Item
Data Rate (kbps)
Modulation
FEC
Occupied BW
(MHZ)
Power Eq. BW
(MHz)
Leased BW (MHz)
Hub HPA (W)
Remote HPA (W)
Note: 1 dB HPA BO for QPSK, 2 dB HPA BO for 8-PSK, 1 dB Feed Loss.
Using Carrier-in-Carrier and VersaFEC reduced the leased bandwidth by almost 44% and HPA
power by 60%.
IS-901 @ 342º W, 22/22 (EH/EH)
Africa – 9.2 m
Africa – 4.5 m
2.048 Mbps / 2.048 Mbps
Original Link
Hub to
Remote to
Total
Remote
Hub
2048
2048
8-PSK
8-PSK
TPC 3/4
TPC 3/4
1.3
1.3
2.6
2.2
1.0
3.2
3.2
5.0
11.6
10–14
With Carrier-in-Carrier and VersaFEC
Hub to
Remote to
Remote
Hub
2048
2048
QPSK
QPSK
0.803
0.803
1.8
1.8
1.1
0.5
2.0
4.7
Revision 13
MN-CDM625
Savings
Total
1.8
1.6
1.8
44%
60%
60%
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