Téléchargement de Contenus dans les réseaux véhiculaires

L’évolution des systèmes de communications sans fil a permis d’envisager de très nombreuses applications pour les systèmes de transport intelligents (ITS). Elles peuvent ou non utiliser une infrastructure et iront de la sécurité routière aux applications de confort du conducteur ou aux jeux en réseaux. La mise à jour de cartes constitue de notre point de vue une application représentative dans la mesure où ce n’est pas une application de sécurité en tant que telle, mais qu’en revanche elle peut contribuer à réduire les embouteillages en améliorant l’efficacité dans la prise de décisions des conducteurs. Elle possède des caractéristiques facilement identifiables : volume élevé de données, faible contrainte de délai, possibilité de mise en œuvre par des communications d’infrastructure à véhicule, entre véhicules, et hybrides. L’objectif est que les contenus soient téléchargés intégralement par tous les véhicules en un temps minimal, en utilisant le moins de ressources possible et au moindre coût. Les solutions qui sont apparues comme les plus adaptées ont concerné l’utilisation de solutions 802.11p avec ou sans infrastructure. Dans le cas de solutions avec infrastructure, un certain nombre de points d’accès diffuseront des informations avec des zones de couverture le plus souvent disjointes. Vu les tailles de zone retenues et/ou le débit consacré à ce type d’applications, le passage devant un seul point d’accès ne suffira pas à télécharger de telles cartes. Il s’agit alors de définir des stratégies de diffusion d’information. Une première étude a consisté à comparer une stratégie unicast à du broadcast/multicast. Cette dernière se révèle largement meilleure. Une combinaison de ces principes n’améliore pas les performances du système, car le débit consacré à la transmission unicast ne compense pas le débit non utilisé par le broadcast. Le problème provient des doublons reçus par les véhicules en passant auprès de plusieurs points d’accès consécutifs. Afin d’atténuer le phénomène des doublons, nous avons eu recours au Codage Réseau linéaire pseudo-aléatoire. L’idée est que le point d’accès diffuse des combinaisons linéaires de morceaux de fichiers. Le grand nombre de ces combinaisons linéaires réduit de façon significative ce phénomène. De façon complémentaire, nous avons étudié l’utilisation de communications ad-hoc pour combler les morceaux de fichier manquants, en particulier dans le cas d’absence d’infrastructure. Nous avons vérifié que l’on pouvait atteindre de bons résultats dans ce contexte en fonction de la diversité des morceaux de fichiers appartenant aux véhicules rencontrés. ABSTRACT : The evolution of wireless communications systems have enabled to consider many applications for Intelligent Transportation Systems (ITS). They may or may not use the infrastructure. They will consider from the traffic safety applications up to the driver’s comfort or network games. The map updates are, from our point of view, a representative application but in the other hand it can help to reduce congestion in improving efficiency in decision making. It has well-defined characteristics : high volume of data, low delay constraint, possibility of implementation of infrastructure-to-vehicle communications, between vehicles and hybrids. The objective is that the contents are fully downloaded by all vehicles in minimum time, using fewer resources and lower costs. The solutions that have emerged as the most suitable concerned the use of the technology 802.11p with or without infrastructure. In the case of solutions with infrastructure, a number of access points broadcast information with coverage areas most often disjointed. Given the size of area used and/or flow devoted to this type of applications, the transition to a single access point is not enough to download these maps. It is then to define strategies of information dissemination. A first study was to compare a unicast strategy face to broadcast/multicast strategy. The latter appears largely improved. A combination of these principles does not improve system performance, because the flow devoted to unicast transmission does not compensate for the flow not used by the broadcast. The problem is duplicate chunks received by vehicles passing from several consecutive access points. To mitigate the phenomenon of duplication, we used the linear network coding pseudorandom. The idea is that the access point broadcasts linear combinations of chunks of files. The large number of these linear combinations significantly reduces this phenomenon. In a complementary manner, we investigated the use of ad hoc communications to fill the missing chunks of file, particularly in the absence of infrastructure. We verified that we could achieve good results in this context based on the diversity of chunks of files which are owned by the encountered vehicles

Pseudo Random Network Coding in Infrastructure to Vehicle Environment for Data Download

This paper introduces a new approach for infrastructure based content distribution in a vehicular network. It is built on broadcasting and pseudo random network coding. Its main strength is that, being broadcast based, it does not need any feedback channel and thus uses less data rate. Data is transmitted exploiting network coding, multiple linear combinations of data are sent. A vehicle needs to receive a defined number of independent linear combinations to decode the data. The server will send a larger number of different linear combinations. The unreliability of broadcast is thus neutralized through a useful redundancy rather than through re-transmission. Finally, computation of the linear combination coefficients is done so that the overhead is the same as it would be without network coding. Depending on the infrastructure deployed, this technique can be a content distribution solution per se or the first step in a more general solution, the second step being based on collaborative download. The high diversity in transmissions will then be a key feature for the performance of such an application.Quit

Content download in the Vehicular Networks

L’évolution des systèmes de communications sans fil a permis d’envisager de très nombreuses applications pour les systèmes de transport intelligents (ITS). Elles peuvent ou non utiliser une infrastructure et iront de la sécurité routière aux applications de confort du conducteur ou aux jeux en réseaux. La mise à jour de cartes constitue de notre point de vue une application représentative dans la mesure où ce n’est pas une application de sécurité en tant que telle, mais qu’en revanche elle peut contribuer à réduire les embouteillages en améliorant l’efficacité dans la prise de décisions des conducteurs. Elle possède des caractéristiques facilement identifiables : volume élevé de données, faible contrainte de délai, possibilité de mise en œuvre par des communications d’infrastructure à véhicule, entre véhicules, et hybrides. L’objectif est que les contenus soient téléchargés intégralement par tous les véhicules en un temps minimal, en utilisant le moins de ressources possible et au moindre coût. Les solutions qui sont apparues comme les plus adaptées ont concerné l’utilisation de solutions 802.11p avec ou sans infrastructure. Dans le cas de solutions avec infrastructure, un certain nombre de points d’accès diffuseront des informations avec des zones de couverture le plus souvent disjointes. Vu les tailles de zone retenues et/ou le débit consacré à ce type d’applications, le passage devant un seul point d’accès ne suffira pas à télécharger de telles cartes. Il s’agit alors de définir des stratégies de diffusion d’information. Une première étude a consisté à comparer une stratégie unicast à du broadcast/multicast. Cette dernière se révèle largement meilleure. Une combinaison de ces principes n’améliore pas les performances du système, car le débit consacré à la transmission unicast ne compense pas le débit non utilisé par le broadcast. Le problème provient des doublons reçus par les véhicules en passant auprès de plusieurs points d’accès consécutifs. Afin d’atténuer le phénomène des doublons, nous avons eu recours au Codage Réseau linéaire pseudo-aléatoire. L’idée est que le point d’accès diffuse des combinaisons linéaires de morceaux de fichiers. Le grand nombre de ces combinaisons linéaires réduit de façon significative ce phénomène. De façon complémentaire, nous avons étudié l’utilisation de communications ad-hoc pour combler les morceaux de fichier manquants, en particulier dans le cas d’absence d’infrastructure. Nous avons vérifié que l’on pouvait atteindre de bons résultats dans ce contexte en fonction de la diversité des morceaux de fichiers appartenant aux véhicules rencontrés.The evolution of wireless communications systems have enabled to consider many applications for Intelligent Transportation Systems (ITS). They may or may not use the infrastructure. They will consider from the traffic safety applications up to the driver’s comfort or network games. The map updates are, from our point of view, a representative application but in the other hand it can help to reduce congestion in improving efficiency in decision making. It has well-defined characteristics : high volume of data, low delay constraint, possibility of implementation of infrastructure-to-vehicle communications, between vehicles and hybrids. The objective is that the contents are fully downloaded by all vehicles in minimum time, using fewer resources and lower costs. The solutions that have emerged as the most suitable concerned the use of the technology 802.11p with or without infrastructure. In the case of solutions with infrastructure, a number of access points broadcast information with coverage areas most often disjointed. Given the size of area used and/or flow devoted to this type of applications, the transition to a single access point is not enough to download these maps. It is then to define strategies of information dissemination. A first study was to compare a unicast strategy face to broadcast/multicast strategy. The latter appears largely improved. A combination of these principles does not improve system performance, because the flow devoted to unicast transmission does not compensate for the flow not used by the broadcast. The problem is duplicate chunks received by vehicles passing from several consecutive access points. To mitigate the phenomenon of duplication, we used the linear network coding pseudorandom. The idea is that the access point broadcasts linear combinations of chunks of files. The large number of these linear combinations significantly reduces this phenomenon. In a complementary manner, we investigated the use of ad hoc communications to fill the missing chunks of file, particularly in the absence of infrastructure. We verified that we could achieve good results in this context based on the diversity of chunks of files which are owned by the encountered vehicles

Trajectory tracking of a quadrotor using sliding mode control

This paper presents the design of a sliding mode control (SMC) for trajectory tracking of an unmanned aerial vehicle (UAV), quadrotor. A simplified model of the quadrotor is used for the controller design. The robustness of the controller is verified through simulations, and also through data analysis from the experiments in the 3DR Arducopter platform. The SMC algorithms are implemented in a microcontroller that communicates with a human machine interface (HMI), which monitors the behavior and stability of the state variables. The results show effectiveness of the control technique for maintaining stability in the quadrotor under different operating scenarios

Evaluating reliability of ultrashort heart rate variability parameters in metabolic syndrome subjects

Heart rate variability (HRV) analysis is barely employed in healthcare environments mainly because of the lack of standard values determining the sympathovagal balance and the difficulty to register RR stationary series. Recent studies have proposed the use of shorter HRV series. For this work, we use a public metabolic syndrome subjects database retrieved during oral glucose tolerance test. In order to explore ultra-short HRV measures reliability we employ an autoregressive model using Burg method, such that short RR sequences can be evaluated while maintaining a good frequency resolution. RR, SD, rMSSD, LF, HF, LFn and LF/HF were computed for different RR sequences (10 min, 5 min, 1 min, 30 s, 10 s). To evaluate the reliability we used the intraclass correlation coefficient (ICC). Additionally, we compared the sympathovagal balance parameters (LFn, LF/HF) among the stages (basal and 30 min). Considering 10 min long registers as references, parameters obtained from 5 min long series present ICC values above 0.78 for all cases. One min long registers present ICC values above 0.70 only for temporal parameters in both RR series and rMSSD. By comparing LFn and LF/HF parameters among the basal state and 30 min, we observed a significant increase of the sympathetic tone (p < 0.05). However, these differences are important only for 10 and 5 min series. In general, we observe that temporal parameters exhibit higher reliability than those the spectral ones. Nonetheless, registers duration below one min do not present adequate results for the spectral parameters in this work.Bucaramang

Evaluation of two QRS detection algorithm on ECG stress test database

In this paper, we evaluated two well-known QRS algorithms: Pan & Tompkins (PT) and based wavelet transform (WT) on an ECG stress test database. In the absence of an annotated ECG stress test database, the first stage of this work consisted of the database annotation, using RR-time series obtained from an eight leads stress database (DICARDIA). First, the system proposes to users a lead (reference channel) according to its statistical measures. Then the user realizes a visual inspection aimed at validating or denying the channel proposed by the system. As the series contains few artifacts, the annotation is performed using interval of annotations. Preliminary results realized over 31928 beats provide a sensibility of 99.81% and 98.28% respectively for PT and WT. The procedure developed in this work can be seen as a valuable starting point in semiautomatic annotation of large electrocardiographic databases, as well to evaluate and to improve stress ECG delineations.Arequip

CinC Challenge 2013: Comparing three algorithms to extract fetal ECG

This paper reports a comparison between three fetal ECG (fECG) detectors developed during the CinC 2013 challenge for fECG detection. Algorithm A1 is based on Independent Component Analysis, A2 is based on fECG detection of RS Slope and A3 is based on Expectation-Weighted Estimation of Fiducial Points. The proposed methodology was validated using the annotated database available for the challenge. Each detector was characterized in terms of its performance by using measures of sensitivity, (Se), positive predictive value (P+) and delay time (td). Additionally, the database was contaminated with white noise for two SNR conditions. Decision fusion was tested considering the most common types of combination of detectors. Results show that the decision fusion of A1 and A2 improves fQRS detection, maintaining high Se and P+ even under low SNR conditions without a significant tdincrease.Ecuado

Characterizing artifacts in RR stress test time series

Electrocardiographic stress test records have a lot of artifacts. In this paper we explore a simple method to characterize the amount of artifacts present in unprocessed RR stress test time series. Four time series classes were defined: Very good lead, Good lead, Low quality lead and Useless lead. 65 ECG, 8 lead, records of stress test series were analyzed. Firstly, RR-time series were annotated by two experts. The automatic methodology is based on dividing the RR-time series in non-overlapping windows. Each window is marked as noisy whenever it exceeds an established standard deviation threshold (SDT). Series are classified according to the percentage of windows that exceeds a given value, based upon the first manual annotation. Different SDT were explored. Results show that SDT close to 20% (as a percentage of the mean) provides the best results. The coincidence between annotators classification is 70.77% whereas, the coincidence between the second annotator and the automatic method providing the best matches is larger than 63%. Leads classified as Very good leads and Good leads could be combined to improve automatic heartbeat labeling.Orlando Florid

Semiautomatic validation of RR time series in an ECG stress test database

This paper reports an automatic method for characterizing the quality of the RR-time series in the stress test database known as DICARDIA. The proposed methodology is simple and consists in subdividing the RR time series in a set of windows for estimating the quantity of artifacts based on a threshold value that depends on the standard deviation of RR-time series for each recorded lead. In a first stage, a manual annotation was performed considering four quality classes for the RR-time series (Reference lead, Good Lead, Low Quality Lead and Useless Lead). Automatic annotation was then performed varying the number of windows and threshold value for the standard deviation of the RR-time series. The metric used for evaluating the quality of the annotation was the Matching Ratio. The best results were obtained using a higher number of windows and considering only three classes (Good Lead, Low Quality Lead and Useless). The proposed methodology allows the utilization of the online available DICARDIA Stress Test database for different types of research.Ecuado

Decategorizing demographically stereotyped users in a semantic recommender system

In the domain of Digital Television (DTV) broadcasting technology, the enhancement of signals features over classic analog signal transmission allows increasing the amount of content available for TV viewers. Recommender Systems (RS) arose as a suitable choice to assist users in the overwhelming task of selecting audiovisual content, however, the cold-start problem normally associated to the lack of information in early RS stages, causes that user stereotyping approaches are employed meanwhile the lack of information in user profiles is overcome. This paper presents an experimental approach aimed to determine the best conditions for which users who were categorized within a determined stereotype during the cold-start stage, could migrate to a new state in which they receive personalized recommendations. Experimental results show that the best condition under the selected demographic stereotyping scheme for this transition is directly related to the number of TV programs that a user has rated while making use of the system.Valparais