SatX/SE300—
ACM - Adaptive Coding and Modulation
Proprietary and Confidential
122
F
IGURE
96
-
MCT
M
ODE
C
ONNECTION ON
P
OINT
-
TO
-P
OINT
F
IGURE
97-
MCT
M
ODE
C
ONNECTION ON
P
OINT
-
TO
-M
ULTIPOINT
The return channel from the receiver(s) to the transmitter is an IP link or utilizing the OTA mechanism.
The receiver signals its status to the transmitter every few seconds using the UDP protocol.
6.3.3
Output Level Mode
6.3.3.1
Constant Power Mode
In Constant Power Mode, the Modulator has the same output power but the peak to average keeps
changing when constellations change even on a frame-by-frame basis. Thus the input back-off in the
satellite is not constant. This is the suitable ACM mode for a linear satellite link that is not saturated.
The Back-off is measured as the average power of the signal vs. the saturation level of the TWTA.
Therefore when we work in constant power, the Back-off is fixed.
ACM signaling via IP link (Internet) or OTA
ACM signaling
Via IP link
(Internet) or
OTA