Comtech EF Data CDM-625A Installation And Operation Manual page 643

Appendix M. ADAPTIVE CODING
MODULATION (ACM) OPTION
AND
M.1 Introduction
The VersaFEC® Adaptive Coding and Modulation (ACM) feature is a technology wholly owned and
developed by Comtech EF Data and CEFD sister division Comtech AHA Corp. It serves as an
operational enhancement for the CDM-625A Advanced Satellite Modem:
•
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 a CCM system, 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-625A is used in conjunction with VersaFEC and is currently for IP traffic
only.
M–1