On the Asymptotic Performance of Bit-Wise Decoders for Coded Modulation
Mikhail Ivanov, Alex Alvarado, Fredrik Brannstrom, Erik Agrell

TL;DR
This paper analyzes the asymptotic performance of bit-wise decoders in coded modulation, showing a bounded loss compared to maximum likelihood decoding, with zero loss for many linear codes over Gaussian channels.
Contribution
It provides a theoretical analysis of the asymptotic loss of bit-wise decoders, quantifying the maximum loss and identifying conditions for zero loss.
Findings
Asymptotic loss bounded by 1.25 dB for any code
Zero asymptotic loss for many linear codes over Gaussian channels
Performance gap between decoders is limited at high SNR
Abstract
Two decoder structures for coded modulation over the Gaussian and flat fading channels are studied: the maximum likelihood symbol-wise decoder, and the (suboptimal) bit-wise decoder based on the bit-interleaved coded modulation paradigm. We consider a 16-ary quadrature amplitude constellation labeled by a Gray labeling. It is shown that the asymptotic loss in terms of pairwise error probability, for any two codewords caused by the bit-wise decoder, is bounded by 1.25 dB. The analysis also shows that for the Gaussian channel the asymptotic loss is zero for a wide range of linear codes, including all rate-1/2 convolutional codes.
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Taxonomy
TopicsAdvanced Wireless Communication Techniques · Error Correcting Code Techniques · Wireless Communication Security Techniques
