CDM-570A/570AL Satellite Modem with Optional Packet Processor
Revision 5
Adaptive Coding and Modulation (ACM) Option P–1 MN-CDM570A
Appendix P. ADAPTIVE CODING
AND MODULATION (ACM) OPTION
P.1 Overview
VersaFEC and VersaFEC-2 are technologies that are wholly owned and
developed by Comtech EF Data and Comtech AHA Enterprise Products Group.
VersaFEC is a registered trademark of Comtech AHA Enterprise Products
The VersaFEC Adaptive Coding and Modulation (ACM) is a significant feature in the
CDM-570A/570AL. It may be used with either VersaFEC, or for modems running Firmware Version
1.5.2 or later, with a VersaFEC-2 plug-in Option Card.
The ACM serves as an operational enhancement for the CDM-570A/570AL-IP Satellite Modem (so
named when the CDM-570A, CDM-570AL, or CDMR-570AL modem is equipped with the optional
High-Performance Packet Processor):
• ACM turns fade margin into increased link capacity – gains of 100% or more are
possible, compared to traditional Constant Coding and Modulation (CCM). This is
accomplished by automatically adapting the modulation type and FEC code rate to give
highest possible throughput.
• ACM maximizes throughput regardless of link conditions (noise or other impairments,
clear sky, rain fade, etc). Initial setup is easy, and then requires no further user
intervention.
• With CCM systems, severe rain fading can cause the total loss of the link, and zero
throughput. ACM keeps the link up (with lower throughput) – and can yield much higher
system availability.
• ACM in the CDM-570A/570AL-IP is used in conjunction with VersaFEC and is currently
for IP traffic only.
The VersaFEC ACM feature requires activation of the appropriate FAST codes.
Chapter 5. FAST ACTIVATION PROCEDURE
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