فارسی English
Network codes, rateless codes, and their belief propagation decoders

دکتر یوسفی،
دانشگاه کوئینز کانادا

In today’s telecom applications, content can originate from multiple sources and may travel through many transport nodes and multiple hops to reach one or more receivers. This is a common scenario in multimedia dissemination applications, sensor networks, and peer to peer networks (P2P) such as those based on Microsoft’s Avalanche protocol. Currently, intermediate nodes in a communications network perform buffer-and-forward (BF). This is not an optimal strategy in the sense of overall network throughput. Network coding (NC) and rateless coding (RC) methods have been proposed to allow for closer to optimal operation of wired as well as wireless networks. These are tantamount to a shift in paradigm: nodes need to encode-and-forward rather than simply buffer-and-forward. In this talk, we will compare NC and RC in terms of implementation, performance, and complexity. A few architectures and scenarios will be discussed. Some of the protocols presented are the most efficient known today. Are these NC- or RC-based schemes?
In RC- and NC-based systems alike, a key enabling requirement is the availability of low-complexity decoding algorithms. Belief Propagation (BP) algorithm is the de facto standard decoder for most graph codes. In the other part of this workshop, we turn our attention to low-complexity decoding of these and other capacity-achieving codes such as Low-Density Parity-Check (LDPC) codes. These codes generally suffer from significant error performance degradation at low error rates due to the existence of special sub-graphs such as near-codewords, pseudo-codewords, stopping sets, trapping sets, and absorbing sets. We will review and discuss these notions, their relations, and their effects on the error rates over a variety of channels such the Binary Erasure Channel (BEC), Binary Symmetric Channel (BSC), and the Binary-Input Additive White Gaussian Channel (BIAWGN).


Bio:
Shahram Yousefi received his B.Sc. in Electrical Engineering from University of Tehran, Iran. Having worked in industry for a few years, in Sept. 1997, he joined the Department of Electrical and Computer Engineering of University of Waterloo in Canada where he received his PhD in Sept. 2002. In Oct. 2002, he joined Edward S. Rogers Sr. Department of Electrical and Computer Engineering of University of Toronto, Canada and since Jan. 2003 he has been with the Department of Electrical and Computer Engineering of Queen's University, Kingston, Canada, where he is currently a tenured Associate Professor. Shahram was an invited professor at Ecole Polytechnique Fédéral de Lausanne (EPFL), Switzerland from July 2009 to June 2010. He is currently the Undergraduate Chair of Electrical Engineering program at Queen's and the Chair of IEEE Kingston Section. He is a senior member of the Institute of Electrical and Electronics Engineers (IEEE) and a Professional Engineer (P.Eng.) with the PEO of Canada and currently serves as the co-Editor-in-Chief of the Canadian Journal of Electrical and Computer Engineering (CJECE on IEEE Xplore) and an Associate Editor for the IEEE journal Communications Letters.
His research interests are mainly in the physical layer: error control, signal design, and transceiver design for high-speed high-fidelity telecom networks. Prof. Yousefi is the recipient of 42 teaching, research, and service awards including the latest Discovery Accelerator Supplement (DAS) from Natural Sciences and Engineering Research Council
(NSERC) of Canada in Apr. 2010. The DAS citation includes as the basis of the selection: “providing substantial and timely additional resources to accelerate progress, and maximize the impact of outstanding research programs.”
http://www.ece.queensu.ca/People/S-Yousefi/
بیستمین کنفرانس مهندسی برق ایران

ICEE 2012، تهران، ایران