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Protograph Based LDPC Codes with Minimum Distance Linearly Growing with Block Size

Speakers: Dariush Divsalar and Chris Jones, Jet Propulsion LaboratoryAbstract: We propose several LDPC code constructions that simultaneously achieve good threshold and error floor performance. By considering ensemble average weight enumerators, minimum distance is shown to grow linearly with block size (similar to regular codes of variable degree at least 3). Our constructions are based on projected graph, or protograph, structures that support high-speed decoder implementations. As with irregular ensembles, our constructions are sensitive to the proportion of degree-2 variable nodes. A code with too few such nodes tends to have an iterative decoding threshold that is far from the capacity threshold while a code with too many such nodes tends to not exhibit a minimum distance that grows linearly in block length. In this paper we also show that precoding can be used to lower the threshold of regular LDPC codes. A family of low to high rate codes with minimum distance linearly increasing in block size and with capacity approaching performance thresholds is presented. FPGA simulation results for a few example codes show that the proposed codes perform as predicted. Encoders for the proposed codes will be discussed.Research presented is the work of D. Divsalar, C. Jones, S. Dolinar, and J. Thorpe of Jet Propulsion Laboratory, California Institute of Technology.Bios: Dariush Divsalar received Ph.D. degree in EE from UCLA in 1978. Since then, he has been with the Jet Propulsion Laboratory, California Institute of Technology, where he is a principal scientist. During past 20 years, he taught graduate courses at UCLA and Caltech. He has published over 150 papers, coauthored three books and holds ten U.S. patents in the above areas. Recently, one of his papers has been selected as one of the key research papers published by the IEEE Communications Society during the past five decades. He has received over 25 NASA Tech Brief awards and a NASA Exceptional Engineering Achievement Medal in 1996. He served as Editor for the IEEE Transactions on Communications from 1989 to 1996. Dr. Divsalar is a Fellow of IEEE.Christopher R. Jones received BS, MS, and Ph.D. degrees in Electrical Engineering from UCLA in 1995, 1996, and 2003. From 1997 to 2002 Dr. Jones worked with Broadcom Corporation in the area of VLSI architectures for communications systems. Since Jan. 2004 he has been with the Jet Propulsion Laboratory where he works on problems related to modulation, code design, hardware architectures for encoding/decoding, synchronization, and modulation. Dr. Jones has published a combination of 40 papers and patents.Host: Professor Giuseppe Caire, caire@usc.edu, x.04683

Location: Hughes Aircraft Electrical Engineering Center (EEB) - -248

Audiences: Everyone Is Invited

Contact: Mayumi Thrasher