Patent ID: 6536010
Filing Date: 2003-03-18
Classification: H03M,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 by: a mapping store for storing a plurality of different mappings; means for deriving an indication of the channel conditions; and means for selecting the optimum mapping of the plurality dependent on the derived indication of channel conditions, the mapper and demapper being operatively responsive to the selected mapping.