Mocomtech CDM-QX - Manual (Page 183)

8–1
Chapter 8. AUTOMATIC UPLINK
POWER CONTROL (AUPC)
8.1 Introduction
The user 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.
Automatic Uplink Power Control (AUPC) is a feature whereby a local modem is permitted to adjust
its own output power level in order to attempt to maintain the E
b
/N
o
at the remote modem.
To accomplish this, the EDMAC framing type of operation must be used. The remote modem
constantly sends back information about the demodulator E
b
/N
0
using reserved bytes in the
overhead structure. The local modem then compares this value of E
b
/N
0
with a pre-defined target
value. If the Remote E
b
/N
0
is below the target, the local modem will increase its output power,
and hence, a closed-loop feedback system is created over the satellite link. A particularly
attractive benefit of this feature is that whenever framed operation is selected, the remote
demodulator’s E
b
/N
0
can be viewed from the front panel display of the local modem.
There are several important parameters associated with this mode of operation; the user needs to
understand how the AUPC feature works, and the implications of setting these parameters.
8.2 Setting AUPC Parameters
1. Under the menu (CONFIG: FRAME), the user must first ensure that the framing type is
EDMAC or EDMAC-2.
(EDMAC or EDMAC-2 may be configured as IDLE, or the unit may be defined as an EDMAC
Master or Slave.)
2. The user should verify that the remote modem is correspondingly configured for EDMAC or
EDMAC-2 framing.
3. Under the menu (CONFIG: TX Æ Pwr), the user sets the nominal output power of the
modem. This is done by selecting the Output Power Level Mode on this menu screen as
MANUAL, then editing the displayed Tx output power level.
WARNING