Reduced complexity APP for turbo equalization

Dan Raphaeli*, Ami Saguy

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

10 Scopus citations


This paper investigates the subject of reducing the complexity of turbo equalization in which a receiver combines the equalization and decoding process in an iterative fashion. We show that it is possible to approximate the a posteriori probability (APP) module by two time varying linear transversal filters and a simple non-linear memoryless processor, and thus replace the exponential complexity of the APP module with quadratic complexity in the filters length. Further complexity reduction leads to linear complexity, for which the transversal filters are constant during the block. For this structure, which is similar to a previously suggested scheme, we calculate the optimized parameters and increase performance. The derivations cover the cases of BPSK and QAM modulations. Simulation results are presented for parallel-concatenated turbo code with BPSK and QAM modulation over channels that introduce severe amplitude distortion.

Original languageEnglish
Pages (from-to)1940-1943
Number of pages4
JournalConference Record - International Conference on Communications
StatePublished - 2002
Event2002 International Conference on Communications (ICC 2002) - New York, NY, United States
Duration: 28 Apr 20022 May 2002


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