Appendix P. Adaptive Coding And Modulation (Acm) Option; Overview - Comtech EF Data CDM-570A Installation And Operation Manual

Appendix P. ADAPTIVE CODING
MODULATION (ACM) OPTION
AND
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
Group.
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
Adaptive Coding and Modulation (ACM) Option
CDM-570A/570AL Satellite Modem with Optional Packet Processor
P–1
Revision 5
MN-CDM570A