Appendix E. Aupc (Automatic Uplink Power Control; Overview; Setting Aupc Parameters - Comtech EF Data CDM-570A Installation And Operation Manual

Appendix E. AUPC (AUTOMATIC
UPLINK POWER CONTROL)
E.1

Overview

WARNING! 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.
AUPC is the acronym for Automatic Uplink Power Control. This feature permits a local
CDM-570A/570AL to adjust its own output power level in order to attempt to maintain the
Eb/No at the remote CDM-570A/570AL. To accomplish this, you must use the EDMAC or
EDMAC-2 framing type.
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. You must
understand how the AUPC feature works, and what the implications are for setting these
parameters.
E.2

Setting AUPC Parameters

You must enable EDMAC framing. Do these steps:
1. Use the SELECT: Config  Frame  EDMAC or EDMAC-2 menu to select EDMAC+AUPC
framing. You may then define the unit as an EDMAC Master or Slave.
2. Verify that the remote modem also has EDMAC framing enabled.
E–1