Other Considerations; Dpd And Doubletalk Carrier-In-Carrier; Dpd And Adaptive Coding And Modulation (Acm; Dpd And Automatic Uplink Power Control (Aupc - Comtech EF Data CDM-760 Installation And Operation Manual

Appendix L
CDM-760 Advanced High-Speed Trunking Modem
L.6

Other Considerations

L.6.1 DPD and DoubleTalk
DPD cannot be used with DoubleTalk Carrier-in-Carrier since this would involve transmitting two
carriers simultaneously over the same transponder. DPD can only compensate for the nonlinear
transponder in a single-carrier-per-transponder application.
L.6.2

DPD and Adaptive Coding and Modulation (ACM)

Local DPD can operate in constant coding and modulation (CCM) mode only, because the
modem uses the Rx port to receive predistortion feedback. Because of this, since the distant-
end modem cannot signal Es/No readings back to the transmit modem, the ACM system does
not have the information it needs to select the best modulation and coding combination.
Remote DPD is fully compatible with both ACM and CCM.
L.6.3

DPD and Automatic Uplink Power Control (AUPC)

DPD is fully compatible with AUPC.
L.6.4

DPD Latency

DPD has no measureable effect on signal latency.
®
Carrier-in-Carrier
L–12
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Revision 4
MN-CDM760