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D–1
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.