Correcting suboptimal metrics in iterative decoders

A. Alvarado, V. Nunez, L.L. Szczecinski, E. Agrell

Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

12 Citations (Scopus)


In this paper the issue of improving the performance of iterative decoders based on sub-optimal calculation of the messages exchanged during iterations (L-values) is addressed. It is well known in the literature that a simple-yet very effective-way to improve the performance of suboptimal iterative decoders is based on applying a scaling factor to the L-values. In this paper, starting with a theoretical model based on the so-called consistency condition of a random variable, we propose a methodology for correcting the L-values that relies only on the distribution of the soft information exchanged in the iterative process. This methodology gives a clear explanation of why the well-known linear scaling factor provides a very good performance. Additionally, the proposed methodology allows us to avoid the exhaustive search required otherwise. Numerical simulations show that for turbo codes the scaling factors found closely follow the optimum values, which translates to a close-to-optimal BER performance. Moreover, for LDPC codes, the proposed methodology produces a better BER performance compared with the known method in the literature.
Original languageEnglish
Title of host publicationIEEE International Conference on Communications (ICC) 2009
Place of PublicationPiscataway
PublisherInstitute of Electrical and Electronics Engineers
ISBN (Print)978-1-4244-3435-0
Publication statusPublished - Jun 2009
Event2009 IEEE International Conference on Communications (ICC 2009) - Dresden, Germany
Duration: 14 Jun 200918 Jun 2009


Conference2009 IEEE International Conference on Communications (ICC 2009)


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