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opensand:emulated_satcom_features:physical:ccm:index

# Constant Coding and Modulation (CCM)

Constant Coding and Modulation (CCM) is one of the three coding and modulation schemes for the forward link implemented in OpenSAND.

With CCM, the MODCOD used to encode the packets is constant during the emulation.

## OpenSAND Exploitation

CCM is not the default mode of operation in OpenSAND. However, it can be enabled for each forward link carrier from the OpenSAND Manager.

To do so, in the Carrier configuration window, click on the Configure button under the MODCOD label. This will open a new window, where the different coding and modulation schemes can be selected. Select CCM in the left box, and the available MODCODs will be shown at the right. Unlike ACM and VCM, where you may select more than one MODCOD, in CCM exactly one MODCOD has to be selected.

## OpenSAND Software Design

In the OpenSAND core, CCM is implemented as a particular case of VCM, with only one MODCOD selected. Refer to the VCM implementation section for more information.