Comtech EF Data SLM-5650A Vipersat - Manual (Page 121)

Appendix C - Dynamic Power Control C-1
A
P P E N D I X
D
YNAMIC
P
OWER
C
ONTROL
Introduction
Dynamic Power Control (DPC) provides a mechanism whereby Vipersat satel-
lite links have their transmit power levels adjusted in order to optimize the
receive signal quality, as measured by the corresponding demodulator E
b
/N
0
.
This optimization process acts to either increase or decrease transmitted signal
levels in order to:
• Achieve a minimum level of received E
b
/N
0
consistent with providing an
error-free link.
• Reduce transmit power where sufficient link margin exists in order to
optimize station uplink and satellite transponder power usage, and reduce
costs.
• Increase link availability when margins apply (typically Ku-band).
DPC can be selectively enabled and disabled on a unit-by-unit basis and func-
tions as both a point-to-point and a point-to-multipoint control. DPC relies on
the passing of an IP message between the receive site, where the receive quality
is being measured, and the transmit site, where the power level is to be adjusted.
These DPC packets are IP unicast messages, directed to the transmit site as
forwarded from the corresponding dynamically assigned demodulator(s).
The Vipersat-optioned CEFD modem units have an algorithm that, when acti-
vated, automatically adjusts the modulator transmit power to maintain a
constant nominal receive signal quality (E
b
/N
0
) at the corresponding receive
site(s). This provides a mechanism to compensate for varying signal levels