Comtech EF Data CDM-750 - Manual (Page 268)

CDM-750 Advanced High-Speed Trunking Modem Revision 2
Appendix D MN-CDM750
D–10
D.4.4 Carrier-in-Carrier and Adaptive Coding and Modulation (ACM)
Appendix C. ADAPTIVE CODING AND MODULATION (ACM) OPTION
DoubleTalk Carrier‐in‐Carrier is fully compatible with the Adaptive Coding and Modulation
(ACM) mode of operation in the CDM‐750.
CnC combined with ACM can provide 100 – 200% increase in average throughput.
D.4.5 Carrier-in-Carrier Link Design
CnC link design involves finding the FEC and modulation combination that provides optimal
bandwidth utilization. Just like conventional link design, it is an iterative process that involves
trying different FEC and modulation combinations with CnC until an optimal combination is
found.
For optimal CnC performance, it is recommended that the two carriers have similar symbol rate
and power. This can be achieved by selecting appropriate ModCods, as shown in the sections
that follow in this chapter.
Normally, a CnC link results in saving bandwidth and power, so there are satellite
resources recovered that are deployable for additional links and more
throughput over the existing capacity. When sizing the link to transform existing
carriers into CnC links, also consider how the recovered capacity is best deployed.
In other words, evaluate the bandwidth and power (or power equivalent
bandwidth) tradeoffs with an eye to the future.