Chapter 12. Automatic Uplink Power Control; Introduction - Comtech EF Data CDM-600 Operating Instructions Manual

Chapter 12. AUTOMATIC UPLINK
12.1

Introduction

Automatic Uplink Power Control (AUPC) is a feature whereby a local modem is
permitted to adjust its own output power level in order to attempt to maintain the Eb/No
at the remote modem.
WARNING
To accomplish this, either the EDMAC or D&I++ framing types may be used. The
remote modem constantly sends back information about the demodulator Eb/No using
reserved bytes in the overhead structure. The local modem then compares this value of
Eb/No with a pre-defined target value. If the Remote Eb/No is below the target, the local
modem will increase its output power, creating a closed-loop feedback system over the
satellite link. A particularly attractive benefit of this feature is that whenever framed
operation is selected, the remote demodulator's Eb/No can be viewed from the front
panel display of the local modem. Note that both EDMAC and AUPC can be used
simultaneously with either framing type.
There are several important parameters associated with this mode of operation, and the
user needs to understand how the AUPC feature works, and the implications of setting
these parameters.
POWER CONTROL
The user 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
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