C-2 Vipersat CDM-570/570L User Guide
Eb/No values as the input function and the modulator’s transmit power as the
output function. Only modulator transmit power is controlled by the algorithm
since the receive chain has its own automatic gain control. DPC can be applied
to any or all of the modems with the exception of the STDMA burst control
demodulators. Since the STDMA burst demodulators are SCPC fast acquisi-
tions receivers they cannot provide stable signal quality measurements (Eb/No).
This value is critical in closing the power loop control mechanism.
Note: STDMA is not susceptible to bursts at different power levels since it is a
standard SCPC demodulator — as long as the input C/N burst power
ranges comply with the performance specifications of the modem. An
example is an operation using meshed video carriers.
DPC is a modulator function that cannot be enabled in remotes operating in
STDMA mode. DPC is automatically turned on when the remote switches to
SCPC mode.
Description
Operation of the DPC algorithm is controlled by the parameters shown in
table C-1, below.
Table C-1
Dynamic Power Control Parameters
Parameter Default Significance
Nominal Power
Level
-25 to -5
dBm
Power used for scaling Maximum power after
switching
Calibrated Data
Rate
System
Specific
Data Rate which is used for scaling Maximum
power after switching
Maximum
Power Level
System
Specific
Maximum transmit power level permitted based
on link/satellite parameters
Minimum
Power Level
System
Specific
Minimum transmit power level permitted based on
link/satellite parameters
Max Step Down
Power
3 dB Largest step reduction in transmit power permitted
Max Step Up
Power
3 dB Largest step increase in transmit power permitted
Target Eb/No 10 dB Target Eb/No value for which DPC is aiming
NOTE