Paradyne DMD15L operation manual Aupc Functions, Function Description

DMD15/DMD15L IBS/IDR Satellite Modem Operation

The IBS Async Framer Data Mode provides a service channel between the two sites of a link permitting the modem processors to send messages and get responses over this channel. AUPC can be set to operate on either or both directions of a link but always requires a bi-directional channel. Therefore, both the Modulator and Demodulator interface mode must be set to IBS Async for the AUPC menus to be visible and for the AUPC function to operate properly. The AUPC Functions and their descriptions are shown on Table 3-2.

	Table 3-2. AUPC Functions
Function		Description
AUPC ENABLE/DISABLE		Enables/Disables the AUPC to function locally
AUPC Eb/No		Desired Eb/N0 of remote modem
AUPC MIN LVL		Sets minimum output power to be used
AUPC MAX LVL		Sets maximum output power to be used
AUPC DEF LVL		Sets default output power to be used

Note: The AUPC menus are located under the Modulator Menu as shown in Section 4.

The basic AUPC Operation is 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. Modem “A” is transmitting to modem “B” under normal conditions and modem “B” has a receive Eb/No of 7.5 dB. Modem “A” has been set to an AUPC Eb/No on the Front Panel of

7.5dB, and is currently outputting –15 dBm. Next, it begins raining at location “B”, and the Eb/No drops to –7.0 then –6.8 dB. Modem “B” is constantly sending update messages to “A” and reports

the current Eb/No. When “A” sees the drop in Eb/No, it slowly begins to raise the output power, and raises it again when it sees further drops. As the rain increases in intensity, and the Eb/No decreases again, “A” continues to increase its power level to compensate, and when the rain diminishes and quits, it lowers its power level to compensate. The operation is therefore a feedback control loop with the added complication of a significant time delay.

There are safeguards built into the AUPC System. First, the Modulator has two additional parameters, which allow control of the Maximum and Minimum Power Output Levels. Second, a default power level is specified which takes precedence over the output power level during signal loss or loss of AUPC Channel Communication. The default power level should normally be set to a high enough level to reestablish communication regardless of rain fade. The other controls are built into the operating control software to limit response times and detect adverse operating conditions.

TM051 - Rev. 5.8 3-23