Ef Aupc; Near Side Aupc; G.1.2 Ef Aupc - Comtech EF Data DMD-2050E Installation And Operation Manual

DMD2050E Universal Satellite Modem
drop in the remote Eb/No, it slowly begins to raise the output power, and will continue to adjust if
the remote Eb/No continues to drop. As the rain increases in intensity, the remote Eb/No
decreases but Local modem continues to increase its power level to compensate.
When the rain diminishes, Local modem will see the remote Eb/No begin to increase. Local
modem will lower its power level. The operation is therefore a feedback control loop with the
added complication of a significant time delay.

G.1.2 EF AUPC

In EF AUPC mode, the Target Eb/No indicates the local unit wants the remote unit to maintain a
power level sufficient to provide the local Eb/No value.
EF AUPC can be set to operate on either or both directions of a link but always require a bi-
directional channel. 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 to the appropriate
framing for AUPC options to be editable and for the AUPC function to operate properly.
Examples of the basic EF AUPC Operations are described as follows:
Assume that the two modems, one at each end of the link, are set to AUPC operation. Only one
direction is discussed, but the same functions could be occurring in both directions
simultaneously.
The local modem is transmitting to modem at a remote locale under normal conditions. The
remote modem has a receive Eb/No of 7.5 dB. The local modem has been set with a Target
Eb/No of 7.5 dB, and has a current power output of –15 dBm.
It begins to rain at the local site, and the Eb/No drops to –7.0 then –6.8 dB. The local modem is
constantly sending update messages of its Eb/No to the remote modem. When the remote
modem sees the drop in the Eb/No, it slowly begins to raise its output power, and will continue to
do so until the Target Eb/No is restored at the local site.
When the rain diminishes, the local modem's Eb/No will begin to increase. The remote modem
will now lower its power level to restore the target value. The operation is therefore a feedback
control loop with the added complication of a significant time delay.
G.1.3 Near Side AUPC
Near Side AUPC is a loop back system that adjusts the broadcast uplink signal when local
conditions change. This is done by having the Near Side AUPC attempt to adjust the outbound
power to compensate for local weather.
MN-DMD2050E Revision 2
AUPC Operation
G–2