Advanced interferometric techniques for high resolution bathymetry

International audienceCurrent high-resolution side scan and multibeam sonars produce very large data sets. However, conventional interferometry-based bathymetry algorithms underestimate the potential information of such soundings, generally because they use small baselines to avoid phase ambiguity. Moreover, these algorithms limit the triangulation capabilities of multibeam echosounders to the detection of one sample per beam, i.e., the zero-phase instant. In this paper we argue that the correlation between signals plays a very important role in the exploration of a remotely observed scene. In the case of multibeam sonars, capabilities can be improved by using the interferometric signal as a continuous quantity. This allows consideration of many more useful soundings per beam and enriches understanding of the environment. To this end, continuous interferometry detection is compared here, from a statistical perspective, first with conventional interferometry-based algorithms and then with high-resolution methods, such as the Multiple Signal Classification (MUSIC) algorithm. We demonstrate that a well-designed interferometry algorithm based on a coherence error model and an optimal array configuration permits a reduction in the number of beam formings (and therefore the computational cost) and an improvement in target detection (such as ship mooring cables or masts). A possible interferometry processing algorithm based on the complex correlation between received signals is tested on both sidescan sonars and multibeam echosounders and shows promising results for detection of small in-water targets

Détection et suivi de trajets multiples en tomographie acoustique océanique

International audienceDans cet article, nous proposons une nouvelle méthode d'estimation de temps de retard pour les canaux de propagation à trajets multiples. Il s'agit d'une méthode bayésienne qui prend en compte la nature de la loi des amplitudes des trajets et du bruit en sortie du circuit de réception. Cette approche conduit à un critère à optimiser simple qui s'écrit comme la norme L1 d'une fonction affine des amplitudes recherchées. Les bonnes performances de cet algorithme sont mises en évidence par des simulations et le traitement de données réelles de tomographie acoustique océanique

Multiphath time delay detection and estimation for ocean acoustic tomographie : a bayesian approach

International audienceA new method for multipath channel time delay estimation is proposed. The authors present a Bayesian approach which takes into account the attenuations and noise distributions at the output of the receiver. This leads to a simple criterion which can be written as the I 1 norm of an affine function of the desired attenuations. The good behaviour of this algorithm is shown on synthetic and real acoustic oceanic tomographic dat

Energy efficiency performance of decode and forward MIMO relay PLC systems

In this paper, we investigate the energy efficiency performance of Multiple-Input-Multiple-Output (MIMO) relay-Assisted Power Line Communication (PLC) networks. We consider a half-duplex Decode and Forward (DF) relay system and compare its performance for both uniform time allocation and optimized time allocation strategies. Based on realistic MIMO PLC channels, obtained from the European Telecommunications Standards Institute (ETSI) Specialist Task Force (STF) 410 field measurement campaign that was performed in six European countries, we show that depending on the idle power consumption of MIMO PLC modems in the relay network, possible energy saving gain can be obtained by using DF MIMO PLC relays

Estimation techniques and simulation platforms for 77 GHz FMCW ACC radars

This paper presents two radar simulation platforms that have been developed and evaluated. One is based on the Advanced Design System (ADS) and the other on Matlab. Both platforms are modeled using homodyne front-end 77 GHz radar, based on commercially available monolithic microwave integrated circuits (MMIC). Known linear modulation formats such as the frequency modulation continuous wave (FMCW) and three-segment FMCW have been studied, and a new variant, the dual FMCW, is proposed for easier association between beat frequencies, while maintaining an excellent distance estimation of the targets. In the signal processing domain, new algorithms are proposed for the three-segment FMCW and for the dual FMCW. While both of these algorithms present the choice of either using complex or real data, the former allows faster signal processing, whereas the latter enables a simplified front-end architecture. The estimation performance of the modulation formats has been evaluated using the Cramer-Rao and Barankin bounds. It is found that the dual FMCW modulation format is slightly better than the other two formats tested in this work. A threshold effect is found at a signal-to-noise ratio (SNR) of 12 dB which means that, to be able to detect a target, the SNR should be above this value. In real hardware, the SNR detection limit should be set to about at least 15 dB