Showing papers by "Orange S.A. published in 2007"

A review of classification algorithms for EEG-based brain–computer interfaces

Abstract: In this paper we review classification algorithms used to design brain–computer interface (BCI) systems based on electroencephalography (EEG). We briefly present the commonly employed algorithms and describe their critical properties. Based on the literature, we compare them in terms of performance and provide guidelines to choose the suitable classification algorithm(s) for a specific BCI.

PRESENT: An Ultra-Lightweight Block Cipher

Abstract: With the establishment of the AES the need for new block ciphers has been greatly diminished; for almost all block cipher applications the AES is an excellent and preferred choice. However, despite recent implementation advances, the AES is not suitable for extremely constrained environments such as RFID tags and sensor networks. In this paper we describe an ultra-lightweight block cipher, present . Both security and hardware efficiency have been equally important during the design of the cipher and at 1570 GE, the hardware requirements for present are competitive with today's leading compact stream ciphers.

PRESENT: An Ultra-Lightweight Block Cipher

Abstract: With the establishment of the AES the need for new block ciphers has been greatly diminished; for almost all block cipher applications the AES is an excellent and preferred choice. However, despite recent implementation advances, the AES is not suitable for extremely constrained environments such as RFID tags and sensor networks. In this paper we describe an ultra-lightweight block cipher, present . Both security and hardware efficiency have been equally important during the design of the cipher and at 1570 GE, the hardware requirements for present are competitive with today's leading compact stream ciphers.

Shifting the MIMO Paradigm

Abstract: Multi-user MIMO (MU-MIMO) networks reveal the unique opportunities arising from a joint optimization of antenna combining techniques with resource allocation protocols. Furthermore, it brings robustness with respect to multipath richness, allowing for compact antenna spacing at the BS and, crucially, yielding the diversity and multiplexing gains without the need for multiple antenna user terminals. To realize these gains, however, the BS should be informed with the user's channel coefficients, which may limit practical application to TDD or low-mobility settings. To circumvent this problem and reduce feedback load, combining MU-MIMO with opportunistic scheduling seems a promising direction. The success for this type of scheduler is strongly traffic and QoS-dependent, however.

Fully collusion secure dynamic broadcast encryption with constant-size ciphertexts or decryption keys

Abstract: This paper puts forward new efficient constructions for public-key broadcast encryption that simultaneously enjoy the following properties: receivers are stateless; encryption is collusion-secure for arbitrarily large collusions of users and security is tight in the standard model; new users can join dynamically i.e. without modification of user decryption keys nor ciphertext size and little or no alteration of the encryption key. We also show how to permanently revoke any subgroup of users. Most importantly, our constructions achieve the optimal bound of O(1)-size either for ciphertexts or decryption keys, where the hidden constant relates to a couple of elements of a pairing-friendly group. Our broadcast-KEM trapdoor technique, which has independent interest, also provides a dynamic broadcast encryption system improving all previous efficiency measures (for both execution time and sizes) in the private-key setting.

An Improved Vehicular Ad Hoc Routing Protocol for City Environments

Abstract: The fundamental component for the success of VANET (vehicular ad hoc networks) applications is routing since it must efficiently handle rapid topology changes and a fragmented network. Current MANET (mobile ad hoc networks) routing protocols fail to fully address these specific needs especially in a city environments (nodes distribution, constrained but high mobility patterns, signal transmissions blocked by obstacles, etc.). In our current work, we propose an inter-vehicle ad-hoc routing protocol called GyTAR (improved greedy traffic aware routing protocol) suitable for city environments. GyTAR consists of two modules: (i) dynamic selection of the junctions through which a packet must pass to reach its destination, and (ii) an improved greedy strategy used to forward packets between two junctions. In this paper, we give detailed description of our approach and present its added value compared to other existing vehicular routing protocols. Simulation results show significant performance improvement in terms of packet delivery ratio, end-to-end delay, and routing overhead.

Commutative Encryption and Watermarking in Video Compression

Abstract: A scheme is proposed to implement commutative video encryption and watermarking during advanced video coding process. In H.264/AVC compression, the intra-prediction mode, motion vector difference and discrete cosine transform (DCT) coefficients' signs are encrypted, while DCT coefficients' amplitudes are watermarked adaptively. To avoid that the watermarking operation affects the decryption operation, a traditional watermarking algorithm is modified. The encryption and watermarking operations are commutative. Thus, the watermark can be extracted from the encrypted videos, and the encrypted videos can be re-watermarked. This scheme embeds the watermark without exposing video content's confidentiality, and provides a solution for signal processing in encrypted domain. Additionally, it increases the operation efficiency, since the encrypted video can be watermarked without decryption. These properties make the scheme a good choice for secure media transmission or distribution

Distributed Adaptive Power Allocation for Wireless Relay Networks

Abstract: In this paper, we consider a 2-hop wireless diversity relay network. We explore transmit power allocation among the source and relays to maximize the received signal to noise ratio (SNR) at the destination. We consider two relay protocols, "amplify and forward" (AAF) and "decode and forward" (DAF) and design the respective power allocations for both uneeded and coded systems. For a 2-hop relay system with one relay node, we derive a closed-form power allocation solution and, based on it, we propose a relay activation condition. If and only if the fading channel coefficients satisfy this condition, the relay transmits the signals to the destination; otherwise, the relay will stay in the idle state. For a system with more than one relay node, general closed-form power allocation solutions based on an exact SNR expression are difficult to derive; we hence, calculate a SNR upper bound and derive a sub-optimum power allocation solution based on this bound. The simulation results show that for a 2-hop diversity relay channel with one relay node the proposed adaptive power allocation (APA) scheme yields about 1- 2 dB SNR gains compared to the equal power allocation. This SNR gain increases monotonically as the number of relays increases

Comparing State-of-the-Art Collaborative Filtering Systems

Abstract: Collaborative filteringaims at helping usersfind itemsthey should appreciate from huge catalogues. In that field, we can distinguish user-based, item-basedand model-basedapproaches. For each of them, many options play a crucial role for their performances, and in particular the similarity function defined between users or items, the number of neighbors considered for user- or item-based approaches, the number of clusters for model-based approaches using clustering, and the prediction function used. In this paper, we review the main collaborative filtering methods proposed in the litterature and compare them on the same widely used real dataset called MovieLens, and using the same widely used performance measure called Mean Absolute Error(MAE). This study thus allows us to highlight the advantages and drawbacks of each approach, and to propose some default options that we think should be used when using a given approach or designing a new one.

Real-Time System for Adaptive Video Streaming Based on SVC

Abstract: This paper presents the integration of scalable video coding (SVC) into a generic platform for multimedia adaptation. The platform provides a full MPEG-21 chain including server, adaptation nodes, and clients. An efficient adaptation framework using SVC and MPEG-21 digital item adaptation (DIA) is integrated and it is shown that SVC can seamlessly be adapted using DIA. For protection of packet losses in an error prone environment an unequal erasure protection scheme for SVC is provided. The platform includes a real-time SVC encoder capable of encoding CIF video with a QCIF base layer and fine grain scalable quality refinement at 12.5 fps on off-the-shelf high-end PCs. The reported quality degradation due to the optimization of the encoding algorithm is below 0.6 dB for the tested sequences.

System and Transport Interface of SVC

Abstract: Scalable video coding (SVC) and transmission has been a research topic for many years. Among other objectives, it aims to support different receiving devices, perhaps connected through a heterogeneous network structure, using a single bit stream. Earlier attempts of standardized scalable video coding, for example in MPEG-2, H.263, or MPEG-4 Visual, have not been commercially successful. Nevertheless, the Joint Video Team has recently focused on the development of the scalable video extensions of H.264/AVC, known as SVC. Some of the key problems of older scalable compression techniques have been solved in SVC and, at the same time, new and compelling use cases for SVC have been identified. While it is certainly important to develop coding tools targeted at high coding efficiency, the design of the features of the interface between the core coding technologies and the system and transport are also of vital importance for the success of SVC. Only through this interface, and novel mechanisms defined therein, applications can take advantage of the scalability features of the coded video signal. This paper provides an overview of the system interface features defined in the SVC specification. We discuss, amongst other features, bit stream structure, extended network abstraction layer (NAL) unit header, and supplemental enhancement information (SEI) messages related to scalability information.

PULSE: An Adaptive, Incentive-Based, Unstructured P2P Live Streaming System

Abstract: Large-scale live media streaming is a challenge for traditional server-based approaches. To appropriately support big audiences, broadcasters must be able to allocate huge bandwidth and computational resources. The costs involved with such an infrastructure exclude all but the established content producers from exploiting the Internet as a distribution medium. Publishers of not-yet-popular content, unless they manage to properly predict their maximum audience size, will likely fail to dimension correctly their broadcast infrastructure. Peer-to-peer systems for live streaming allow the users to support content distribution by contributing their unused resources: this increases the scalability of the content distribution while reducing at the same time the economical burden on the streaming provider. This paper presents and evaluates PULSE, an unstructured mesh-based peer-to-peer system designed to support live streaming to large audiences under the arbitrary resource availability as is typically the case for the Internet. PULSE is a highly dynamic system: it constantly optimizes its mesh of data connections using a feedback-driven peer selection strategy that is based on pairwise incentives. We evaluate the behavior of PULSE under realistic scenarios via simulation and emulation, and present the advantages of our approach, namely a best-effort response to system-wide resource scarcity, high resilience to node churn, and good hop-count properties of the average data distribution paths.

Effect of Channel Uncertainty on the Mutual Information of MIMO Fading Channels

Abstract: In this paper, we study the effect of channel estimation error at the receiver on the mutual information of a multiple-input-multiple-output (MIMO) channel obeying correlated Rayleigh fading. We assume that perfect knowledge of the channel correlation is available at the receiver and find upper and lower bounds on the mutual information for Gaussian input signals. We prove that for a generic input covariance matrix, the gap between these two bounds at high transmit powers does not exceed a certain value, which depends on the number of nonzero eigenvalues of the receive correlation matrix. We also show that in a system with uncorrelated transmit antennas and correlated receive antennas and with uniform power distribution over the transmit antennas, these bounds are asymptotically tight for a large number of transmit antennas. We show that when the correlation information is available at the transmitter, the transmitting strategy that maximizes the mutual information lower bound is to transmit toward the directions of the eigenvectors of the transmit correlation matrix. We further derive upper and lower bounds on the mutual information of a MIMO multiple-access channel with imperfect channel estimation at the receiver. We also prove that when the input power at each user is uniformly distributed over its transmit antennas, the bounds on the mutual information are asymptotically tight for Gaussian input signals, and this tightness increases when the number of users increases. Numerical simulations are conducted to corroborate theoretical results.

Chronicle recognition improvement using temporal focusing and hierarchization

Abstract: This article falls under the problem of the symbolic monitoring of real-time complex systems or of video interpretation systems. Among the various techniques used for the on-line monitoring, we are interested here in the temporal scenario recognition. In order to reduce the complexity of the recognition and, consequently, to improve its performance, we explore two methods: the first one is the focus on particular events (in practice, uncommon ones) and the second one is the factorization of common temporal scenarios in order to do a hierarchical recognition. In this article, we present both concepts and merge them to propose a focused hierarchical recognition. This approach merges and generalizes the two main approaches in symbolic recognition of temporal scenarios: the Store Totally Recognized Scenarios (STRS) approach and the Store Partially Recognized Scenarios (SPRS) approach.

AnyBody: a self-organization protocol for body area networks

Abstract: Self-organization for wireless multi-hop systems can be divided into two categories: proactive cluster-based solutions and reactive on-demand solutions. Whereas the former have been studied for ad-hoc networks, the latter seem more adapted to low-energy low-traffic wireless sensor networks. We show that, despite the relative high cost to build and maintain a topology, a cluster-based approach is particularly suited for Body Area Networks. We present AnyBody, a self-organization protocol in which sensors attached to a person are grouped into clusters.

ITU-T G.729.1: AN 8-32 Kbit/S Scalable Coder Interoperable with G.729 for Wideband Telephony and Voice Over IP

Abstract: This paper describes the scalable coder - G.729.1 - which has been recently standardized by ITU-T for wideband telephony and voice over IP (VoIP) applications. G.729.1 can operate at 12 different bit rates from 32 down to 8 kbit/s with wideband quality starting at 14 kbit/s. This coder is a bitstream interoperable extension of ITU-T G.729 based on three embedded stages: narrowband cascaded CELP coding at 8 and 12 kbit/s, time-domain bandwidth extension (TDBWE) at 14 kbit/s, and split-band MDCT coding with spherical vector quantization (VQ) and pre-echo reduction from 16 to 32 kbit/s. Side information - consisting of signal class, phase, and energy - is transmitted at 12, 14 and 16 kbit/s to improve the resilience and recovery of the decoder in case of frame erasures. The quality, delay, and complexity of G.729.1 are summarized based on ITU-T results.

Lightweight code-based identification and signature

Abstract: We revisit the code-based identification protocol proposed by Stern at Crypto'93, and give evidence that the size of public keys can be dramatically reduced while preserving a high and well-understood level of security. More precisely, the public keys can be made even shorter than RSA ones (typically 347 bits), while their size is around 150 Kbits in the original scheme. This is achieved by using matrices which are double circulant, rather than purely random. On the whole, this provides a very practical identification (and possibly signature) scheme which is mostly attractive for light-weight cryptography.

User-profile based web page recommendation system and user-profile based web page recommendation method

Abstract: A web page recommendation system includes a browsing history database which contains information related to the web pages that a user browsed; a stability score calculating part which calculates stability scores that represent the stability of the user's web page browsing tendencies, based on the information in the browsing history database; a recommendation strategy decision part which decides a recommendation strategy based on a calculated stability score; and a recommendation part which uses the decided recommendation strategy in order to recommend web pages to the user.

The Strength of Weak Cooperation: an Attempt to Understand the Meaning of Web 2.0

Abstract: This paper examines some continuities and ruptures in the use of Web 2.0 such as blogs, social media, user-generated content services etc. vis-a-vis earlier web services. We hypothesize that one of the sociological characteristics of Web 2.0 services is that making personal production public creates a new articulation between individualism and solidarity, which reveals the strength of weak cooperation. Web 2.0 services allow individual contributors to experience cooperation ex post. The strength of the weak cooperation arises from the fact that it is not necessary for individuals to have an ex ante cooperative action plan or altruistic intention. They discover cooperative opportunities only by making public their individual production. The paper illustrates this phenomenon by analysing the uses of different services and by looking at the new process of innovation that appears through Barcamp and Coworking spaces.

An Infrastructure-Free Traffic Information System for Vehicular Networks

Abstract: Vehicular networks are the major ingredients of the envisioned Intelligent Transportation Systems (ITS) concept. An important component of ITS which is currently attracting wider research focus is road traffic information processing. This has widespread applications in the context of vehicular networks. The existing centralized approaches for traffic estimation are characterized by longer response times. They are also subject to higher processing requirements and possess high deployment costs. In this paper, we propose a completely distributed and infrastructure-free mechanism for road density estimation. The proposed solution is adaptive and scalable and targets city traffic environments. The approach is based on the distributed exchange and maintenance of traffic information between vehicles traversing the routes. The performance analysis of the proposed mechanism shows the accuracy of the algorithm for different traffic densities. It also gives insights into the promptness of information delivery in the mechanism based on delay analysis at road intersections. This promptness is a necessary condition to various applications requiring reliable decision making based on road traffic awareness.

Divisible E-Cash Systems Can Be Truly Anonymous

Abstract: This paper presents an off-line divisible e-cash scheme where a user can withdraw a divisible coin of monetary value 2Lthat he can parceled and spend anonymously and unlinkably. We present the construction of a security tag that allows to protect the anonymity of honest users and to revoke anonymity only in case of cheat for protocols based on a binary tree structure without using a trusted third party. This is the first divisible e-cash scheme that provides both full unlinkability and anonymity without requiring a trusted third party.

Pervasive Service Composition in the Home Network

Abstract: The home environment becomes ready to host distributed devices dynamically adapting to service availability and reacting to user location and user activity. Sensors, high definition rendering systems, home gateways, wired and wireless controllable equipments are now available. Many protocols enable connectivity and interaction between devices. However, challenges remain: protocol heterogeneity, interface fragmentation and device composition static aspect make self-organization and dynamic reconfiguration hardly achievable. This paper describes attractive scenarios at home which lead to the definition of the pervasive service composition requirements. A software architecture facing the mentioned challenges is proposed over OSGi. It first enables developers to implement distributed plug-n-play applications like a local one. It also delivers a service-oriented middleware allowing spontaneous distributed service composition to occur at runtime.

The effects of neurofeedback training in the cognitive division of the anterior cingulate gyrus

Abstract: This study examines the efficacy of neurofeedback training in the cognitive division of the anterior cingulate gyrus and describes its relationship with cortical regions known to be involved in executive functions. This study was conducted with eight non-clinical students, four male and four female, with a mean age of twenty-two. Learning occurred in the ACcd at significant levels over sessions and in the anterior regions that receive projections from the AC. There appears to be a multidimensional executive circuit that increases in the same frequency in apparent synchrony with the AC and it may be possible to train this sub-cortical region using LNFB.

A chaotic stream cipher and the usage in video protection

Abstract: In this paper, a chaotic stream cipher is constructed and used to encrypt video data selectively. The stream cipher based on a discrete piecewise linear chaotic map satisfies the security requirement of cipher design. The video encryption scheme based on the stream cipher is secure in perception, efficient and format compliant, which is suitable for practical video protection. The video encryption scheme’s performances prove the stream cipher’s practicability.

Spatial Data Multiplexing Over OFDM/OQAM Modulations

Abstract: Multi-carrier modulations (MCM) and especially orthogonal schemes such as orthogonal frequency division multiplexing (OFDM) are currently used in many radio transmission standards. Among these modulations, OFDM/OQAM (also referred as OFDM/Offset QAM) is an interesting alternative to classical OFDM modulation, as it does not require the use of guard interval. This characteristic makes its spectral efficiency optimal. In this paper we investigate the combination of OFDM/OQAM and multiple-input multiple-output (MIMO) over radio channels associated to non iterative and iterative receivers. We focus on spatial data multiplexing (SDM) which is a well known MIMO technique designed to improve the capacity.

Public key cryptography and RFID tags

Abstract: When exploring solutions to some of the formidable security problems facing RFID deployment, researchers are often willing to countenance the use of a strong symmetric primitive such as the AES. At the same time it is often claimed that public key cryptography cannot be deployed on low-cost tags. In this paper we give a detailed analysis of the GPS identification scheme. We show that with regards to all three attributes of space, power, and computation time, the on-tag demands of GPS identification compare favourably to the landmark AES implementation by Feldhofer et al.. Thus, assumed limits to implementing asymmetric cryptography on low-end devices may need to be re-evaluated.

Network-Based Visualization of 3D Landscapes and City Models

Abstract: To improve the visualization of large 3D landscapes and city models in a network environment, the authors use two different types of hierarchical level-of-detail models for terrain and groups of buildings. They also leverage the models to implement progressive streaming in both client-server and peer-to-peer network architectures. Visualizing large photorealistic 3D landscapes and city models has received significant attention over the last 10 years in the computer graphics community. More recently, the availability of broadband Internet access and Web-based visualization techniques is paving the way for large-scale 3D landscapes and city models for a variety of professional and mass-market services. To make such services appealing to a large audience, these 3D models must reach a sufficient level of realism and accuracy. Many solutions are now available to automatically generate 3D models of huge urban environments. Geographic information system (GIS) databases (such as terrain elevation grids, orthophotographs, and a building's footprint and height) provide a good basis for generating such models at affordable cost with minimum human intervention. In the future, the accuracy and realism of 3D city models will be improved thanks to recent progress in data capturing techniques.

Cryptanalysis of GRINDAHL

Abstract: Due to recent breakthroughs in hash functions cryptanalysis, some new hash schemes have been proposed. GRINDAHL is a novel hash function, designed by Knudsen, Rechberger and Thomsen and published at FSE 2007. It has the particularity that it follows the RIJNDAEL design strategy, with an efficiency comparable to SHA-256. This paper provides the first cryptanalytic work on this new scheme. We show that the 256-bit version of GRINDAHL is not collision resistant. With a work effort of approximatively 2112 hash computations, one can generate a collision.

A Telecom Baseband Circuit based on an Asynchronous Network-on-Chip

Abstract: The FAUST chip integrates a baseband processing architecture in which communications between IPs are supported by an asynchronous network-on-chip (NoC). This distributed and modular structure facilitates physical implementation and power management. A 20-node NoC is implemented in 79.5mm2 using 0.13mum 6M CMOS to address 100Mb/s telecom systems