Speaker:Professor Jean-François Hélard

Date:April 12, 2013

Time:2:00 p.m.

Location:Lecture Hall of the School of Information Science and Engineering

Sponsor:School of Information Science and Engineering

Abstract:The current air interface of 4G Long Term Evolution (LTE) and most of the broadcasting digital television and wireless standards are based on multicarrier modulations such as Orthogonal Frequency Division Multiplexing (OFDM). In this tutorial, we first explain the main principles of this technique and why it works so well in presence of frequency and time selective radio mobile channels. We survey the underlying construction technique of the transmitted signal, the addition of a guard interval (Cyclic Prefix OFDM, Zero Padding OFDM), the interest of the combination with channel coding, the differential and coherent demodulation of the received signal. Then, we see how to choose the parameters of such systems and will present the performance in frequency and time selective channels. Peak power problem and implementation issues will be also addressed. Finally, some examples of applications of multicarrier modulations in the field of Digital Video Broadcasting (DVB-T/DVB-T2/DVB-NGH, DMB-T) and of cellular networks (LTE/LTE-A) will be presented.

Professor Jean-François Hélardreceived his Dipl.-Ing. and his Ph.D in electronics and signal processing from the National Institute of Applied Sciences (INSA) in Rennes, France, in 1981 and 1992, respectively. From 1982 to 1997, he was research engineer and then head of channel coding for the digital broadcasting research group at France Telecom Research Center in Rennes. In 1997, he joined INSA, where he is currently Professor and Director of Research INSA Rennes. He is also Deputy Director of the Joint Research Unit UMR IETR (Institute of Electronics and Telecommunications in Rennes), created in 2002 in association with the CNRS and University of Rennes 1. His research interests lie in signal processing techniques for digital communications, such as space-time and channel coding, multi-carrier modulation, multi-user communications, resource allocation, spectrum and energy efficient techniques... He is involved in several European and national research projects in the fields of digital video terrestrial broadcasting, mobile radio communications and cellular networks, power-line and ultra-wide-band communications, cooperative communications and relaying techniques. Prof. J-F. Hélard is a senior member of IEEE, author and co-author of more than 200 technical papers in international scientific journals and conferences, and holds 14 European patents.

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