variable coding and modulation (VCM)

In Adaptive Coding and Modulation( ACM), the receiver sends feedback to the transmitter indicating the transmission quality. However, there are two other methods that work without feedback: Constant Coding and Modulation( CCM) and Variable Coding and Modulation( VCM).

In the VCM method, the transmission parameters are dynamically adapted to the available bandwidth depending on the priority of the input data.

The VCM method is used in Standard Definition Television( SDTV) and is much more robust than the services of HDTV.