Zigbee over tinyos: Implementation and experimental challenges

The IEEE 802.15.4/Zigbee protocols are a promising technology for Wireless Sensor Networks (WSNs). This paper shares our experience on the implementation and use of these protocols and related technologies in WSNs. We present problems and challenges we have been facing in implementing an IEEE 802.15.4/ZigBee stack for TinyOS in a two-folded perspective: IEEE 802.15.4/ZigBee protocol standards limitations (ambiguities and open issues) and technological limitations (hardware and software). Concerning the former, we address challenges for building scalable and synchronized multi-cluster ZigBee networks, providing a trade-off between timeliness and energy-efficiency. On the latter issue, we highlight implementation problems in terms of hardware, timer handling and operating system limitations. We also report on our experience from experimental test-beds, namely on physical layer aspects such as coexistence problems between IEEE 802.15.4 and 802.11 radio channels

Target localization and autonomous navigation using wireless sensor networks -a pseudogradient algorithm approach

pre-printAutonomous mobile robots (AMRs) operating in unknown environments face twin challenges: 1) localization and 2) efficient directed navigation. This paper describes a two-tiered approach to solving these challenges: 1) by developing novel wireless-sensor-network (WSN)-based localization methods and 2) by using WSN-AMR interaction for navigation. The goal is to have an AMR travel from any point within a WSN-covered region to an identified target location without the aid of global sensing and position information. In this research, the target is reached as follows: 1) by producing a magnitude distribution within the WSN region that has a target-directed pseudogradient (PG) and 2) by having the WSN efficiently navigate the AMRs using the PG. This approach utilizes only the topology of the network and the received signal strength (RSS) among the sensor nodes to create the PG. This research shows that, even in the absence of global positioning information, AMRs can successfully navigate toward a target location using only the RSS in their local neighborhood to compute an optimal path. The utility of the proposed scheme is proved through extensive simulation and hardware experiments

Target Localization and Autonomous Navigation Using Wireless Sensor Networks-A Pseudogradient Algorithm Approach

Abstract-Autonomous mobile robots (AMRs) operating in unknown environments face twin challenges: 1) localization and 2) efficient directed navigation. This paper describes a two-tiered approach to solving these challenges: 1) by developing novel wireless-sensor-network (WSN)-based localization methods and 2) by using WSN-AMR interaction for navigation. The goal is to have an AMR travel from any point within a WSN-covered region to an identified target location without the aid of global sensing and position information. In this research, the target is reached as follows: 1) by producing a magnitude distribution within the WSN region that has a target-directed pseudogradient (PG) and 2) by having the WSN efficiently navigate the AMRs using the PG. This approach utilizes only the topology of the network and the received signal strength (RSS) among the sensor nodes to create the PG. This research shows that, even in the absence of global positioning information, AMRs can successfully navigate toward a target location using only the RSS in their local neighborhood to compute an optimal path. The utility of the proposed scheme is proved through extensive simulation and hardware experiments. Index Terms-Goal-directed navigation, pseudo topological gradient, wireless received signal strength (RSS), wireless-sensornetwork (WSN)-assisted target localization

Evaluación de un método de localización de baja carga computacional para un sistema Ultra-Wideband.

Este trabajo se enfoca especialmente en la evaluación del comportamiento en diferentes situaciones de un método de baja carga computacional para la estimación de la localización de objetos en interiores. Podemos dividirlo en dos partes bien diferenciadas. La primera parte de este trabajo abarca toda la parte teórica. Está compuesta por los tres primeros apartados. La segunda parte es la parte puramente experimental, donde se analizan los resultados obtenidos de los experimentos realizados. En los primeros apartados explicaremos detalladamente la tecnología utilizada, Ultra Wideband (UWB) y por qué es tan indicada para la localización en interiores. Posteriormente, habrá un apartado donde describiremos el entorno de trabajo, dónde y cómo hemos realizado todas las pruebas, así como la descripción de todos los instrumentos utilizados. En una segunda parte, hemos implementado un método de localización en Matlab, el método bounding-box también conocido como Min-Max. Seguidamente, hemos tomado medidas reales en una habitación con varias anclas (transmisores UWB), de manera que se ha podido realizar una evaluación de su comportamiento y comprobar la robustez de este método frente a las medidas sin línea de visión directa (non line of sight,NLOS). Ademas, tambien se mostrarán diversos efectos, como el efecto perímetro, que se producen debido a cómo se distribuyen las anclas. Estos comportamientos y efectos los veremos en situaciones reales.This work focuses especially on the evaluation of the behavior in different situations of a method of low computational load for the estimation of the location of objects in indoor environments. We can divide it into two distinct parts. The first part of this work covers the whole theoretical part. It is composed of the first three sections. The second part is the purely experimental part, where the results obtained from the experiments carried out are analyzed. In the first sections we will explain in detail the technology used, UWB and why it is so indicated for indoor location. Later, there will be a section where we will describe the work environment, where and how we have done all the tests, as well as the description of all the instruments used. In a second part, we have implemented a localization method in Matlab, the bounding-box method, also know as Min-Max. Next, we have taken real measurements in a room with several anchors (UWB transmitters), so that it has been possible to evaluate their behavior and check the robustness of this method against non line of sight (NLOS) measurements. In addition, various effects will also be illustrated, such as the perimeter effect, which occur due to how the anchors are distributed. We will see these behaviors and effects in real situations.Universidad de Sevilla. Grado en Ingeniería de las Tecnologías de Telecomunicació

Evaluación de un método de localización de baja carga computacional para un sistema Ultra-Wideband

Este trabajo se enfoca especialmente en la evaluación del comportamiento en diferentes situaciones de un método de baja carga computacional para la estimación de la localización de objetos en interiores. Podemos dividirlo en dos partes bien diferenciadas. La primera parte de este trabajo abarca toda la parte teórica. Está compuesta por los tres primeros apartados. La segunda parte es la parte puramente experimental, donde se analizan los resultados obtenidos de los experimentos realizados. En los primeros apartados explicaremos detalladamente la tecnología utilizada, Ultra Wideband (UWB) y por qué es tan indicada para la localización en interiores. Posteriormente, habrá un apartado donde describiremos el entorno de trabajo, dónde y cómo hemos realizado todas las pruebas, así como la descripción de todos los instrumentos utilizados. En una segunda parte, hemos implementado un método de localización en Matlab, el método bounding-box también conocido como Min-Max. Seguidamente, hemos tomado medidas reales en una habitación con varias anclas (transmisores UWB), de manera que se ha podido realizar una evaluación de su comportamiento y comprobar la robustez de este método frente a las medidas sin línea de visión directa (non line of sight, NLOS). Ademas, tambien se mostrarán diversos efectos, como el efecto perímetro, que se producen debido a cómo se distribuyen las anclas. Estos comportamientos y efectos los veremos en situaciones reales.Universidad de Sevilla. Grado en Ingeniería de las Tecnologías de Telecomunicació

Engineering a search and rescue application with a wireless sensor network - based localization mechanism

The advent of Wireless Sensor Network (WSN) technologies is paving the way for a panoply of new ubiquitous computing applications, some of them with critical requirements. In the ART-WiSe framework, we are designing a two-tiered communication architecture for supporting real-time and reliable communications in WSNs. Within this context, we have been developing a test-bed application, for testing, validating and demonstrating our theoretical findings - a search&rescue/pursuit-evasion application. Basically, a WSN deployment is used to detect, localize and track a target robot and a station controls a rescuer/pursuer robot until it gets close enough to the target robot. This paper describes how this application was engineered, particularly focusing on the implementation of the localization mechanism

On the use of IEEE 802.15.4/Zigbee for time-sensitive wireless sensor network applications

Mestrado em Engenharia Electrotécnica e de ComputadoresRecent advancements in information and communication technologies are paving the way for new paradigms in embedded computing systems. This, allied with an increasing eagerness for monitoring and controlling everything, everywhere, is pushing forward the design of new Wireless Sensor Network (WSN) infrastructures that will tightly interact with the physical environment, in a ubiquitous and pervasive fashion. Such cyber-physical systems require a rethinking of the usual computing and networking concepts, and given that the computing entities closely interact with their environment, timeliness is of increasing importance. This Thesis addresses the use of standard protocols, particularly IEEE 802.15.4 and ZigBee, combined with commercial technologies as a baseline to enable WSN infrastructures capable of supporting the Quality of Service (QoS) requirements (specially timeliness and system lifetime) that future large-scale networked embedded systems will impose. With this purpose, in this Thesis we start by evaluating the network performance of the IEEE 802.15.4 Slotted CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism for different parameter settings, both through simulation and through an experimental testbed. In order to improve the performance of these networks (e.g. throughput, energyefficiency, message delay) against the hidden-terminal problem, a mechanism to mitigate it was implemented and experimentally validated. The effectiveness of this mechanism was also demonstrated in a real application scenario, featuring a target tracking application. A methodology for modelling cluster-tree WSNs and computing the worst-case endto-end delays, buffering and bandwidth requirements was tested and validated experimentally. This work is of paramount importance to understand the behaviour of WSNs under worst-case conditions and also to make the appropriate network settings. Our experimental work enabled us to identify a number of technological constrains, namely related to hardware/software and to the Open-ZB implementation in TinyOS. In this line, a new implementation effort was triggered to port the Open-ZB IEEE 802.15.4/ZigBee protocol stack to the ERIKA real-time operating system. This implementation was validated experimentally and its behaviour compared with the TinyOS–based implementation.Os últimos avanços nas tecnologias de informação e comunicação (ICTs) estão a abrir caminho para novos paradigmas de sistemas computacionais embebidos. Este facto, aliado à tendência crescente em monitorizar e controlar tudo, em qualquer lugar, está a alimentar o desenvolvimento de novas infra-estruturas de Redes de Sensores Sem Fios (WSNs), que irão interagir intimamente com o mundo físico de uma forma ubíqua. Este género de sistemas ciber-físicos de grande escala, requer uma reflexão sobre os conceitos de redes e de computação tradicionais, e tendo em conta a proximidade que estas entidades partilham com ambiente envolvente, o seu comportamento temporal é de acrescida importância. Esta Tese endereça a utilização de protocolos normalizados, em particular do IEEE 802.15.4 e ZigBee em conjunto com tecnologias comerciais, para desenvolver infraestruturas WSN capazes de responder aos requisitos de Qualidade de Serviço (QoS) (especialmente em termos de comportamento temporal e tempo de vida do sistema), que os futuros sistemas embebidos de grande escala deverão exigir. Com este propósito, nesta Tese começamos por analisar a performance do mecanismo de Slotted CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) do IEEE 802.15.4 para diferentes parâmetros, através de simulação e experimentalmente. De modo a melhorar a performance destas redes (ex. throughput, eficiência energética, atrasos) em cenários que contenham nós escondidos (hidden-nodes), foi implementado e validado experimentalmente um mecanismo para eliminar este problema. A eficácia deste mecanismo foi também demonstrada num cenário aplicacional real. Foi testada e validada uma metodologia para modelizar uma WSN em cluster-tree e calcular os piores atrasos das mensagens, necessidades de buffering e de largura de banda. Este trabalho foi de grande importância para compreender o comportamento deste tipo de redes para condições de utilização limite e para as configurar a priori. O nosso trabalho experimental permitiu identificar uma série de limitações tecnológicas, nomeadamente relacionadas com hardware/software e outras relacionadas com a implementação do Open-ZB em TinyOS. Isto desencadeou a migração da pilha protocolar IEEE 802.15.4/ZigBee Open-ZB para o ERIKA, um sistema operativo de tempo-real. Esta implementação foi validada experimentalmente e o seu comportamento comparado com o da implementação baseada em TinyOS