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CDM-750 High Speed Trunking Modem
DoubleTalk Carrier-in-Carrier Option
8.4.5 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
IMPORTANT
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.
8.4.6 Symmetric Data Rate Link
Consider the following example:
Satellite & Transponder
Earth Station 1
Earth Station 2
Data Rate (Mbps)
The traditional link was based on 8PSK TPC 7/8 and required 36 MHz of leased bandwidth. The
1
LST
summary for the traditional link is as follows:
1
LST is Intelsat's Lease Transmission Plan Program.
Galaxy 18 @ 123º W, 13K/13K
Phoenix, AZ – 8.1 m
Phoenix, AZ – 8.1 m
34.368 (E3) / 34.368 (E3)
8–10
Revision 1
MN-CDM750
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