P.1 overview, Appendix p. adaptive, Coding – Comtech EF Data CDM-570A User Manual
Page 591: Modulation, Acm), Option
P–1
Appendix P. ADAPTIVE
CODING
AND
MODULATION
(ACM)
OPTION
P.1 Overview
The VersaFEC® Adaptive Coding and Modulation (ACM) feature is a patents-pending technology,
wholly owned and developed by Comtech EF Data and Comtech AHA Enterprise Products Group. It
serves as a significant 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 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-570A/570AL-IP is used in conjunction with VersaFEC and is for IP traffic
only.
The VersaFEC ACM feature requires activation of the appropriate FAST codes.
Chapter 5. FAST ACTIVATION PROCEDURE