Comtech EF Data CDM-570 - Manual (Page 187)

9–1
Chapter 9. AUTOMATIC UPLINK
POWER CONTROL (AUPC)
9.1 Introduction
You MUST obtain permission from the Satellite Operator to use this feature.
Improper use of this feature could result in a transmitting terminal seriously
exceeding its allocated flux density on the Operator’s satellite. This could
produce interference to other carriers, and could cause transponder saturation
problems.
Automatic Uplink Power Control (AUPC) is a feature whereby a local modem is permitted to adjust
its own output power level as a means to maintain the E
b
/N
0
at the remote modem.
To accomplish this, either the EDMAC or EDMAC-2 framed mode of operation must be used.
The remote modem constantly sends back information about the demodulator E
b
/N
0
using
reserved bytes in the overhead structure. The local modem then compares this value of E
b
/N
0
with
a pre-defined target value. If the Remote E
b
/N
0
is below the target, the local modem will increase
its output power, and hence, a closed-loop feedback system is created over the satellite link. A
particularly attractive benefit of this feature is that whenever framed operation is selected, the
remote demodulator’s E
b
/N
0
can be viewed from the front panel display of the local modem. Note
also that AUPC can be used simultaneously with EDMAC.
There are several important parameters associated with this mode of operation. You must
understand both how the AUPC feature works, and what the implications are for setting the
AUPC parameters.