Comtech EF Data SLM-5650A Installation And Operation Manual page 481

G.3.4.3 Power Limited Links
Carrier-in-Carrier can provide substantial savings even when the original link is power limited.
Spreading the carrier by using a lower modulation and/or FEC along with latest FEC such as
VersaFEC can substantially reduce the total power which can then be traded with bandwidth
using Carrier-in-Carrier. The concept is illustrated with the following examples:
The conventional link is using 8-PSK, TPC 3/4:
Switching to VersaFEC and using a lower order modulation – e.g.,
QPSK, VersaFEC 0.803 increases the total occupied bandwidth,
while reducing the total power equivalent bandwidth:
Now using CnC, the second QPSK, VersaFEC 0.803 carrier can
be moved over the first carrier – thereby significantly reducing the
total occupied bandwidth and total power equivalent bandwidth
when compared to the original side-by-side 8PSK, TPC 3/4
carriers:
To continue, consider this example:
Satellite & Transponder
Earth Station 1
Earth Station 2
Data Rate
Appendix H
IS-901 @ 342º W, 22/22 (EH/EH)
Africa – 9.2 m
Africa – 4.5 m
2.048 Mbps / 2.048 Mbps
G–15
SLM-5650A Satellite Modem
Revision 10
MN-SLM-5650A