Comtech EF Data CDM-570AL - Appendix G. Doubletalk Carrier-In-Carrier Option; Overview; What Is Doubletalk Carrier-In-Carrier

CDM-570A/570AL Satellite Modem with Optional Packet Processor
Revision 5
DoubleTalk Carrier-in-Carrier Option G–1 MN-CDM570A
Appendix G. DOUBLETALK
CARRIER-IN-CARRIER OPTION
G.1 Overview
Space segment costs are typically the most significant operating expense for any satellite-based
service, having a direct impact on the viability and profitability of the service. For a satellite
transponder that has finite resources in terms of bandwidth and power, the leasing costs are
determined by bandwidth and power used. Therefore, a satellite circuit should be designed for
optimal utilization to use a similar share of transponder bandwidth and power.
The traditional approach to balancing a satellite circuit – once the satellite and earth station
parameters are fixed – involves trade-off between modulation and coding. A lower order
modulation requires less transponder power while using more bandwidth; conversely, higher
order modulation reduces required bandwidth, albeit at a significant increase in power.
Comtech EF Data has added a new dimension to satellite communication optimization:
DoubleTalk Carrier-in-Carrier.
G.2 What is DoubleTalk Carrier-in-Carrier?
The DoubleTalk Carrier-in-Carrier (CnC) option uses a patented signal processing algorithm
developed by Raytheon Applied Signal Technology that allows both the forward and reverse
carriers of a full duplex link to share the same segment of transponder bandwidth, using patented
“Adaptive Cancellation.” Raytheon Applied Signal Technology uses the term DoubleTalk, and
Comtech EF Data refers to it as DoubleTalk
Carrier-in-Carrier (CnC)
1
.
1
DoubleTalk
®
is licensed from Raytheon Applied Signal Technology.
DoubleTalk
®
is a registered trademark of Raytheon Applied Signal Technology.
WARNING! BEFORE ATTEMPTING TO COMMISSION A SATELLITE LINK USING
CARRIER-IN-CARRIER, YOU MUST ENSURE THAT THE LINK IS ROBUST ENOUGH FOR
NORMAL OPERATION. ONLY WHEN THIS HAS BEEN DONE – AND ALL SYSTEM ISSUES
(E.G., ANTENNA-POINTING, CABLING, TERRESTRIAL INTERFERENCE, SATELLITE
INTERFERENCE, ETC.) HAVE BEEN RESOLVED – SHOULD YOU ATTEMPT THE USE OF
CARRIER-IN-CARRIER.
DoubleTalk Carrier-in-Carrier (CnC) and Carrier-in-Carrier Automatic Power Control (CnC-
APC) are UNAVAILABLE and DISABLED when the CDM-570A/AL is configured to run in
CDM-570 Compatible Mode.