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DMD2050E Universal Satellite Modem
The local receiver must be tuned and locked to the transmitter and then the internal Eb/No., is
used for feedback. This creates a Tx-Satellite-Rx control loop.
Near Side AUPC is primarily used for broadcast applications since the modem cannot expect to
receive data from a distant location. Near Side AUPC can be utilized with any satellite framing or
Network mode.
There are safeguards built into the AUPC System. First, the modulator has two parameters,
which allow control of the maximum and minimum output power Levels. Second, a nominal, or
default, power level is specified which takes effect if the receive signal or messaging is lost. This
nominal power should be set to a level high enough to re-establish communications regardless of
rain fade.
EF AUPC also provides some control over the rate of power change; while the Radyne and Near
Side AUPC use a optimized rate for rain fade compensation.
G.1.4 EBEM AUPC
In this case, Target Es/No indicates the remote value the local unit wants to maintain by adjusting
the local power level.
EBEM AUPC can be set to operate on either or both directions of a link but always require a bi-
directional channel operating in EBEM Mode. Enabling AUPC on one side of the link will activate
AUPC on the distant end of the link. It is necessary that both the Modulator and Demodulator be
set with the embedded channel enabled and ITA mode disabled for EBEM AUPC options to be
editable and for the AUPC function to operate properly.
Examples of the basic EBEM AUPC Operations are described as follows:
Assume that the two modems, one at each end of the link, are set to EBEM AUPC operation.
Only one direction is discussed, but the same functions could be occurring in both directions
simultaneously.
Local Modem is transmitting to Remote modem under normal conditions and the Remote modem
has a receive Es/No of 7.5 dB. Local modem has been set to a Target Es/No of 7.5 dB with an
output power level of -15 dBm.
It begins raining at Remote site and the Es/No drops to –7.0 then –6.8 dB. Remote Modem is
constantly sending update messages of its Es/No to Local modem through the embedded
channel. When Local modem sees the drop in the remote Es/No, it slowly begins to raise the
output power, and will continue to adjust if the remote Es/No continues to drop. As the rain
increases in intensity, the remote Es/No decreases but Local modem continues to increase its
power level to compensate.
MN-DMD2050E Revision 2
AUPC Operation
G–3
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Troubleshooting
