Comtech EF Data CDM-625 - Page 350

CDM-625 Advanced Satellite Modem Revision 13
DoubleTalk
Carrier-in-Carrier Option MN-CDM625
10–14
To continue, consider this example:
Satellite & Transponder
IS-901 @ 342º W, 22/22 (EH/EH)
Earth Station 1
Africa – 9.2 m
Earth Station 2
Africa – 4.5 m
Data Rate
2.048 Mbps / 2.048 Mbps
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
Original Link
With Carrier-in-Carrier and VersaFEC
Savings
Hub to
Remote
Remote to
Hub
Total
Hub to
Remote
Remote to
Hub
Total
Data Rate (kbps)
2048
2048
2048
2048
Modulation
8-PSK
8-PSK
QPSK
QPSK
FEC
TPC 3/4
TPC 3/4
0.803
0.803
Occupied BW
(MHZ)
1.3
1.3
2.6
1.8
1.8
1.8
Power Eq. BW
(MHz)
2.2
1.0
3.2
1.1
0.5
1.6
Leased BW (MHz)
3.2
1.8
44%
Hub HPA (W)
5.0
2.0
60%
Remote HPA (W)
11.6
4.7
60%
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%.