Comtech EF Data CDM-425, Installation And Operation Manual

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CDM-425 Advanced Satellite Modem
Revision 0
Appendix F F–10 MN-CDM-425
F.2.3 Carrier-in-Carrier Latency
Carrier-in-Carrier has no measurable impact on circuit latency.
F.2.4 Carrier-in-Carrier and Adaptive Coding and Modulation
Carrier-in-Carrier is fully compatible with VersaFEC Adaptive Coding and Modulation (ACM)
mode of operation in the CDM-425 Advanced Satellite Modem.
Carrier-in-Carrier combined with VersaFEC ACM can provide 100-200% increase in average
throughput.
F.2.5 Carrier-in-Carrier Link Design
Carrier-in-Carrier 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 Carrier-in-Carrier until an optimal
combination is found.
For optimal Carrier-in-Carrier 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
following sections.
F.2.5.1 Symmetric Data Rate Link
Consider the example shown in Table F-3.
Table F-3. Symmetrical Data Rate Link Example
Satellite & Transponder Galaxy 18 @ 123º W, 13K/13K
Earth Station 1 Phoenix, AZ – 4.6 m
Earth Station 2 Phoenix, AZ – 2.4 m
Data Rate 512 kbps / 512 kbps