CODE MAPPING IN A TRELLIS DECODER

A trellis decoder system uses a feed-forward trellis demapping configuration to prevent error propagation. In a system for processing encoded binary data symbols representable as a symbol constellation, a decoder includes a delay for delaying received encoded symbol data. The decoder also includes a re-encoder for re-coding decoded symbol representative data and a processor for deriving decoded symbol data. The processor derives decoded symbol data using the delayed encoded symbol data and re-encoded data representative of a difference between successive symbols computed using an error propagation-free, feed-forward configuration.