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International audience ; Under the 2004 Agreement on the Promotion, Provision, and Use of GALILEO and GPS Satellite-Based Navigation Systems and Related Applications, the member states of the European Union and the United States agreed on working together, intensifying thus the cooperation on interoperability and compatibility issues between GALILEO and GPS. Among other topics, one important focus was the E1/L1 frequency band, centred at 1575.42 MHz, where the GALILEO Open Service (OS) signal and the modernized L1 civil (L1C) signal are going to be transmitted along with many other RNSS signals. The opportunity to design new signals in this preeminent radionavigation frequency band has significant importance to future users worldwide. Recent joint efforts by United States and European experts have identified MBOC (multiplexed BOC) [1][2][3][4][5] as a promising joint solution for E1 OS and L1C, along with multiple sets of spreading waveforms that yield this optimized spectrum. The resulting optimized E1 OS and L1C spreading modulations enable receivers to obtain significantly better performance in multipath than with previously considered spreading modulations, along with other potential benefits. The optimized spreading modulation provides considerable flexibility for receiver designers, and simpler receivers that employ only BOC(1,1)-based processing, experience very modest performance degradation, compared to the baseline BOC(1,1) spreading modulation.

special issue of the COMM conference, Romanian Military Technical Academy Publishing House ; International audience ; This paper presents a novel strategy for dam monitoring by repeat-pass SAR interferometry. The proposed approach couples sub band / sub-aperture decomposition prior to the GLRT-LQ detector. This method is tested with high-resolution spaceborne InSAR images provided by the TanDEM-X and the TerraSAR-X satellites.

special issue of the COMM conference, Romanian Military Technical Academy Publishing House ; International audience ; This paper presents a novel strategy for dam monitoring by repeat-pass SAR interferometry. The proposed approach couples sub band / sub-aperture decomposition prior to the GLRT-LQ detector. This method is tested with high-resolution spaceborne InSAR images provided by the TanDEM-X and the TerraSAR-X satellites.

This paper introduces a new paradigm for unsupervised audiovisual document structuring. In this paradigm, a novel Nonnegative Matrix Factorization (NMF) algorithm is applied on histograms of counts (relating to a bag of features representation of the content) to jointly discover latent structuring patterns and their activations in time. Our NMF variant employs the Kullback-Leibler divergence as a cost function and imposes a temporal smoothness constraint to the activations. It is solved for using a majorization-minimization technique. The approach proposed is meant to be generic and is particularly well suited to applications where the structuring patterns may overlap in time. As such, it is evaluated on a person-oriented video structuring task, using a challenging database of political debate videos. Our results outperform reference results obtained by a method using Hidden Markov Models. Further, we show the potential that our general approach has for audio speaker diarization.

International audience ; For obvious reasons of cost, discretion and reliability costs, locating and tracking aerial targets under an electromagnetically completely passive paradigm, relying exclusively on illuminators of opportunity, is very appealing for military but also civilian tasks. Such a passive radar system could exploit signals emitted by existing commercial television or radio stations or even satellite signals, such as the ones belonging to the GPS. This paper focuses on target locating and tracking using a network of passive receivers and/or non-cooperative illuminators, forming a multi-static radar configuration. The central idea is to make use of the bi-static Doppler shift. To make tracking possible, more than one bistatic Doppler shift has to be measured and the information combined. It is the purpose of the paper to describe this kind of technique and to present its main issues and workarounds, using a gradual approach. Conclusions and perspectives are drawn in the end.

International audience ; For obvious reasons of cost, discretion and reliability costs, locating and tracking aerial targets under an electromagnetically completely passive paradigm, relying exclusively on illuminators of opportunity, is very appealing for military but also civilian tasks. Such a passive radar system could exploit signals emitted by existing commercial television or radio stations or even satellite signals, such as the ones belonging to the GPS. This paper focuses on target locating and tracking using a network of passive receivers and/or non-cooperative illuminators, forming a multi-static radar configuration. The central idea is to make use of the bi-static Doppler shift. To make tracking possible, more than one bistatic Doppler shift has to be measured and the information combined. It is the purpose of the paper to describe this kind of technique and to present its main issues and workarounds, using a gradual approach. Conclusions and perspectives are drawn in the end.

International audience ; Because of the limited availability of the spectrum allocated for navigation systems, the numerous navigation signals broadcast by Modernized GPS and Galileo system will have to be combined and employ bandwidth-efficient modulations. Indeed, the GPS modernization scheme entails the addition of the new military signal (M-code) to the established C/A and P(Y) codes at the same carrier frequency. One of the most important questions is how to combine this new signal with the legacy ones at the payload level, while maintaining good performance at reception. This problem also exists for Galileo since: - in the L1 band, the Open Service (OS) signal (two channels) and the Public Regulated Service (PRS) signal must be transmitted on the same carrier. - in the E6 band, the Commercial Service (CS) signal must be transmitted with the PRS signal. The Interplex modulation, a particular phase-shiftedkeyed/ phase modulation (PSK/PM), was chosen to transmit all these signals because it is a constant-envelope modulation, thereby allowing the use of saturated power amplifiers with limited signal distortion ([STF, 2002; Rajan and Irvine, 2005]). The main objective of this paper is to study the Interplex modulation, as it is used for the GPS and Galileo signals. In a first part we will present the Interplex modulation, its general formulation and its application for the multiplexing of three signals. Then, we will be interested in the application of this modulation to the GPS L1 signals and the Galileo L1 signals. We will give the general expression of the GPS L1 Interplex signal and show the modification which must be made on the general expression of the Interplex modulation to apply it to the case of the combination of the C/A and P(Y) codes with the new M-code. With regards to the Galileo signals we will study two different cases. In the first case we will consider that the OS signal is a classical BOC(1,1). In the second case we will make the study, assuming that the OS signal is the new signal called ...

International audience ; Ocean Acoustic Tomography (OAT) uses powerful active emissions of repetitive signals causing problems when acoustic discretion is required as in military operations. In this paper, we propose to develop a new concept of OAT, called Discreet Acoustic Tomography (DAT), which is based on a stealthy acoustic signals emission. An appropriate global procedure to synthesize a signal waveform in accordance with the compromise between interception probability and accuracy in channel parameters estimation, is proposed. Finally, this procedure was applied to a realistic scenario of which objective consists in hiding a synthetic signal in ship noise with the constraint to have an accurate estimation of the channel parameters. Results obtained illustrate the interest and the potential of the proposed method.

International audience ; Because of the limited availability of the spectrum allocated for navigation systems, the numerous navigation signals broadcast by Modernized GPS and Galileo system will have to be combined and employ bandwidth-efficient modulations. Indeed, the GPS modernization scheme entails the addition of the new military signal (M-code) to the established C/A and P(Y) codes at the same carrier frequency. One of the most important questions is how to combine this new signal with the legacy ones at the payload level, while maintaining good performance at reception. This problem also exists for Galileo since: - in the L1 band, the Open Service (OS) signal (two channels) and the Public Regulated Service (PRS) signal must be transmitted on the same carrier. - in the E6 band, the Commercial Service (CS) signal must be transmitted with the PRS signal. The Interplex modulation, a particular phase-shiftedkeyed/ phase modulation (PSK/PM), was chosen to transmit all these signals because it is a constant-envelope modulation, thereby allowing the use of saturated power amplifiers with limited signal distortion ([STF, 2002; Rajan and Irvine, 2005]). The main objective of this paper is to study the Interplex modulation, as it is used for the GPS and Galileo signals. In a first part we will present the Interplex modulation, its general formulation and its application for the multiplexing of three signals. Then, we will be interested in the application of this modulation to the GPS L1 signals and the Galileo L1 signals. We will give the general expression of the GPS L1 Interplex signal and show the modification which must be made on the general expression of the Interplex modulation to apply it to the case of the combination of the C/A and P(Y) codes with the new M-code. With regards to the Galileo signals we will study two different cases. In the first case we will consider that the OS signal is a classical BOC(1,1). In the second case we will make the study, assuming that the OS signal is the new signal called ...

International audience ; Ocean Acoustic Tomography (OAT) uses powerful active emissions of repetitive signals causing problems when acoustic discretion is required as in military operations. In this paper, we propose to develop a new concept of OAT, called Discreet Acoustic Tomography (DAT), which is based on a stealthy acoustic signals emission. An appropriate global procedure to synthesize a signal waveform in accordance with the compromise between interception probability and accuracy in channel parameters estimation, is proposed. Finally, this procedure was applied to a realistic scenario of which objective consists in hiding a synthetic signal in ship noise with the constraint to have an accurate estimation of the channel parameters. Results obtained illustrate the interest and the potential of the proposed method.

International audience ; GALILEO, the major contribution of the European Union to the Global Navigation Satellite System (GNSS), will be both independent and complementary to the current GPS. It is still in its design phase, and while the signals have to be finalized, the main specifications have already been confirmed. The Binary Offset Carrier (BOC) modulation is part of the current GALILEO signal plan. A BOC modulation multiplies a spreading code with a square wave sub-carrier that has a frequency multiple of the code rate. It creates a split spectrum with two main lobes shifted from the center frequency by the frequency of the sub-carrier. This modulated signal induces better tracking in white noise and better inherent multipath mitigation compared to the spreading code alone. However, it also makes acquisition more challenging and tracking potentially ambiguous due to its multiple peak autocorrelation function. As a result, an evaluation of its performance under different conditions and research on advanced tracking techniques are necessary to assess its robustness and advantages before final selection. This paper focuses on a specific BOC signal: the BOC(1,1). Working on a given signal, instead of trying to find a generic solution, offers the possibility to fully exploit this signal's characteristics to find a more relevant way to improve its performance and cancel its bias threat. A new innovative tracking technique dedicated to BOC(n,n) signals has therefore been developed using a synthesized local correlation function. It completely removes the sidepeak threat and allows clean acquisition and tracking of any BOC(n,n) signal while keeping the same sharp correlation main peak. Consequently, it does not need to check if tracking is done on the main peak. It also offers a good resistance to long-delay multipath. The particular case of BOC(1,1) is taken as an example throughout the paper due to the strong probability that it will be used by the L1 GALILEO civil signal. Both acquisition and tracking are ...

International audience ; This paper will show how frequency diversity improves the availability of accurate navigation solution of GNSS receivers, in the case of aeronautical applications for instance. Therefore, frequency diversity is a mean to mitigate jamming and interferences, to consider among others. It is very important for civil aviation to handle a probabilistic theory related to involuntary jamming of GNSS receivers, with and without the use of frequency diversity. As a preliminary hypothesis, we assume that the GNSS link budgets has been equally balanced for each considered band Bi, even if a band is provided with more interferers than an other. In this later case, this would mean that the GNSS power is higher in the band provided with more interferers. This first assumption can be translated in probabilistic terms. The second assumption made is a jamming probability much smaller than 1. These assumptions are used to derive: - The probability to lose the navigation solution of a monosystem dual frequency receiver, like a L1/L5 GPS or GALILEO receiver. - The probability to lose the navigation solution of a monosystem tri-frequency receiver, like a L1/L2/L5 GPS receiver or a GALILEO E5a/E5b/L1 or E5b/E6/L1 receiver. An application is computed, for a jamming probability of 1/10000 during a full flight. In such a case, the probability to loose the dual frequency navigation function is 15000 times lower in the case of a tri-frequency monosystem receiver instead of a dual frequency monosystem receiver, and this makes this event an improbable case. Intermediate conclusions has been drawn : Frequency diversity has an enormous potential as an interference mitigation mean, which can be at least as efficient as beam forming reception GNSS antennas. - To have an efficient ionospheric correction, the availability of two frequencies among a single system is necessary - The use of L1C/A, L2C, and L5 is interesting for a more robust GPS receiver. The L2C channel can be considered as a backup ; L2C is the mitigation mean. - The use of E5a, E5b, and L1BOC(1,1) is also very interesting for an aeronautic GALILEO receiver, since all these 3 bands are ARNS. The E6 Galileo frequency (provided with integrity) could even be a backup to one E5 signal componant if necessary. The capabability to process ionospheric corrections using only E5a and E5b GALILEO signal componants will be discussed, thanks to code/carrier divergence observations. The paper will also show that E5b C/No degradation due to military radar spurious is low and acceptable.

International audience ; GALILEO, the major contribution of the European Union to the Global Navigation Satellite System (GNSS), will be both independent and complementary to the current GPS. It is still in its design phase, and while the signals have to be finalized, the main specifications have already been confirmed. The Binary Offset Carrier (BOC) modulation is part of the current GALILEO signal plan. A BOC modulation multiplies a spreading code with a square wave sub-carrier that has a frequency multiple of the code rate. It creates a split spectrum with two main lobes shifted from the center frequency by the frequency of the sub-carrier. This modulated signal induces better tracking in white noise and better inherent multipath mitigation compared to the spreading code alone. However, it also makes acquisition more challenging and tracking potentially ambiguous due to its multiple peak autocorrelation function. As a result, an evaluation of its performance under different conditions and research on advanced tracking techniques are necessary to assess its robustness and advantages before final selection. This paper focuses on a specific BOC signal: the BOC(1,1). Working on a given signal, instead of trying to find a generic solution, offers the possibility to fully exploit this signal's characteristics to find a more relevant way to improve its performance and cancel its bias threat. A new innovative tracking technique dedicated to BOC(n,n) signals has therefore been developed using a synthesized local correlation function. It completely removes the sidepeak threat and allows clean acquisition and tracking of any BOC(n,n) signal while keeping the same sharp correlation main peak. Consequently, it does not need to check if tracking is done on the main peak. It also offers a good resistance to long-delay multipath. The particular case of BOC(1,1) is taken as an example throughout the paper due to the strong probability that it will be used by the L1 GALILEO civil signal. Both acquisition and tracking are studied and compared with the standard tracking algorithm, first theoretically and then using simulations.

International audience ; Many marine scientific, industrial and military applications may require the deployment of underwater acoustic sensor networks for sensing and monitoring. A grid topology with multihop relaying is useful for wide area coverage as well as long distance data transmission. We investigate network architectures where data originate at one end of the grid, and are forwarded along multiple lines. We are particularly interested in transmission schedules that maximize network throughput by exploiting propagation delay to allow multiple simultaneous transmissions. We show that an optimal schedule is necessarily per-node fair, and derive the upper bound on throughput. Furthermore, we present a low-complexity algorithm to find schedules achieving the upper bound, regardless of the size of the network.

International audience ; Many marine scientific, industrial and military applications may require the deployment of underwater acoustic sensor networks for sensing and monitoring. A grid topology with multihop relaying is useful for wide area coverage as well as long distance data transmission. We investigate network architectures where data originate at one end of the grid, and are forwarded along multiple lines. We are particularly interested in transmission schedules that maximize network throughput by exploiting propagation delay to allow multiple simultaneous transmissions. We show that an optimal schedule is necessarily per-node fair, and derive the upper bound on throughput. Furthermore, we present a low-complexity algorithm to find schedules achieving the upper bound, regardless of the size of the network.