SHAPING THE FUTURE OF SATELLITE COMMUNICATIONS
8.1.3.3 DVB-S2 CCM, VCM and ACM
CCM
In DVB-S2 each Baseband frame can be modulated with different error correction
and modulation parameters (in short, ModCod, for example QPSK 4/5). A DVB-S2
modulator is capable of detecting these parameters on the flight, without loosing
synchronization from one frame to the next.
When the same parameters are used for all frames of the DVB-S2 carrier, the
mode of operation is called CCM (Constant Coding and Modulation).
A DVB-S2 CCM uplink signal must be dimensioned according to the smallest
receiving station and the higher possible signal fading, to ensure adequate signal
availability in all receiving stations.
Figure 61- CCM
Auto-CCM is a demodulation capability that indicates that the demodulator can
automatically detect the coding and modulation parameters used by the modulator
operating in CCM mode. The advantage of auto-CCM compared to CCM, is that
auto-CCM does not require the knowledge and configuration of the ModCod on the
demodulator (plug-and-play configuration).
VCM
Variable Coding and Modulation is a mode of operation that allows different
modulations parameters to be applied to the different DVB-S2 streams of a multi-
stream signal. If each of the stream is intended for a different receiving site, VCM
allows optimizing the parameters of each stream to be optimized for each receive
station, instead of dimensioning the whole link according to the smallest station.
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