Comtech EF Data CDM-Qx, Инструкция по установке и эксплуатации

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Appendix D. Carrier-in-Carrier
®
PERFORMANCE
CHARACTERIZATION
D.1 Carrier-in-Carrier
®
Description
DoubleTalk™ Carrier-in-Carrier
®
(CnC) is an adaptive cancellation technology that
significantly reduces bandwidth occupancy by allowing two carriers to simultaneously
occupy the same spectral location, a practice that is disastrous for normal carriers. By
comparison, standard carriers must occupy non-overlapping spectral segments with no
more than one carrier in the same space.
In a number of ways, CnC carriers behave similar to conventional carriers in satellite
links. They are both exposed to adjacent carriers, cross-polarization and rain fade, and
exhibit impairments when any of these become too great. In addition, CnC operates in an
environment where:
•
Carriers intentionally occupy the same spectral slot
•
Performance depends upon desired and co-located interfering carrier.
Several areas relating to CnC performance are discussed, including:
•
Adjacent carrier performance
•
Eb/No Degradation as a function of the CnC ratio
•
Symbol rate ratio
•
Carrier offset
•
The effects of rain fade and asymmetric antennas.
Nominally, these effects are treated independently so it is possible to add them together
to estimate the total degradation. Initially, degradation due to carrier spacing is examined
to characterize the adjacent carrier performance. Next, the CnC ratio is evaluated to
D–1