On the Asymptotic Performance of Bit-Wise Decoders for Coded Modulation

摘要

Two decoder structures for coded modulation over the Gaussian and flat fadingchannels are studied: the maximum likelihood symbol-wise decoder, and the(suboptimal) bit-wise decoder based on the bit-interleaved coded modulationparadigm. We consider a 16-ary quadrature amplitude constellation labeled by aGray labeling. It is shown that the asymptotic loss in terms of pairwise errorprobability, for any two codewords caused by the bit-wise decoder, is boundedby 1.25 dB. The analysis also shows that for the Gaussian channel theasymptotic loss is zero for a wide range of linear codes, including allrate-1/2 convolutional codes.