The new researchers sign their first paper as Gradiant team members

One of the most important part of the research is to publish papers, either in the sector magazines or in the specialized events. Three of the Gradiant researchers have received these days the new of the publication of their respective papers.

Luis Pérez, Researcher-Coordinator and Miguel Rodelgo and David Chaves, both Researchers and Project Manager, have received the new of the publication of their papers in scientific magazines and in an event, both with an international level.

“Spread-Spectrum Watermarking Security” Luis Pérez Freire and Fernando Pérez González are the authors of this paper, that will be published in the magazine IEEE Transactions on Information Forensics and Security ( This paper presents a rigorous approach to the security of digital watermarking methods based on spread spectrum, the most widely adopted watermarking technique. In a theoretical plane, the security of such methods is objectively analyzed in an information-theoretic manner, quantifying the information leakage about the secret key, which can be exploited by an attacker. On the practical side, the performance of previously existent methods for key estimation is quantified, and new methods are proposed based on the blind equalization paradigm, inspired on the field of digital communications. The paper is part of Luis Pérez Freire Ph.D. thesis, devoted to the formalization and analysis of the security problem in digital watermarking.

“Practical Scalability of Wavelength Routing Switches”

In this case, the paper is the result of the collaboration between Gradiant and the University of New York. This is the paper of Miguel Rodelgo Lacruz and will be performed in the IEEE International Conference on Communications 2009 (IEEE ICC 2009, the 14th-18th of June in Dresden (Germany). Miguel Rodelgo shares the author with F. Javier González Castaño, Reasearch Director in Gradiant, C. López Bravo, from Telematic Engineering Department of University of Vigo and H. Jonathan Chao, from Dept. of Electrical and Computer Engineering, Polytechnic Institute of NYU, United States of America).

The paper is a study about the practical scalability of Arrayed Waveguide Gratings (AWGs)-based electro-optical switches for the future core networks. AWG is a passive optical device whose insertion losses do not depend on number of ports. However, accurate second order assessment has demonstrated that in-band crosstalk exponentially increases the power penalty, limiting the realistic useful size of AWG commercial devices to less than 20 ports for all bit rates. On the other hand, the in-band crosstalk at AWG outputs depends on the connection pattern set by the scheduling algorithm and this port count limitation is calculated for the worst case. In the paper, we show that distributed schedulers with predetermined connections patterns can avoid these harmful arrangements and we calculate the best connection patterns taking into account the crosstalk penalty. We also show that the probability of worst case patterns is very low and we can find a more realistic limit for general centralized schedulers assuming losses with probability far below the objective BER. With these results, we calculate more realistic port count limits for both scheduler types.

“Integration of Nomadic Devices with Automotive User Interfaces” This is the paper of David Chaves, co-author with Felipe Gil and F. Javier González Castaño and will be published in the “IEEE Transactions on Consumer Electronics” in the number of febrary. In this paper, a new model for Web 2.0 information migration to automotive embedded devices is proposed. This model takes the most of Web 2.0 user-friendly interfaces, through the use of nomadic information transmission systems. As a result, in-vehicle interaction between user and embedded devices can be reduced, also avoiding the need for a permanent data connection to send data from user’s personal computer to his car. The paper also describes a implementation of this type of system, as a proof-of-concept of the topics mentioned above.