Localization in Wireless Sensor Networks

International audienceWith the proliferation of Wireless Sensor Networks (WSN) applications, knowing the node current location have become a crucial requirement. Location awareness enables various applications from object tracking to event monitoring, and also supports core network services such as: routing, topology control, coverage, boundary detection and clustering. Therefore, WSN localization have become an important area that attracted significant research interest. In the most common case, position related parameters are first extracted from the received measurements, and then used in a second step for estimating the position of the tracked node by means of a specific algorithm. From this perspective, this chapter is intended to provide an overview of the major localization techniques, in order to provide the reader with the necessary inputs to quickly understand the state-of-the-art and/or apply these techniques to localization problems such as robot networks. We first review the most common measurement techniques, and study their theoretical accuracy limits in terms of Cramer-Rao lower bounds. Secondly, we classify the main localization algorithms, taking those measurements as input in order to provide an estimated position of the tracked node(s)

Analysis and evaluation of Wi-Fi indoor positioning systems using smartphones

This paper attempts to analyze the main algorithms used in Machine Learning applied to the indoor location. New technologies are facing new challenges. Satellite positioning has become a typical application of mobile phones, but stops working satisfactorily in enclosed spaces. Currently there is a problem in positioning which is unresolved. This circumstance motivates the research of new methods. After the introduction, the first chapter presents current methods of positioning and the problem of positioning indoors. This part of the work shows globally the current state of the art. It mentions a taxonomy that helps classify the different types of indoor positioning and a selection of current commercial solutions. The second chapter is more focused on the algorithms that will be analyzed. It explains how the most widely used of Machine Learning algorithms work. The aim of this section is to present mathematical algorithms theoretically. These algorithms were not designed for indoor location but can be used for countless solutions. In the third chapter, we learn gives tools work: Weka and Python. the results obtained after thousands of executions with different algorithms and parameters showing main problems of Machine Learning shown. In the fourth chapter the results are collected and the conclusions drawn are shown

Combined use of GPR and Other NDTs for road pavement assessment: an overview

Roads are the main transportation system in any country and, therefore, must be maintained in good physical condition to provide a safe and seamless flow to transport people and goods. However, road pavements are subjected to various defects because of construction errors, aging, environmental conditions, changing traffic load, and poor maintenance. Regular inspections are therefore recommended to ensure serviceability and minimize maintenance costs. Ground-penetrating radar (GPR) is a non-destructive testing (NDT) technique widely used to inspect the subsurface condition of road pavements. Furthermore, the integral use of NDTs has received more attention in recent years since it provides a more comprehensive and reliable assessment of the road network. Accordingly, GPR has been integrated with complementary NDTs to extend its capabilities and to detect potential pavement surface and subsurface distresses and features. In this paper, the non-destructive methods commonly combined with GPR to monitor both flexible and rigid pavements are briefly described. In addition, published work combining GPR with other NDT methods is reviewed, emphasizing the main findings and limitations of the most practical combination methods. Further, challenges, trends, and future perspectives of the reviewed combination works are highlighted, including the use of intelligent data analysis.Xunta de Galicia | Ref. ED431F 2021/08Ministerio de Ciencia e Innovación | Ref. RYC2019–026604-

Predictors of mathematics attainment in hearing impaired children.

Deaf children lag behind their hearing peers in mathematical attainment. The reasons for this delay\ud remain unclear. Two methods were used to identify the causes for this underachievement: a\ud longitudinal investigation of predictors of mathematical attainment, and comparison with hearing\ud children. In order for a cause of delay to be identified, both investigative strategies must produce\ud positive results. The deaf children must lag behind the hearing children on the measures and the\ud same measures must predict deaf children's mathematics attainment.\ud The comparative study: The participants were: a) 42 hearing impaired (HI) children age range from\ud 7;2 years to 9;1 years attending units and special schools located on eight different sites around\ud London; b) 73 hearing children aged from 7;2 years to 8;11 years, classmates of some HI children\ud attending a unit based in a mainstream school. A standardised maths test, a measure of their\ud understanding of additive composition (the Shop Task), a memory scan task and tasks assessing\ud understanding of time concepts were administered to all the children. The last two assessments were\ud developed for the study. The performance by the HI children on standardised assessments was also\ud compared to norms standardised on hearing populations.\ud The deaf obtained significantly lower scores on nearly all of the tasks. In the maths test the\ud mean standardised score for the hearing children was 92.68 and for the deaf children was 78.31.\ud There were also significant differences on the memory scan task — the accuracy rates were lower,\ud memory capacity sizes were smaller and the number processing speed was slower for the deaf\ud children. On the time concept tasks the hearing children obtained significantly more correct\ud responses on the tasks assessing change, ability to infer and order events.\ud When the HI children's performance was compared to the norms of standardised\ud assessments, a similar picture emerged. The mean Number Age was 1;1 year behind the hearing\ud norms. The mean WISC score obtained was one standard deviation below the published mean. Raw\ud scores obtained on the reading comprehension task were too low to be standardised. In assessments\ud of receptive language, the HI children obtained standardised scores that were 1 standard deviation\ud below the mean. It was concluded that all of these variables could be examined as predictor variables\ud in the longitudinal study.\ud The longitudinal study: The HI children participating in the comparison study were assessed twice\ud again over the academic year. The outcome measures were scores on standardised mathematics\ud assessments. The predictors were demographic and medical background; intelligence, language;\ud understanding of time; memory capacity and number processing speed; numerical skills such as\ud counting and additive composition.\ud The only demographic variable consistently associated with mathematics scores was age.\ud Analyses using fixed order multiple regression explored the relationships between the various\ud cognitive, numerical and linguistic predictors and mathematics attainment. After controlling for age\ud and non-verbal IQ, only three predictors remained significant: the language assessments, Shop Task,\ud the Change and Inference Required time concepts tasks. When controlling for age, non-verbal IQ\ud and language ability, only the Shop Task added a significant amount of variance in the equation.\ud This equation explained 44% of the variance in a concurrent analysis and 66% and 64% of the\ud variance in longitudinal predictions 4 and 7 months later, respectively.\ud Conclusions: The present study confirms that HI children are behind their peers in mathematics\ud achievement. Explanations for this delay were sought by identifying areas where their performance\ud is poorer than that of hearing children and predictive of their own progress in mathematics. Although\ud the HI children achieved lower scores in the majority of the assessments in the comparative study\ud only the language measures and the Shop Task satisfied both criteria and added a significant amount\ud of variance in the regression equations in the predictive study. It is concluded that these may be\ud causally related to HI children's delay in mathematics

New Approach of Indoor and Outdoor Localization Systems

Accurate determination of the mobile position constitutes the basis of many new applications. This book provides a detailed account of wireless systems for positioning, signal processing, radio localization techniques (Time Difference Of Arrival), performances evaluation, and localization applications. The first section is dedicated to Satellite systems for positioning like GPS, GNSS. The second section addresses the localization applications using the wireless sensor networks. Some techniques are introduced for localization systems, especially for indoor positioning, such as Ultra Wide Band (UWB), WIFI. The last section is dedicated to Coupled GPS and other sensors. Some results of simulations, implementation and tests are given to help readers grasp the presented techniques. This is an ideal book for students, PhD students, academics and engineers in the field of Communication, localization & Signal Processing, especially in indoor and outdoor localization domains

3D Positioning system with optical sensors using encoding techniques

Esta tesis doctoral se centra en el desarrollo y la mejora de los Sistemas de Posicionamiento Locales (LPS) en interiores, los cuales se utilizan en entornos no compatibles con señales GNSS (Global Navigation Satellite Systems) para localizar, seguir y guiar a personas, objetos o vehículos. Se han realizado numerosos estudios para llevar a cabo un sistema de posicionamiento en entornos interiores, donde las personas pasan aproximadamente el 80% de su tiempo. Algunas de las técnicas propuestas emplean diversas señales, como acústicas, de radiofrecuencia, mecánicas u ópticas, entre otras. Por su bajo coste, facilidad de integración en el entorno de trabajo y ausencia de riesgos para la salud, la tecnología óptica es una alternativa viable que ha comenzado a expandirse rápidamente. Esta tesis aporta propuestas que permiten establecer las bases para el desarrollo de un LPS óptico basado en técnicas de codificación y sensores QADA. Se han propuesto dos diseños: un LPS orientado a la privacidad, basado en un conjunto de cuatro LEDs transmisores, aunque fácilmente extensible a más emisores, que actúan como balizas en ubicaciones conocidas y un único sensor QADA que actúa como el receptor a posicionar; y un LPS centralizado basado en un conjunto de transmisores móviles y al menos dos receptores QADA colocados en ubicaciones conocidas. Se han estudiado los módulos transmisor y receptor. En concreto, se propone un esquema de codificación para la emisión del transmisor, que proporciona capacidad de acceso múltiple, así como robustez frente a bajas relaciones señal a ruido y condiciones adversas como los efectos de multicamino y cerca-lejos. Además, para mejorar las prestaciones de la propuesta sin aumentar significativamente el tiempo de emisión, se han analizado diferentes secuencias y sus longitudes, como los códigos LS (Loosely Synchronized) o las secuencias pseudoaleatorias (Kasami). Por otro lado, el módulo receptor está compuesto por un sensor QADA, una apertura cuadrada y una etapa de filtrado para reducir las interferencias no deseadas. El sensor QADA y la apertura se han modelado para, en primer lugar, analizar la influencia de la longitud de la apertura en la linealidad de las ecuaciones de estimación del punto imagen y, en segundo lugar, determinar los parámetros intrínsecos que modelan el receptor (longitud, altura, desalineación y descentrado de la apertura respecto al sensor QADA), de forma que se pueda implementar un algoritmo de calibración para mejorar la precisión del sistema propuesto. El LPS tiene como objetivo estimar la posición 3D de un objeto estático o en movimiento. Para ello, se diseñan varios algoritmos basados en técnicas de triangulación con determinación de ángulos de llegada (AoA) y técnicas homograficas que resuelven el problema de la perspectiva de n puntos (PnP) del sistema pin-hole propuesto. Todas las propuestas han sido verificadas mediante simulaciones y pruebas experimentales en una gran variedad de situaciones: utilizando luz visible o infrarroja, secuencias LS o Kasami, diferentes longitudes de apertura, distintas distancias entre transmisores y receptores, diferentes algoritmos de posicionamiento y varias rotaciones del receptor. Finalmente, las pruebas experimentales han demostrado que es posible posicionar con errores de menos de 5 centímetros

Earth resources technology satellite spacecraft system design studies. Volume 2, book 1 - Subsystems studies Final report

Developing structure, payload, communication and data handling subsystems for ERT