Séminaire Iryna Andriyanova, directrice du département info de l’ENSEA de Cergy-Pontoise
In this talk we will focus on distributed storage (DS) for a wireless network where mobile devices arrive and depart according to a Poisson 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.
Two following aspects will be considered within the aforementioned model:
- The repair problem in a single-cell scenario in which the repair process is scheduled periodically with some interval t. We derive analytical expressions for the overall communication cost in the network as a function of the repair interval t and show 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 coded caching and placement problem in a multiple-cell scenario when the devices move from one cell to another without leaving the geographical area covered by the cells (i..e., no repair is needed). We derive a good approximation of the distribution of caching devices within the communication range of mobile devices at any given time and then we optimize the maximum distance separable (MDS) codes to minimize the network load under a cache size constraint and show that using optimized MDS codes results in significantly lower network load compared to when caching the most popular files. Finally, we give a numerical evidence that caching coded symbols of each file on all mobile devices, i.e., maximal spreading, is optimal.
This is a joint work with J. Pedersen, A. Graell i Amat and F. Brannstrom from the Chalmers University of Technology, Sweden.
Iryna Andriyanova (S’03–M’07) received the M.Sc. degree in Electrical Engineering from the National Polytechnic University of Odessa, Ukraine, in 2002, and the M.Sc. and Ph.D. degrees in communication systems from Telecom ParisTech, Paris, France, in 2003 and 2006, respectively. From 2003 to 2006, she was a Research Engineer with Orange Laboratories, Rennes, France. From 2007 to 2008, she was a Post-Doctoral Research Assistant with the Federal Polytechnic School of Lausanne, Switzerland. In 2009, she joined the ETIS UMR8051 Laboratory, University of Paris-Seine, ENSEA, University of Cergy-Pontoise, CNRS, Cergy-Pontoise, France, where she is currently an Associate Professor and Director of the Department of Computer Sciences. Her research interests include coding theory and techniques, distributed storage, and wireless networks.