Talk: Alexandre Graell i Amat (October 28, 2015 at 02:30 pm, LNT Seminar Room N2408)


On October 28, 2015 at 02:30 pm, Alexandre Graell i Amat from Chalmers University of Technology will be giving a talk in the LNT Seminar Room N2408 about "Wireless Distributed Storage with Device-to-Device Communication".

Wireless Distributed Storage with Device-to-Device Communication

Alexandre Graell i Amat

Chalmers University of Technology
Department of Signals and Systems


We consider distributed storage (DS) for a wireless network where mobile devices arrive and depart according to a random process. Content is stored in a number of mobile devices, using an erasure correcting code. When requesting a piece of content, a user retrieves the content from the mobile devices using device-to-device communication or, if not possible, from the base station (BS), at the expense of a higher communication cost. We consider the repair problem when a device that stores data leaves the network. In particular, we introduce a repair scheduling where repair is performed (from storage devices or the BS) periodically. We derive analytical expressions for the overall communication cost of repair and download as a function of the repair interval. We illustrate the analysis by giving results for maximum distance separable codes, regenerating codes and locally repairable codes. Our results indicate that DS can reduce the overall communication cost with respect to the case where content is only downloaded from the BS, provided that repairs are performed frequently enough. The required repair frequency depends on the code used for storage and the network parameters. In particular, minimum bandwidth regenerating codes require frequent repairs, while maximum distance separable codes and locally repairable codes give better performance if repair is performed less frequently.


Alexandre Graell i Amat received the PhD degree from the Politecnico di Torino, Turin, Italy in 2004. From September 2001 to May 2002, he was a Visiting Scholar at the University of California San Diego, CA, USA. From 2001 to 2004, he held a part-time Appointment at STMicroelectronics Data Storage Division, Milan, Italy, as consultant on coding for magnetic recording channels. From March 2004 to December 2005, he was a Visiting Professor at the Universitat Pompeu Fabra, Barcelona, Spain. From January 2006 to December 2010, he was with the Department of Electronics, TELECOM Bretagne (former ENST Bretagne), Brest, France, first as a Postdoc and since October 2008 as an Associate Professor. In January 2011, he joined the Department of Signals and Systems, Chalmers University of Technology, Gothenburg, Sweden, where he is currently an Associate Professor. His research interests include modern coding theory, distributed storage and optical communications. He is currently an Associate Editor of the IEEE TRANSACTIONS ON COMMUNICATIONS and was an Associate Editor of the IEEE COMMUNICATIONS LETTERS (2011–2013). He was the General Co-Chair of the 7th International Symposium on Turbo Codes and Iterative InInformation Processing, Gothenburg, Sweden, August 2012. He received the Marie Curie Intra-European Fellowship from the European Commission and was awarded the "IEEE Communications Society 2010 Europe, Middle East, and Africa Region Outstanding Young Researcher Award".