Comtech EF Data CDM-760 - Manual (Page 387)

Appendix J Revision 2
CDM-760 Advanced High-Speed Trunking Modem MN-CDM760
J–9
J.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 appendix
sections that follow.
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.
J.4.6 Symmetric Data Rate Link
Consider this example:
Satellite & Transponder Galaxy 18 @ 123º W, 13K/13K
Earth Station 1 Phoenix, AZ – 8.1 m
Earth Station 2 Phoenix, AZ – 8.1 m
Data Rate (Mbps) 34.368 (E3) / 34.368 (E3)
The traditional link was based on 8PSK TPC 7/8 and required 36 MHz of leased bandwidth. This
is the LST 2 summary for the traditional link:
2 LST is Intelsat’s Lease Transmission Plan Program.