Professor Sorina Dumitrescu
Bit-error Resilient Index Assignments for Multiple Description Scalar Quantizers
A multiple description (MD) code generates several descriptions of a signal such that the quality of the reconstruction increases with the number of decoded descriptions. MD coding ﬁnds applications in the transmission of multimedia signals over wired or wireless networks as it enables graceful recovery from losses in situations when retransmission is not an option due to stringent delay constraints. While conventional MD codes are built only for robustness against description loss it has been observed that the redundancy present in the system can also be used to mitigate the effect of bit errors. The general problem addressed in this talk is to increase the bit-error resilience of existing MD codes. For this, we consider a two-description scalar quantizer and we apply a permutation to the set of indices of each description to increase the minimum Hamming distance (dmin) of the set of valid index pairs. First we address the existence and construction of permutations achieving dmin ≥ 2 by establishing the connection with the hypercube antibandwidth problem. Next we show how to construct linear permutations that achieve dmin ≥ 3. Further, we consider the case when one description is known to be correct and show how to obtain linear permutations achieving a minimum side Hamming distance of at least d based on linear block channel codes of Hamming distance d + 1. Additionally, we highlight the relation between the error robustness at the side decoders and the bandwidth of the hypercube labeling associated to the permutation. In order to increase the error resilience at both the central and side decoders we construct a class of hypercube labelings trading the increase in antibandwidth for the decrease in bandwidth.
Sorina Dumitrescu received the M.A.Sc. and Ph.D. degrees in mathematics from the University of Bucharest, Romania, in 1990 and 1997, respectively. From 2000 to 2002 she was a Postdoctoral Fellow in the Department of Computer Science at the University of Western Ontario, London, Canada. Since 2002 she has been with the Department of Electrical and Computer Engineering at McMaster University, Hamilton, Canada, where she held a postdoctoral position (2002-2004), a Research Associate position (2004-2005), and an Assistant Professor position (2005-2011), and where she is currently an Associate Professor. Her current research interests include multimedia coding and communications, robust image coding, network-aware data compression, multiple description codes, quantization, joint source-channel coding, steganalysis. Her earlier research interests were in formal languages and automata theory. Dr. Dumitrescu held an NSERC University Faculty Award during April 2007-March 2012.
Invited by Professor En-Hui Yang