Faculty of Engineering and Natural Sciences
LDPC convolutional codes: What are they? How do they work? Are they any good?
Ali Emre Pusane
LDPC convolutional codes have been shown to be capable of achieving the same capacity-approaching performance as LDPC block codes with iterative message passing decoding. In this talk, we present several methods of deriving families of time-varying and time-invariant LDPC convolutional codes from LDPC block codes. We demonstrate that the derived LDPC convolutional codes significantly outperform the underlying LDPC block codes, and we investigate the reasons for these "convolutional gains".
In particular, we analyze the pseudo-weight spectra of the LDPC convolutional codes and show that the minimum free pseudo-weight of the convolutional code is at least as large as the minimum pseudo-weight of the underlying block code, in both the time-varying and time-invariant cases. We also prove that the unwrapped LDPC convolutional codes have better graph-cycle properties. These facts lead to significantly improved BER performance at low-to-moderate SNRs for the convolutional codes, a conclusion supported by simulation results. Finally, we use asymptotic methods to calculate a lower bound on the free distance that grows linearly with constraint length for several ensembles of unterminated, protograph-based periodically time-varying LDPC convolutional codes. We show that the free distance growth rates of the LDPC convolutional code ensembles exceed the minimum distance growth rates of the corresponding LDPC block code ensembles.
Ali Emre Pusane was born in Istanbul, Turkey in 1978. He received his B.Sc. and M.Sc. degrees in Electronics and Communications Engineering from Istanbul Technical University, Istanbul, Turkey, in 1999, and 2002, respectively. He received an M.Sc. degree in Electrical Engineering in 2004, another M.Sc. degree in Applied Mathematics in 2006, and a Ph.D. degree in 2008 from the University of Notre Dame, Notre Dame, IN. He is currently a Visiting Assistant Professor in the Department of Electrical Engineering at the University of Notre Dame.
Ali Pusane is the recipient of a Werner von Siemens Excellence Award for his M.Sc. studies at Istanbul Technical University. He also received a Best Student Paper Award with his paper entitled "Power control for orthogonal space-time coding with multiple receive antennas" presented at the 10th IEEE Signal Processing and Communication Applications Conference. He was a Summer Fellow of the Center for Applied Mathematics at the University of Notre Dame in summer 2004, and a Graduate Fellow of the same center for the 2006-2007 academic year. He is a member of the Institute of Electrical and Electronics Engineers (IEEE) and serves to several IEEE journals and conferences as a reviewer.
Dec. 30, 14:00, FENS L027