Comtech EF Data SLM-5650A Vipersat - Manual (Page 122)

Introduction
C-2 Vipersat SLM-5650A User Guide
caused, for example, by the use of different antenna sizes in a mesh network, or
by rain fade conditions. Receive signal quality and use of system resources is
optimized, resulting in a reduction in power amplifier intermodulation as well as
conservation of satellite transmit power.
The power control algorithm is a closed loop servo-mechanism with the
received E
b
/N
0
values as the input function and the modulator transmit power as
the output function. Only modulator transmit power is controlled by the algo-
rithm since the transmit up-conversion chain is typically a fixed gain block.
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 acquisition receivers, they cannot provide stable signal quality
measurements (E
b
/N
0
). This value is critical in closing the power loop control
mechanism.
Note: The power control function for a DPC-enabled unit is active only when
that unit is operating in SCPC mode, and is inactive when operating in
STDMA mode.
NOTE