tailieunhanh - Báo cáo hóa học: " A Theoretical Framework for Soft-Information-Based Synchronization in Iterative (Turbo) Receivers"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: A Theoretical Framework for Soft-Information-Based Synchronization in Iterative (Turbo) Receivers | EURASIP Journal on Wireless Communications and Networking 2005 2 117-129 2005 Hindawi Publishing Corporation A Theoretical Framework for Soft-Information-Based Synchronization in Iterative Turbo Receivers Nele Noels 1 Vincenzo Lottici 2 Antoine Dejonghe 3 Heidi Steendam 1 Marc Moeneclaey 1 Marco Luise 2 Luc Vandendorpe3 1 Department of Telecommunications and Information Processing Ghent University 9000 Gent Belgium Emails nnoels@ hs@ mm@ 2 Department of Information Engineering University of Pisa 56122 Pisa Italy Emails 3 Communications and Remote Sensing Laboratory Universite Catholique de Louvain 1348 Louvain-la-Neuve Belgium Email dejonghe@ vandendorpe@ Received 13 May 2004 Revised 29 September 2004 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 and phrases turbo synchronization iterative detection turbo codes parameter estimation. 1. INTRODUCTION The impressive performance of turbo codes 1 has triggered in the last decade a lot of research addressing the application of