Comtech EF Data CDM-570A - Manual (Page 532)

CDM-570A/570AL Satellite Modem with Optional Packet Processor MN-CDM570A
Appendix G Revision 2
G–14
equivalent bandwidth when compared to the original side-by-side
8PSK, TPC 3/4 carriers:
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
VersaFEC
0.803
VersaFEC
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 BUC (W) 5 2 60%
Remote BUC (W) 20 5 75%
Using Carrier-in-Carrier and VersaFEC reduced the leased bandwidth by almost 44% and the BUC
size by 60% at the Hub and 75% at the Remote.
G.4.5.4 Commission and Deploy Carrier-in-Carrier
Prior to commissioning a Carrier-in-Carrier link, it is critical that the link is fully tested in non
Carrier-in-Carrier mode and all system issues including external interference, antenna pointing,
cabling, SSPA backoff are resolved. Only after the link is robust, should you attempt turning on
Carrier-in-Carrier. The following steps are recommended for Carrier-in-Carrier commissioning
and deployment:
Step Task
1 Turn ON the carrier at Site A. Carrier from Site B is OFF. CnC function is OFF at both sites.
 Using a spectrum analyzer, measure Co+No/No at the input to the modem at Site A.
 Using a spectrum analyzer, measure Co+No/No at the input to the modem at Site B.
 Measure/record Eb/No at Site B. Make sure there is sufficient margin to account for CnC.
 Measure/record Receive Signal Level (RSL) at Site B.
2 Turn OFF the carrier at Site A. Turn ON the carrier at Site B. CnC function is OFF at both sites.
 Using a spectrum analyzer, measure Co+No/No at the input to the modem at Site A.