Codes for Distributed Storage — Asking More of an Old Friend
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Department of Electrical Communication Engineering, Indian Institute of Science

2014 ISIT Plenary Lecture
Codes for Distributed Storage -- Asking More of an Old Friend
P. Vijay Kumar
Indian Institute of Science



Given the explosive growth in the amount of data that keeps getting generated and the inescapable mortality of a storage device, there is renewed interest within the storage industry in identifying techniques that will enable data to be stored in a manner that is efficient, reliable and which provides easy access to the data. Codes for distributed storage place data across nodes in a network in a redundant fashion and are designed precisely with these objectives in mind. This talk will focus on two recent approaches to code design that attempt to overcome the shortcomings of prevalent coding schemes that are based either on replication or the use of Reed-Solomon codes.
The first approach makes use of a class of codes known as regenerating codes, where the emphasis is on low storage overhead and minimization of the amount of data download needed for the repair of a failed node. Codes employed under the second approach are termed as locally repairable codes and here, the focus is on sharply reducing the number of nodes accessed during node repair. Both approaches call for additional structure within a block code and introduce new performance measures. We will overview these recent exciting developments in coding theory highlighting some of the innovative ideas that have been put forward, discuss applications, and make connections with other research topics of interest to the information-theory community.


P. Vijay Kumar received his B.Tech degree from IIT Kharagpur in 1977, his M.Tech degree from IIT Kanpur in 1979 and the Ph.D. degree from USC in 1983, all in electrical engineering. Between 1983-2003, he was a full-time faculty member of the EE-Systems Department of USC. Since 2003, he has been at the Indian Institute of Science where he is currently chairman of the Department of Electrical Communication Engineering as well as holder of the TATA Chem Chaired Professorship. Since 2010, he has also concurrently held the title of Adjunct Researcher Professor at USC. From 1993-96 Professor Kumar was an Associate Editor for Coding Theory for the IEEE Transactions on Information Theory. A 1994 paper co-authored by him showed that the apparent linear behavior of the nonlinear, binary Kerdock and Preparata codes could be explained by showing these codes to be images under the Gray map, of a pair of linear and dual Z4 codes. For this work, he received the 1994 USC School-of-Engineering's Senior Research Award as well as the 1995 IEEE Information Theory Society's Prize Paper Award. His other notable research results include co-authoring a low-complexity construction of algebraic-geometric codes achieving the Gilbert-Varshamov bound, the first explicit construction of space-time codes achieving the diversity-multiplexing gain tradeoff, as well as explicit constructions of optimal codes for distributed storage. His research interests also include wireless sensor networks where he is co-recipient of a best paper award at the Conference on Distributed Computing in Sensor Systems (DCOSS 2008). His most recent work deals with codes for distributed storage and on this topic, a recent paper co-authored by him, was awarded the IEEE Data Storage Best Paper/Best Student Paper Award of 2011/2012. A pseudorandom sequence family designed in a 1996 paper co-authored by him, now forms the short scrambling code of the 3G WCDMA cellular standard. He is an IEEE Fellow and on the ISI list of highly cited authors. He has been on the Board of Governors of the IEEE Information Theory Society since 2013 and is a TPC Co-Chair of the upcoming 2015 IEEE International Symposium on Information Theory to be held in Hong Kong.