Patent ID: 6662337
Filing Date: 2003-12-09
Classification: H04L

Abstract:
A digital transmission system, comprising:a coder for coding an input signal with an error checking or error correcting code, an interleaver for interleaving the bits of the coded signal, a mapper for mapping the interleaved coded signal into a multilevel signal, and a transmitter for sending the multilevel signal over a noisy channel in a transmission medium; a receiver for receiving the multilevel signal distorted by noise (noisy multilevel signal), a demapper having a first input for receiving the noisy multilevel signal and operative to provide a soft demapped signal at an output a deinterleaver, for deinterleaving the demapped signal, a decoder to decode the deinterleaved demapped signal to provide a soft decoded signal, an interleaver to interleave the decoded signal, the demapper having a second input for receiving the interleaved decoded signal and being operative to recalculate the demapped signal iteratively using the noisy signal and the soft decoded signal, characterized bye: a mapping store for storing two different mappings having different mutual information; means for deriving an indication of the channel conditions; means for selecting t e mappings in a mixing ratio dependent on the derived indication of channel conditions, the mapper and demapper being operatively responsive to the selected mapping.