Open Access

A Theoretical Framework for Soft-Information-Based Synchronization in Iterative (Turbo) Receivers

  • Nele Noels1Email author,
  • Vincenzo Lottici2,
  • Antoine Dejonghe3,
  • Heidi Steendam1,
  • Marc Moeneclaey1,
  • Marco Luise2 and
  • Luc Vandendorpe3
EURASIP Journal on Wireless Communications and Networking20052005:576206

DOI: 10.1155/WCN.2005.117

Received: 13 May 2004

Published: 28 April 2005

Abstract

This contribution considers turbo synchronization, that is to say, the use of soft data information to estimate parameters like carrier phase, frequency, or timing offsets of a modulated signal within an iterative data demodulator. In turbo synchronization, the receiver exploits the soft decisions computed at each turbo decoding iteration to provide a reliable estimate of some signal parameters. The aim of our paper is to show that such "turbo-estimation" approach can be regarded as a special case of the expectation-maximization (EM) algorithm. This leads to a general theoretical framework for turbo synchronization that allows to derive parameter estimation procedures for carrier phase and frequency offset, as well as for timing offset and signal amplitude. The proposed mathematical framework is illustrated by simulation results reported for the particular case of carrier phase and frequency offsets estimation of a turbo-coded 16-QAM signal.

Keywords

turbo synchronization iterative detection turbo codes parameter estimation

Authors’ Affiliations

(1)
Department of Telecommunications and Information Processing, Ghent University
(2)
Department of Information Engineering, University of Pisa
(3)
Communications and Remote Sensing Laboratory, Université Catholique de Louvain

Copyright

© Noels et al. 2005

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.