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Benammar M.,CentraleSupelec | Benammar M.,Huawei | Piantanida P.,University Paris - Sud
IEEE Transactions on Information Theory | Year: 2015

This paper investigates the secrecy capacity of the wiretap broadcast channel (WBC) with an external eavesdropper where a source wishes to communicate two private messages over a broadcast channel (BC) while keeping them secret from the eavesdropper. We derive a nontrivial outer bound on the secrecy capacity region of this channel which, in absence of security constraints, reduces to the best known outer bound to the capacity of the standard BC. An inner bound is also derived, which follows the behavior of both the best known inner bound for the BC and the wiretap channel. These bounds are shown to be tight for the deterministic BC with a general eavesdropper, the semideterministic BC with a more noisy eavesdropper, and the wiretap BC where users exhibit a less noisiness order between them. Finally, by rewriting our outer bound to encompass the characteristics of parallel channels, we also derive the secrecy capacity region of the product of two inversely less noisy BCs with a more noisy eavesdropper. We illustrate our results by studying the impact of security constraints on the capacity of the WBC with binary erasure and binary symmetric components. © 2015 IEEE. Source


Molinie P.,CentraleSupelec
IEEE Transactions on Plasma Science | Year: 2015

Conduction models in disordered materials are described, with a special focus on the transient behavior appearing on a broad timescale as a consequence of disorder. Multiple trapping models, hopping models, or random walks coupled with waiting-time distributions are commonly used to describe charge transport in semiconductors. Important concepts have been introduced in this field, such as demarcation energy, percolation, or transport energy. Dispersive transport appears as a consequence of the disorder, together with a memory effect, that may be described using various mathematical tools. The interest of this research field concerning the charging behavior of materials used in spacecraft applications, especially polymers, is underlined and a practical model of the insulator is suggested. © 2015 IEEE. Source


Bjornson E.,Linkoping University | Larsson E.G.,Linkoping University | Debbah M.,CentraleSupelec | Debbah M.,Huawei
IEEE Transactions on Wireless Communications | Year: 2016

Massive MIMO is a promising technique for increasing the spectral efficiency (SE) of cellular networks, by deploying antenna arrays with hundreds or thousands of active elements at the base stations and performing coherent transceiver processing. A common rule-of-thumb is that these systems should have an order of magnitude more antennas M than scheduled users K because the users' channels are likely to be near-orthogonal when M/K > 10. However, it has not been proved that this rule-of-thumb actually maximizes the SE. In this paper, we analyze how the optimal number of scheduled users K∗ depends on M and other system parameters. To this end, new SE expressions are derived to enable efficient system-level analysis with power control, arbitrary pilot reuse, and random user locations. The value of K∗ in the large-M regime is derived in closed form, while simulations are used to show what happens at finite M, in different interference scenarios, with different pilot reuse factors, and for different processing schemes. Up to half the coherence block should be dedicated to pilots and the optimal M/K is less than 10 in many cases of practical relevance. Interestingly, K∗ depends strongly on the processing scheme and hence it is unfair to compare different schemes using the same K. © 2002-2012 IEEE. Source


Arrano H.F.,CentraleSupelec | Azurdia Meza C.A.,University of Chile
IEEE Latin America Transactions | Year: 2015

In this paper the parametric linear combination pulse (IPLCP) is proposed. The IPLCP is a new family of Nyquist-I pulses with two additional degrees of freedom to minimize the inter-carrier interference (ICI) power in orthogonal frequency-division multiplexing (OFDM) based systems due to frequency offset. Theoretical and numerical simulations are shown to verify that the performance of the IPLCP outperforms other existing pulses. © 2003-2012 IEEE. Source


Grant
Agency: Cordis | Branch: H2020 | Program: RIA | Phase: ICT-25-2015 | Award Amount: 3.44M | Year: 2015

New computing paradigms are required to feed the next revolution in Information Technology. Machines need to be invented that can learn, but also handle vast amount of data. In order to achieve this goal and still reduce the energy footprint of Information and Communication Technology, fundamental hardware innovations must be done. A physical implementation natively supporting new computing methods is required. Most of the time, CMOS is used to emulate e.g. neuronal behavior, and is intrinsically limited in power efficiency and speed. Reservoir computing (RC) is one of the concepts that has proven its efficiency to perform tasks where traditional approaches fail. It is also one of the rare concepts of an efficient hardware realization of cognitive computing into a specific, silicon-based technology. Small RC systems have been demonstrated using optical fibers and bulk components. In 2014, optical RC networks based integrated photonic circuits were demonstrated. The PHRESCO project aims to bring photonic reservoir computing to the next level of maturity. A new RC chip will be co-designed, including innovative electronic and photonic component that will enable major breakthrough in the field. We will i) Scale optical RC systems up to 60 nodes ii) build an all-optical chip based on the unique electro-optical properties of new materials iii) Implement new learning algorithms to exploit the capabilities of the RC chip. The hardware integration of beyond state-of-the-art components with novel system and algorithm design will pave the way towards a new era of optical, cognitive systems capable of handling huge amount of data at ultra-low power consumption.

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