A comparison of digital transmission techniques under multichannel conditions at 2.4 GHz in the ISM BAND

In order to meet the observation quality criteria of micro-UAVs, and particularly in the context of the « Trophée Micro-Drones », ISAE/SUPAERO is studying technical solutions to transmit a high data rate from a video payload onboard a micro-UAV. The laboratory has to consider the impact of multipath and shadowing effects on the emitted signal. Therefore fading resistant transmission techniques are considered. This techniques paper have to reveal an optimum trade-off between three parameters, namely: the characteristics of the video stream, the complexity of the modulation and coding scheme, and the efficiency of the transmission, in term of BER

Performances of a GNSS receiver for space-based applications

Space Vehicle (SV) life span depends on its station keeping capability. Station keeping is the ability of the vehicle to maintain position and orientation. Due to external perturbations, the trajectory of the SV derives from the ideal orbit. Actual positioning systems for satellites are mainly based on ground equipment, which means heavy infrastructures. Autonomous positioning and navigation systems using Global Navigation Satellite Systems (GNSS) can then represent a great reduction in platform design and operating costs. Studies have been carried out and the first operational systems, based on GPS receivers, become available. But better availability of service could be obtained considering a receiver able to process GPS and Galileo signals. Indeed Galileo system will be compatible with the current and the modernized GPS system in terms of signals representation and navigation data. The greater availability obtained with such a receiver would allow significant increase of the number of point solutions and performance enhancement. For a mid-term perspective Thales Alenia Space finances a PhD to develop the concept of a reconfigurable receiver able to deal with both the GPS system and the future Galileo system. In this context, the aim of this paper is to assess the performances of a receiver designed for Geosynchronous Earth Orbit (GEO) applications. It is shown that high improvements are obtained with a receiver designed to track both GPS and Galileo satellites. The performance assessments have been used to define the specifications of the future satellite GNSS receiver

A particle filtering approach for joint detection/estimation of multipath effects on GPS measurements

Multipath propagation causes major impairments to Global Positioning System (GPS) based navigation. Multipath results in biased GPS measurements, hence inaccurate position estimates. In this work, multipath effects are considered as abrupt changes affecting the navigation system. A multiple model formulation is proposed whereby the changes are represented by a discrete valued process. The detection of the errors induced by multipath is handled by a Rao-Blackwellized particle filter (RBPF). The RBPF estimates the indicator process jointly with the navigation states and multipath biases. The interest of this approach is its ability to integrate a priori constraints about the propagation environment. The detection is improved by using information from near future GPS measurements at the particle filter (PF) sampling step. A computationally modest delayed sampling is developed, which is based on a minimal duration assumption for multipath effects. Finally, the standard PF resampling stage is modified to include an hypothesis test based decision step

Analysis of non ambiguous BOC signal acquisition performance Acquisition

The Binary Offset Carrier planned for future GNSS signal, including several GALILEO Signals as well as GPS M-code, presents a high degree of spectral separation from conventional signals. It also greatly improves positioning accuracy and enhances multipath rejection. However, with such a modulation, the acquisition process is made more complex. Specific techniques must be employed in order to avoid unacceptable errors. This paper assesses the performance of three method allowing to acquire and track BOC signal unambiguously : The Bump-jumping technique, The "BPSK-like" technique and the subcarrier Phase cancellation technique

A rao-blackwellized particle filter for INS/GPS integration

The localization performance of a navigation system can be improved by coupling different types of sensors. This paper focuses on INS-GPS integration. INS and GPS measurements allow to dene a non-linear state space model, which is appropriate to particle ltering. This model being conditionally linear Gaussian, a Rao-Blackwellization procedure can be applied to reduce the variance of the estimates

Screening in Medullary Thyroid Carcinoma

The four-year experience of the French collaborative study on medullary thyroid carcinoma (MTC) has permitted improvement in family screening by a common discussion of data and a network of coordinators throughout France involved in the detection of new cases. Investigations have been directed at improving the discrimination between sporadic and hereditary forms of MTC and between individuals who have or have not inherited the disease within families

Detection of variance changes and mean value jumps in measurement noise for multipath mitigation in urban navigation

This paper studies an urban navigation filter for land vehicles. Typical urban-canyon phenomena as multipath and GPS outages seriously degrade positioning performance. To deal with these scenarios a hybrid navigation system using GPS and dead-reckoning sensors is presented. This navigation system is complemented by a two-step detection procedure that classifies outliers according to their associated source of error. Two different situations will be considered in the presence of multipath. These situations correspond to the presence or absence of line of sight for the different GPS satellites. Therefore, two kinds of errors are potentially “corrupting” the pseudo-ranges, modeled as variance changes or mean value jumps in noise measurements. An original multiple model approach is proposed to detect, identify and correct these errors and provide a final consistent solution

Towards generic satellite payloads: software radio

Satellite payloads are becoming much more complex with the evolution towards multimedia applications. Moreover satellite lifetime increases while standard and services evolve faster, necessitating a hardware platform that can evolves for not developing new systems on each change. The same problem occurs in terrestrial systems like mobile networks and a foreseen solution is the software defined radio technology. In this paper we describe a way of introducing this concept at satellite level to offer to operators the required flexibility in the system. The digital functions enabling this technology, the hardware components implementing the functions and the reconfiguration processes are detailed. We show that elements of the software radio for satellites exist and that this concept is feasible

La modélisation pragmatiste de l'action didactique de l'enseignant comme théorie ancrée.: Analyses de cas relatifs à des séances de sciences s'appuyant sur des démarches d'investigation avec utilisation de documents vidéo.

International audienceLes didacticiens ont investi le domaine de l'enseignement par démarche d'investigation en sciences selon différentes options de recherche, liées aux objectifs qu'ils se fixent : propositions de séances, ingénieries didactiques en co-élaboration, analyses de pratiques (voir par exemple, Calmettes, 2012a ; Grangeat, 2013). À l'issue de ces études, un certain nombre de constats peuvent être posés :-Il existe une certaine variabilité dans les modalités de préparation (Bécu-Robinaut, 2007) et dans les mises en oeuvre des séances (Calmettes, 2009 ; Grangeat, 2013).-Lorsque les chercheurs analysent les séances, d'un point de vue externe, ils repèrent des écarts entre les perspectives apparamment ouvertes par les démarches d'investigation en termes épistémologiques et constructivistes, les discours généraux des enseignants à propos de ces démarches et ce qu'ils font dans les classes (Calmettes & al., 2008).Pour tenter d'avancer dans la compréhension de l'action didactique de l'enseignant en classe ordinaire, nous avons proposé récemment une nouvelle approche théorique didactique en nous appuyant notamment sur des idées et des principes issus de la philosophie et de la sociologie : la modélisation pragmatiste de l'action didactique de l'enseignant (Calmettes, 2010). L'objectif de cette communication est, d'abord de présenter le cadre général de construction de cette approche, ensuite de décrire rapidement les concepts qui y sont développés, enfin d'illustrer le travail visant à la faire évoluer, à partir d'études monographiques, dans de nouveaux contextes