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.
The Automatic Uplink Power Control (AUPC) 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.
3. Set the nominal output power of the modem: Use the SELECT: Config  Tx  Pwr
(Power) menu to select MANUAL mode, and then edit the displayed Tx output power
level.
4. Select AUPC as the operating mode. At this point, you are prompted to define four key
parameters: Target-Eb/No, Max-Range, Alarm, and DemodUnlock.
AUPC (Automatic Uplink Power Control)
CDM-570A/570AL Satellite Modem with Optional Packet Processor
E–1
Revision 5
MN-CDM570A