Dmd1050Ts Automatic Uplink Power Control (Aupc) Operation; Radyne Aupc - Comtech EF Data DMD1050TS Installation And Operation Manual

3.13 DMD1050TS Automatic Uplink Power Control (AUPC) Operation

The modem has an optional, built-in provision for AUPC. AUPC is useful when operating power
levels are affected by environmental changes in the atmosphere. AUPC attempts to adjust local
power output to maintain a constant Eb/No at the receiver location.
The modem supports three versions of AUPC. They include Radyne AUPC, EF AUPC and Near
Side AUPC. Radyne AUPC and EF AUPC use satellite overhead to send messages between the
local and remote ends of an Single Carrier Per Channel (SCPC) link. The messaging is done with
IBS 1/15 and EF AUPC Framing messages.
Strap Code 26 use can set some of the modem configuration. See Appendix G for an explanation
and tabular listing of available Strap Codes. The Frequency and Modulator Output Power are set
independently of the strap code.
3.13.1

Radyne AUPC

In this case, Target Eb/No is the remote value the local unit wants to maintain by adjusting the
local power level.
The Radyne AUPC can be set to operate on either or both directions of a link, but always requires
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 applicable
framing for AUPC options to be editable and for the AUPC function to operate correctly.
Examples of the basic Radyne AUPC Operations:
•
Assume that the two modems, one at each end of the link, are set to Radyne AUPC
operation. Only one direction is discussed, but the same functions can occur in both
directions simultaneously.
•
The Local Modem is transmitting to the Remote modem under normal conditions, and the
Remote modem has a receive Eb/No of 7.5 dB. The Local modem has been set to a
Target Eb/No of 7.5 dB with an output power level of -15 dBm.
•
It starts to rain at the Remote site, and the Eb/No drops to –7.0 dB, then to –6.8 dB. The
Remote Modem is sending update messages of its Eb/No constantly to the Local
modem. When the Local modem sees the drop in the remote Eb/No, it starts to raise the
output power slowly, and continues to adjust, if the remote Eb/No continues to drop. As
the rain increases in intensity, the remote Eb/No decreases, but the Local modem
continues to increase its power level to compensate.
•
When the rain decreases, the Local modem sees the remote Eb/No start to increase. The
Local modem lowers its power level.
•
The operation is a feedback control loop, with the added complication of a significant time
delay.
Theory of Operation
DMD1050TS Satellite Modem Board
3–25
Revision 1
MN-DMD1050TS