Transmission system using block-coded or trellis-coded modulations, receiver and decoder for such a system

摘要

A decoder for a series of received digital signal samples which are encoded as points in a 2-dimensional constellation of points corresponding to authorized code values, which constellation is sub-divided into a plurality of subsets. The branch length mu between a received point and the closest authorized point in a subset is calculated as a function of the magnitude and sign of the error distance between the received point and the closest authorized point of the constellation, and of the displacement between successive authorized points in the subsets. It is thus possible to determine branch length without calculation of squared values and without employing any approximations.