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1
Cunic, Danny. "Discrimination of motor and sensory processing in human EEG by power and synchronization analysis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0024/MQ50458.pdf.
Testo completo
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Brahimaj, Detjon. "Integrating haptic feedback in smart devices : multimodal interfaces and design guidelines." Electronic Thesis or Diss., Université de Lille (2022-....), 2024. http://www.theses.fr/2024ULILN002.
Testo completoAbstract (sommario):
L'intérêt croissant pour l'intégration de la rétroaction haptique dans les produits commerciaux est directement lié aux progrès de la technologie haptique. Notamment, la prolifération des smartphones et des tablettes a conduit à l'intégration de modalités haptiques pour diverses fonctions.Alors que des recherches approfondies ont exploré l'intégration des modalités sensorielles (visuelle, auditive, tactile) dans le toucher passif, il existe un manque relatif de connaissances en ce qui concerne la bimodalité ou la multimodalité dans le contexte du toucher actif. Les technologies émergentes, telles que l'haptique de surface, offrent des opportunités pour étudier divers aspects liés à l'intégration sensorielle.Ce travail fournit des lignes directrices précieuses pour les développeurs, tirées d'études expérimentales dans le domaine du toucher actif. Notre première investigation se concentre sur la relation temporelle entre les retours audio et tactiles, révélant un seuil critique de 200 ms lors des interactions de glissement sur une surface haptique. De plus, nous identifions un délai audio-tactile acceptable de 109 ms pour les gestes de clic avec des boutons virtuels, soulignant la nécessité de prohiber ou de minimiser le délai haptique à moins de 40 ms. Une étude comparative impliquant des individus voyants et aveugles dévoile un aspect crucial de l'inclusion : le respect des limites de synchronisation audio-tactile de la population voyante, concerne les boutons virtuels, permet la conception inclusive d'interfaces adaptées aux deux populations. De plus, nous explorons l'impact de facteurs tels que la stéréoscopie et la déformation de surface sur la perception de la rugosité des textures, démontrant que leur présence peut altérer la rugosité perçue des textures lisses de plus de 20%.En outre, notre recherche explore le potentiel de l'utilisation de casques vibrants pour la localisation d'objets, révélant une sensibilité de 7° pour la modalité haptique, de 8° pour la rétroaction auditive et de 6° pour la rétroaction audio-tactile. Cela met en évidence non seulement la viabilité de la rétroaction haptique en réalité virtuelle pour la localisation d'objets, mais aussi l'amélioration obtenue en renforçant l'expérience sensorielle avec des stimuli audio-tactiles<br>The growing interest in integrating haptic feedback into commercial products is a direct result of advancements in haptic technology. Notably, the proliferation of smartphones and tablets has led to the integration of haptic modalities for various interfaces.While extensive research has explored the integration of sensory modalities (visual, auditory, tactile) in passive touch, there is a relative dearth of knowledge regarding bimodality or multimodality in the context of active touch. Emerging technologies, like surface haptics, offer opportunities to investigate various aspects related to sensory integration.This work provides valuable guidelines for developers, drawing from experimental studies in the realm of active touch. Our initial investigation focuses on the temporal relationship between audio and tactile feedback, revealing a critical 200 ms threshold during sliding interactions on a haptic surface. Moreover, we identify an acceptable audio-tactile delay of 109 ms for click gestures with virtual buttons, emphasizing the need to prohibit or minimize haptic delay to less than 40 ms. A comparative study involving sighted and blind individuals unveils a crucial aspect of inclusion: adhering to synchronization boundaries of the sighted population, relative to virtual buttons, allows for the inclusive design of interfaces accommodating both populations.Additionally, we explore the impact of factors such as stereoscopy and surface deformation on the perception of texture roughness, demonstrating that their presence can alter the perceived roughness of smooth textures by over 20%.Furthermore, our research explores the potential of using vibration headphones for object localization, revealing a sensitivity of 7° for the haptic modality, 8° for auditory feedback, and 6° for audio-tactile. This highlights not only the viability of haptic feedback in virtual reality for object localization but also the improvement achieved by reinforcing the sensory experience with audio-tactile stimuli
3
Pallarés, Valls Oriol. "Time synchronization in underwater acoustic sensor networks." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/403876.
Testo completoAbstract (sommario):
This thesis deals with the development of a time synchronization algorithm for underwater sensor networks. The ease of deployment and maintenance of wireless networks leaded this research to the use of an acoustic communication sensor network to share a common base time between all nodes.
Acoustic signals are well adapted to the underwater medium but experience very challenging impairments such as Doppler, extensive multi-paths and low transmission speed that can nevertheless be corrected at the reception side.
Several acoustic waveforms can be invoked to transmit digital data through the underwater medium, without loss of generality, in this study is considered Orthogonal Frequency- Division Multiplexing (OFDM) communication scheme to exchange data between wireless underwater nodes containing sensor time references. This communication link will be used among others to carry time stamp message required for network synchronization.
Time synchronization is a critical piece of infrastructure of any distributed system. UWSN make extensive use of synchronized time for many services provided by a distributed network. In UWSN, Global Positioning System (GPS) signals are not available and synchronization systems are mostly based on acoustic communication. Owing to high latency of the underwater acoustic transmission channel with respect to cabled or radio network makes the use of conventional synchronization protocols even more challenging underwater.
Many time synchronization algorithms for underwater wireless sensor networks (UWSN) can be found in literature, such as TSHL, D-SYNC, DA-Sync. but only a few of them take into account all the water channel challenges, such as low available bandwidth, long propagation delays and sensor node mobility.
To solve this problem, in this research a further development of the existing time synchronization protocols found in literature is driven. To perform time synchronization we apply Precision Time Protocol (PTP) std. IEEE 1588, which is capable to synchronize two clocks with a precision below hundreds of nanoseconds in a point to point cabled Ethernet Network, and DA-Sync protocol, which is a bidirectional message exchange based method between a master clock and an slave one, and refines its time synchronization parameters by using medium kinematic models.
In cabled synchronization systems, such as PTP, time stamps are acquired in physical layer (PHY) in order to achieve maximum precision, avoiding indeterministic time like Operating System (OS) time slots or medium access protocols. Analogously, it happens in acoustic communication, time stamps are extracted from a large acquisition window, and the improvement of these time stamps is treated in this thesis.
Contrary to cable networks, the low celerity of wave sound makes underwater acoustic communications system very sensitive to Doppler effect, yielding to non-uniform frequency scaling represented by compression or dilatation of the time axis. This frequency scaling can be induced by two factors: motion (sensor mobility, channel variation, etc...) and clock skew receiver between transmitter and receiver. Actually, in order to address this problem, some systems uses expensive inertial sensors for compensating Doppler scaling due to motion and temperature compensated low drift clocks. So in this thesis is evaluated the Doppler scaling caused by motion and skew in order to correct it.
Finally, several tests in the laboratory, test tank, and at sea are performed in order to check the performance of acoustic communication and time synchronization. Results show a correct behavior of hardware and software, and also validate the performance of the time synchronization applied to acoustic UWSN.<br>La sincronización temporal es una pieza clave de cualquier sistema distribuido. Las redes de sensores submarinas hacen uso de los sistemas de sincronización entre nodos para diversos servicios disponibles en cualquier red distribuida. Cabe mencionar que en las redes submarinas, las señales GPS (Global Positioning System) no están disponibles para la referencia temporal, y los sistemas de sincronización se tienen que basar principalmente en comunicaciones acústicas. Además, debido a la alta latencia de dichas redes, la portabilidad de protocolos de sincronización cableados o terrestres, es prácticamente imposible debido a las grandes diferencias de velocidades de propagación de las ondas electromagnéticas frente a las acústicas en el medio marino. Las señales acústicas se adecúan bien al medio submarino, pero presentan una serie de inconvenientes como el efecto Doppler, largas trayectorias multi-camino, además de una velocidad de transmisión baja, que han de ser corregidos en el equipo receptor. Se ha elegido el uso de "Orhtogonal Frequency-Division Multiplexing" (OFDM) como esquema de comunicaciones para el intercambio de datos entre nodos inalámbricos que tienen las bases temporales de cada uno de sus sensores. Este link de comunicaciones será usado, entre otros, para propagar los marcajes de tiempos entre mensajes necesarios para la sincronización de la red. En la literatura se pueden encontrar varios sistemas de sincronización para redes de sensores submarinas basadas en comunicación acústica como TSHL, D-SYNC, DA-Sync, pero sólo unos pocos tienen en cuenta toda la problemática del medio marino, como el bajo ancho de banda, los largos tiempos de propagación, o la movilidad de los sensores. Para resolver esta problemática de la sincronización temporal se ha empleado como referencia "Precision Time Protocol" (PTP) std. IEEE 1588, el cual es capaz de sincronizar dos relojes en una red cableada punto a punto con una precisión por debajo de los centenares de nanosegundos. Además se han empleado sistemas de mejora de la precisión temporal basados en ecuaciones cinemáticas de los nodos, tal y como se presenta en el estudio DA-Sync. En el protocolo PTP, los marcajes de tiempo se realizan en la capa física con el propósito de lograr la mayor precisión posible, ya que de este modo se evitan incertidumbres debidas a las temporizaciones de los sistemas operativos, o los algoritmos de acceso al medio. Análogamente, en esta tesis se presenta un sistema de marcaje de tiempos que extrae mediante hardware el marcaje temporal del inicio de la adquisición de datos. Difiriendo de las redes cableadas, la baja velocidad de propagación de las ondas acústicas en el medio marino hace que la comunicación sea altamente sensible al efecto Doppler, resultando en escalados frecuenciales no uniformes, que afectan a la base temporal dilatándola o comprimiéndola. Este escalado de frecuencia puede deberse a dos factores: movimiento (movimiento de sensores, variaciones del canal, etc.) o derivas del reloj de un nodo frente a otro nodo. Actualmente, para resolver este problema, algunos sistemas utilizan sistemas inerciales muy costosos para estimar el movimiento del sensor y relojes compensados por temperatura. En esta tesis se ha utilizado la información del canal respecto al escalado Doppler, además de las ecuaciones cinemáticas de primer orden, para estimar la movilidad y la deriva de los relojes. Finalmente, varios tests en laboratorio, tanque de agua, y experimentación en el mar son presentados para verificar el correcto funcionamiento de ambos sistemas de comunicación y sincronización. Los resultados validan el funcionamiento de todos los algoritmos software y del hardware, además de verificar el funcionamiento del sistema de sincronización aplicado a redes de sensores submarinas con comunicación acústica.
4
Yang, Ying. "Time Synchronization in Wireless Sensor Networks：A Survey." Thesis, Mittuniversitetet, Institutionen för informationsteknologi och medier, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-16986.
Testo completoAbstract (sommario):
Wireless sensor networks (WSNs) have been used as an important tool inmany fields of science and industry. Time synchronization is also a criticalissue in wireless sensor networks and its aim is to synchronize the local timefor some or all nodes in the network, if necessary. However, wireless sensornetworks are limited in their accuracy, energy efficiency, scalability, and complexityand some traditional time synchronization algorithms such as NetworkTime Protocol (NTP) and Global Positioning System (GPS) are unsuitable forWSNs. This work surveys and evaluates state-of-art time synchronization protocolsbased on many factors including accuracy, energy efficiency, and complexity,and analyzes the effect that time synchronization has in a wirelesssensor network. IN ADDITION, more attention is paid to several time synchronizationalgorithms and their advantages and disadvantages. Also, the surveyprovides a valuable framework for comparing new and existing synchronizationprotocols. According to the evaluation for the performance of time synchronizationalgorithms, this thesis provides assistance in relation to further improvingthe performance of time synchronization. Finally, future research directionsin relation to time synchronization in wireless sensor networks are alsoproposed.
5
Luo, Bin, and 羅斌. "Distributed clock synchronization for wireless sensor networks." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/198812.
Testo completoAbstract (sommario):
Clock synchronization for Wireless Sensor Networks (WSNs) has attracted lots of attention due to its importance for operations in WSNs. In traditional centralized clock synchronization algorithms, all the local information should be transmitted to a fusion center for processing, and the results need to be forwarded back to each individual sensor, thus resulting in a heavy burden on communication and computation in the network. In addition, it also lacks of adaptability to link failures and dynamic changes in the network topology, which greatly prevents their use in WSNs. Hence, in this thesis, we focus on developing energy-efficient distributed clock synchronization algorithms for WSNs.
Firstly, global clock synchronization problem is investigated with time-varying clock parameters (skew and offset) owing to imperfect oscillator circuits. A distributed Kalman filter is developed for clock parameters tracking. The proposed algorithm only requires each node to exchange limited information with its direct neighbors, thus is energy efficient, scalable with network size, and is robust against changes in network connectivity. A low-complexity distributed algorithm based on Coordinate-Descent with Bootstrap (CD-BS) is also proposed to provide rapid initialization of the tracking algorithm. Simulation results show that the proposed distributed tracking algorithm achieves the long-term accuracy for the clock parameters close to the Bayesian Cramer-Rao Lower Bound.
Secondly, the problem of global clock synchronization for WSNs in the presence of unknown exponential delays is studied. The joint maximum likelihood estimator of clock offsets, clock skews and fixed delays of the network is first formulated as a global linear programming (LP) problem. Based on the Alternating Direction Method of Multipliers (ADMM), we propose a fully-distributed synchronization algorithm that has low communication overhead and computation cost. Simulation results show that the proposed algorithm achieves better accuracy than consensus algorithm and the distributed least squares algorithm, and can always converge to the centralized optimal solution.
Finally, global clock synchronization for WSNs under the exponentially distributed delays is re-visited with the fast convergence min-sum algorithm. The synchronization problem is cast into an optimization problem represented by factor graph, and a closed-form expression of the messages passed between nodes are derived. Simulation results show that this distributed algorithm can approach the centralized LP solution with faster convergence speed compared to ADMM-based algorithm.<br>published_or_final_version<br>Electrical and Electronic Engineering<br>Doctoral<br>Doctor of Philosophy
6
Deconda, Keerthi. "Fault tolerant pulse synchronization." Thesis, [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2331.
Testo completo
7
Johansson, Malin. "Synchronization of Acoustic Sensors in a Wireless Network." Thesis, Linköpings universitet, Datorteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-157765.
Testo completoAbstract (sommario):
Geographically distributed networks of acoustic sensors can be used to identify and localize the origin of acoustic phenomena. One area of use is localization of snipers by detecting the bullet's shock wave and the muzzle blast. At FOI Linköping, this system is planned to be adapted from a wire bounded sensor network into a wireless sensor network (WSN). When changing from wire bounded communication to wireless, the issue of synchronization becomes present. Synchronization can be achieved in multiple ways with different benefits depending of the method of choice. This thesis studies the synchronization method of using the highly accurate clock in Global Navigation Satellite System (GNSS) modules. This synchronization method is developed into an independent time stamping device that can be connected to each sensor in the WSN. This ensure that all sensors are synchronized to Coordinated Universal Time (UTC). The thesis starts with a pre-study where different solutions are investigated and evaluated. After the pre-study, a development stage is begun where the best solution is developed into a model to be easily implemented in the future. The result is a model existing of a microcontroller, a timing module and an ADC with built in filter and amplification.
8
Saravanos, Yanos. "Energy-Aware Time Synchronization in Wireless Sensor Networks." Thesis, University of North Texas, 2006. https://digital.library.unt.edu/ark:/67531/metadc5438/.
Testo completoAbstract (sommario):
I present a time synchronization algorithm for wireless sensor networks that aims to conserve sensor battery power. The proposed method creates a hierarchical tree by flooding the sensor network from a designated source point. It then uses a hybrid algorithm derived from the timing-sync protocol for sensor networks (TSPN) and the reference broadcast synchronization method (RBS) to periodically synchronize sensor clocks by minimizing energy consumption. In multi-hop ad-hoc networks, a depleted sensor will drop information from all other sensors that route data through it, decreasing the physical area being monitored by the network. The proposed method uses several techniques and thresholds to maintain network connectivity. A new root sensor is chosen when the current one's battery power decreases to a designated value. I implement this new synchronization technique using Matlab and show that it can provide significant power savings over both TPSN and RBS.
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Ying, Yeqiu. "Synchronization and data detection in wireless sensor networks." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485187.
Testo completoAbstract (sommario):
Wireless'sensor networks (WSNs) have been envisioned as one of the most 'important emerging technologies that can greatly impact the world. With the recent advancement in both electronics and wireless communication networks, implementing WSNs in practical applications has become feasible and can be expected.in the near future. However, current communications protocols are not suitable for use in WSNs due to the unique characteristics and the system constraints such as low power consumption, and low computational and hardware complexity. '\. In this thesis, we focus on the physical (PRY) layer design issues including . transmission medium selection, and transceiver design. Specifically, we first study a WSN architecture with a centralized topology. Motivated by the factor that if not properly treated, carrier frequency offset (CFO) and multipath channel can cause great degradation of data detection performance in conventional carrier-based radio systems (narrow-band and wide-band systems), we address CFO and channel estimation for multiple slave sensor nodes. Relying on a unique TDMA-like training head pattern, the joint multi-user CFO and channel estimation problem can be easily decoupled. Furthermore, the joint CFO and channel estimation for each slave sensor can also be treated separately without significant performance degradation. Different CFO and channel estimators are derived and compared. Optimal training design, specifically the pilot symbols placement, for burst transmission systems is also investigated, and an equal-preamble-postamble (EPP) placement scheme is shown to be optimal. In the second half of the thesis, the emerging ultra-wideband (UWB) radio technology is investigated in the context of WSNs. We believe that this new radio technology is a strong candidate for WSN applications d?e to its unique advantages. The modulation ~d receiver schemes are stqdied and block-coded modulation and a novel noncoherent receiver are proposed for impulse radio (IR) UWB systems. The critical challenge of timing synchronization for IR-UWB signals is also studied, and a new code-assisted synchronization scheme is proposed. This semi-analog based synchronization scheme enables the usage of both coherent and noncoherent receivers, and can be executed under either blind or data-aided mode. In conclusion, this research work is expected to favorably impact the theory, design and implementation of communication transceivers for practical W8Ns.
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Han, Cheng-Yu. "Clock Synchronization and Localization for Wireless Sensor Network." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS453/document.
Testo completoAbstract (sommario):
Les réseaux de capteurs sans fil (WSN) jouent un rôle important dans des applications telles que la surveillance de l'environnement, le suivi de sources et le suivi médical, ...etc. Dans les WSN, les capteurs ont la capacité d'effectuer l'échantillonnage des données, des calculs distribués et de fusionner des données. Pour effectuer ces tâches complexes, la synchronisation des horloges et la localisation sont fondamentales et essentielles. Les WSN ont été largement étudiés ces dernières années et la littérature scientifique rapporte de nombreux résultats qui les rendent applicables pour de nombreuses applications. Pour d'autres, la recherche doit encore trouver des solutions à certains des défis posés par la limitation énergétique, la dynamicité et la faible puissance de calcul. Dans le but de contribuer à la recherche sur les WSN, cette thèse propose de nouveaux algorithmes pour la synchronisation d'horloge et la localisation. La synchronisation d'horloge est nécessaire afin que les effectuent de manière efficace la fusion de données. En appliquant l'algorithme de synchronisation d'horloge, les capteurs établissent un consensus temporel et travaillent donc au même rythme. Compte tenu de la dynamicité, des faibles capacités de calcul et de la parcimonie des WSN, un nouvel algorithme de synchronisation décentralisée à impulsions couplées est proposé pour améliorer la précision de la synchronisation. L'avantage de ce type d'algorithme est que les capteurs échangent des impulsions au lieu de paquets, de sorte que non seulement la communication est efficace, mais aussi robuste à toute défaillance des capteurs dans le réseau. La localisation de capteurs a été largement étudiée dans la littérature scientifique. Cependant, la qualité et la précision de la localisation peuvent encore être améliore. Cette thèse applique l'algorithme LSCR (Régression de régions corrélées à signes dominants) au problème de localisation. Avec LSCR, on évalue des régions de confiance avec des niveaux de confiance prescrits, qui fournissent non seulement on emplacement mais aussi la confiance en cet emplacement. Dans cette thèse, plusieurs approches de localisation sont implémentées et comparées. Le résultat de la simulation montre que, sous hypothèses modérées, LSCR obtient des résultats compétitifs par rapport à d'autres méthodes<br>Wireless sensor networks (WSNs) play an important role in applications such as environmental monitoring, source tracking, and health care,... In WSN, sensors have the ability to perform data sampling, distributed computing and information fusion. To perform such complex tasks, clock synchronization and localization are two fundamental and essential algorithms. WSNs have been widely studied in the past years, and the scientific literature reports many outcomes that make them applicable for some applications. For some others, research still needs to find solutions to some of the challenges posed by battery limitation, dynamicity, and low computing clock rate. With the aim of contributing to the research on WSN, this thesis proposes new algorithms for both clock synchronization and localization. For clock synchronization, sensors converge their local physical clock to perform data fusion. By applying the clock synchronization algorithm, sensors converge the time difference and therefore work at the same rate. In view of dynamicity, low computing and sparsity of WSN, a new pulse-coupled decentralized synchronization algorithm is proposed to improve the precision of the synchronization. The benefit of this kind of algorithm is that sensors only exchange zero-bit pulse instead of packets, so not only the communication is efficient but also robust to any failure of the sensors in the network. Localization of sensors has been widely studied. However, the quality and the accuracy of the localization still have a large room to improve. This thesis apply Leave-out Sign-dominant Correlated Regions (LSCR) algorithm to localization problem. With LSCR, one evaluates the accurate estimates of confidence regions with prescribed confidence levels, which provide not only the location but also the confidence of the estimation. In this thesis, several localization approaches are implemented and compared. The simulation result shows under mild assumptions, LSCR obtains competitive results compared to other methods
11
Sari, Ilkay. "Joint synchronization of clock phase offset, skew and drift in reference broadcast synchronization (RBS) protocol." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1781.
Testo completo
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Sheriff, Nathirulla. "Time Synchronization In ANT Wireless Low Power Sensor Network." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Data- och elektroteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-15068.
Testo completoAbstract (sommario):
Short range wireless data communication networks that are used for sport and health care are sometimes called Wireless Body Area Networks (WBANs) and they are located more or less on a person. Sole Integrated Gait Sensor (SIGS) is a research project in WBAN, where wireless pressure sensors are placed like soles in the shoes of persons with different kinds of deceases. The sensors can measure the pressure of the foot relative to the shoe i.e. the load of the two legs is measured. This information can be useful e.g. to not over or under load a leg after joint replacement or as a bio feedback system to help e.g. post stroke patients to avoid falling. The SIGS uses the ANT Protocol and radio specification. ANT uses the 2.4 GHz ISM band and TDMA is used to share a single frequency. The scheduling of time slots is adaptive isochronous co-existence i.e. the scheduling is not static and each transmitter sends periodically but checks for interference with other traffic on the radio channel. In this unidirectional system sole sensors are masters (transmitters) and the WBAN server is the slave in ANT sense. The message rate is chosen as 8 Hz which is suitable for low power consumption. Hence in the SIGS system, it is necessary to synchronize the left and the right foot sensors because of low message rate. In our thesis, we found a method and developed a prototype to receive the time synchronized data in WBAN server from ANT wireless sensor nodes in SIGS system. For this thesis work, a hardware prototype design was developed. The USB and USART communication protocols were also implemented in the hardware prototype. The suitable method for time synchronization was implemented on the hardware prototype. The implemented method receives the sensor data, checks for the correct stream of data; add timestamp to the sensor data and transmit the data to the Linux WBAN server. The time slots allocation in the ANT protocol was found. Alternative solution for the time synchronization in ANT protocol was also provided. The whole SIGS system was tested for its full functionality. The experiments and analysis which we performed were successful and the results obtained provided good time synchronization protocol for ANT low power wireless sensor network and for Wireless Bio-feedback system.
13
Leng, Mei, and 冷梅. "New advances in clock synchronization for wireless sensor networks." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45880451.
Testo completo
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Gonzalez, Sara (Sara H. ). "A framework for collecting data : revising sensor synchronization methods." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112589.
Testo completoAbstract (sommario):
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (page 29).<br>Data collection is frequently carried out in research, as well as in industry for purposes ranging from quality control to assessing system limits. However, several complications may arise to hinder optimal data collection and analysis, including synchronization of different data types from a variety of sensors. A benchtop model was designed with the primary goal of understanding human-spacesuit interactions through the collection and analysis of force, pressure, and internal kinematics data. This thesis addresses shortcomings in the setup that led to difficulty in data analysis and synchronization and presents a revised framework for collecting these data. A system was designed such that the start of each trial of data collection can be synced across the three types of sensors: a load cell, a pressure mat, and inertial measurement units.<br>by Sara Gonzalez.<br>S.B.
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Nadas, João Pedro Battistella. "Energy eficiente synchronization for alarm driven wireless sensor networks." Universidade Tecnológica Federal do Paraná, 2016. http://repositorio.utfpr.edu.br/jspui/handle/1/2309.
Testo completoAbstract (sommario):
Muitas aplicações de redes de sensores sem fio exigem que nós, além de monitorar certo fenômeno, devem ser capazes de detectar e comunicar eventos assíncronos (e.g. alarmes), o que implica que eles deverão ouvir o meio em modo ocioso, o que é inerentemente um desperdício de energia. Nesse cenário, sincronização de relógio é crucial para operar com eficiência em ciclos de trabalho e minimizar o consumo de energia. Nesta dissertação, avaliamos o impacto do \textit{trade-off} entre a energia gasta com sincronizações mais frequentes e, em troca reduzir a janela de escuta ociosa necessária para que a confiabilidade desejada da comunicação seja atingida. A frequência ideal de sincronizações é obtida analiticamente e corroborada por resultados numéricos, mostrando que é possível gastar uma pequena fração da energia total com uma rede com sincronização mais precisa quando comparada com a manutenção da precisão do relógio mínima exigida pelo fenômeno que está sendo monitorado, aumentando significativamente a vida útil da rede. Além disso, uma solução fechada para o limite superior a este número ideal é derivada através da aproximação de que a energia gasta para transmitir ser muito menos significativa quando comparada à gasta para receber. Usando este resultado, pudemos prever através de simulações que este número ideal será aumentado pela energia de escuta, o número de vezes que um nó precisa ouvir o meio à espera de alarmes, ao nível de confiança em que o sistema foi concebido para trabalhar, ao intervalo de sincronização e à variância da frequência de oscilação relativa entre os nós. Por outro lado, este número será menor quando o custo energético de sincronização for maior (i.e. Quando a energia de comunicação aumentar).<br>Many applications of wireless sensor networks require that nodes, besides monitoring a given phenomenon, must be able to detect and communicate asynchronous events (e.g. alarms), implying that they have to often listen to the medium in idle mode, which is inherently energy wasteful. In such a scenario time synchronization is crucial to efficiently operate in duty-cycles and minimize energy consumption. In this work we assess the impact of the trade-off between spending energy with more frequent synchronizations and in return saving it by reducing the idle listening window necessary for the desired reliability of the communication. The optimal frequency of time synchronizations is obtained analytically and corroborated by numerical results, showing that several times less overall energy may be spent with a finer synchronization when compared with maintaining the minimum clock precision required by the phenomenon being monitored, greatly extending the life-span of the network.Furthermore, a closed form upper bound to this optimal number is derived by approximating transmit power being of much more significance when compared to receive power. Using this result, we predict and then simulate that this optimal number will be increased by the listening power, the number of times which a node has to listen to the medium idly, the level of confidence at which the system is designed to work, the synchronization interval and the variance of the relative oscillation frequency between synchronizing nodes. On the other hand, this number will be smaller when the energy cost of synchronization is higher (e.g. when active communication energy increases).
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Ageev, Anton. "Time Synchronization and Energy Efficiency in Wireless Sensor Networks." Doctoral thesis, Università degli studi di Trento, 2010. https://hdl.handle.net/11572/367826.
Testo completoAbstract (sommario):
Time synchronization is of primary importance for the operation of wireless sensor networks (WSN): time measurements, coordinated actions and event ordering require common time on WSN nodes. Due to intrinsic energy limitations of wireless networks there is a need for new energy-efficient time synchronization solutions, different from the ones that have been developed for wired networks. In this work we investigated the trade-offs between time synchronization accuracy and energy saving in WSN. On the basis of that study we developed a power-efficient adaptive time synchronization strategy, that achieves a target synchronization accuracy at the expense of a negligible overhead. Also, we studied the energy benefits of periodic time synchronization in WSN employing synchronous wakeup schemes, and developed an algorithm that finds the optimal synchronization period to save energy. The proposed research improves state-of-the-art by exploring new ways to save energy while assuring high flexibility and reliable operation of WSN.
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Ageev, Anton. "Time Synchronization and Energy Efficiency in Wireless Sensor Networks." Doctoral thesis, University of Trento, 2010. http://eprints-phd.biblio.unitn.it/260/1/Ageev_PhD_Thesis.pdf.
Testo completoAbstract (sommario):
Time synchronization is of primary importance for the operation of wireless sensor networks (WSN): time measurements, coordinated actions and event ordering require common time on WSN nodes. Due to intrinsic energy limitations of wireless networks there is a need for new energy-efficient time synchronization solutions, different from the ones that have been developed for wired networks. In this work we investigated the trade-offs between time synchronization accuracy and energy saving in WSN. On the basis of that study we developed a power-efficient adaptive time synchronization strategy, that achieves a target synchronization accuracy at the expense of a negligible overhead. Also, we studied the energy benefits of periodic time synchronization in WSN employing synchronous wakeup schemes, and developed an algorithm that finds the optimal synchronization period to save energy. The proposed research improves state-of-the-art by exploring new ways to save energy while assuring high flexibility and reliable operation of WSN.
18
Hult, Alfred. "Time Synchronization of TDOA Sensors Using a Local Reference Signal." Thesis, Linköpings universitet, Kommunikationssystem, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-166744.
Testo completoAbstract (sommario):
Synchronization of distributed time difference of arrival (TDOA) sensor networks can be performed using reference signals from GPS satellites. This method provides high accuracy, but is vulnerable to jamming, and is not reliable enough to be used in military applications. A solution that does not depend on any signals transmitted from external actors is preferred. One way to achieve this is to use reference signals transmitted from a UAV. A UAV is suitable since only local synchronization for a geographically restricted area is necessary. The local synchronization is achieved by estimating the time-delay between the transmission and reception of a reference signal. The estimated time-delay can be used to detect drifts in the clocks of the TDOA sensors. This thesis analyzes com- mon reference signals, to evaluate which provide high accuracy for time-delay estimation, and what properties of the signals influence the estimation accuracy the most. The simulations show that the time-delay estimation performance can reach the same accuracy as synchronization against GPS for different types of signals. An increased bandwidth is more important than an increased signal length or signal-to-noise ratio to improve the estimation accuracy.
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Noh, Kyoung Lae. "New advances in designing energy efficient time synchronization schemes for wireless sensor networks." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1493.
Testo completo
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Kaya, Zahit Evren. "Time Synchronization In Measurement Networks." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12611585/index.pdf.
Testo completoAbstract (sommario):
AMR (Automatic Measurement Reading) applications usually require measurement data to be collected from separate locations. In order to combine the data retrieved from separate sources into a meaningful result, all sources should share a common time sense. Therefore, it is necessary to implement a synchronization scheme in measurement networks. In this thesis, a synchronization scheme which combines GPS (Global Positioning System) and two high accuracy WSN (Wireless Sensor Network) time synchronization algorithms will be proposed and evaluated. The synchronization accuracy of the proposed method is compared to the accuracy of NTP (Network Time Protocol) by simulation. This research work is fully supported by the Public Research Grant Committee (KAMAG) of TUBiTAK within the scope of National Power Quality Project of Turkey with the project No: 105G129.
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Zennaro, Davide. "Clock Synchronization in Wireless Sensor Networks: Statistical and Algorithmic Analysis." Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3422165.
Testo completoAbstract (sommario):
In the past few years, the impressive growth of applications performing tasks in a distributed fashion has been enabled by the availability of tiny, inexpensive devices which, in turn, has been made possible by the recent micro-electromechanical technology advancements. Sparsely disposing small intelligent appliances throughout a specific area is something that the community has become used to. Low cost and low power sensing devices equipped with telecommunication hardware are attractive for use in an infrastructure-less network in which the absence of a central node stands out, making robustness be one of the strengths of this kind of networks. Environmental monitoring and military surveillance are just a few examples of the number of applications suitable for sensor networks; in fact, home automation and several health services also can be implemented given that a distributed network of sensors exists.
Sensors need to keep track of a common time scale. This is fundamental for prolonging the network lifetime, making channel access schemes work properly, for example, or for allowing precise duty cycling among the nodes. Clock synchronization is also basic if the goal of a running application is to track moving objects in the battlefield or, more generally, to perform distributed processing of the sensed data. Since the local notion of time in a sensor is based on a low quality local oscillator, it turns out that even small changes in the environmental conditions, like temperature and pressure, lead to modification in the oscillation frequency of the quartz crystals, thus producing time discrepancies among different sensor nodes as time goes by.
This thesis tackles the problem of clock synchronization in sensor networks, both from a perspective of clock parameters estimation and from an algorithmic point of view, to pursue the final goal of making nodes agree on a common time scale, all across the network.
In the first part of the thesis, the so-called two-way message exchange between two nodes is thoroughly analyzed. After recalling existing results on clock parameters estimation exploiting data collected via this message exchange process on the wireless channel, an innovative mathematical framework is introduced, which encompasses several common assumptions for the random delays present in the collected data, in a more general treatment. Based on this new framework, a factor graph-based clock offset estimator for wireless sensor networks is proposed and evaluated. Comparison of the variance of the estimation error with classical bounds available in the literature shows that the new estimator has extremely good performance, therefore it can be considered outstanding among Bayesian clock offset estimators.
The focus of the second part of the thesis is on the design of distributed consensus algorithms in wireless sensor networks, especially for observations averaging purposes. In fact, an innovative fast consensus algorithm is proposed and evaluated, based on the alternating direction multipliers method, which is a distributed method used to solve minimization problems in an iterative fashion. The new consensus algorithm is compared with the state-of-the-art of fast consensus, showing an excellent convergence rate and an outstanding noise resilience. The proposed algorithm is then applied to solve a network-wide clock synchronization issue, assuming both clock skew and offset for the nodes in the network, showing a relevant performance improvement with respect to previously proposed consensus-based synchronization schemes.
Finally, the Appendix contains a work whose topic falls out of the main stream of this thesis: in uplink cellular networks, based on the knowledge of channel statistics, surrounding base stations are carefully and iteratively chosen in order to provide the mobile terminal a certain quality of service in terms of the maximum allowed outage probability, with the aim of minimizing the overall backhaul network usage.<br>Negli ultimi anni abbiamo assistito alla continua comparsa di applicazioni distribuite, la cui implementabilita' risulta consentita dalla possibilita' di avere a disposizione sensori piccoli ed economici. I recenti progressi tecnologici nel settore micro-elettronico-meccanico hanno infatti consentito una miniaturizzazione dei nodi sensore. La comunita' scientifica si e' oramai abituata alla possibilita', con una spesa minima, di collocare piccoli dispositivi intelligenti lungo un'area specifica. Sensori economici e a basso consumo, una volta muniti dell'hardware necessario per le telecomunicazioni, risultano ideali per l'utilizzo in reti senza infrastruttura, uno scenario in cui spicca l'assenza di un nodo centrale e la robustezza diviene quindi una proprieta' fondamentale. Monitoraggio ambientale e sorveglianza militare sono solamente un paio di esempi di applicazioni adatte a reti di sensori, cosi' come la domotica e l'ambito sanitario risultano scenari in cui l'uso di una rete distribuita di sensori puo' rivelarsi, in effetti, utile e vantaggiosa.
I sensori necessitano di una base temporale comune. Questo bisogno risulta fondamentale al fine di prolungare il tempo di vita di una rete, ottimizzando schemi di accesso deterministico al mezzo, ad esempio, oppure schedulando i periodi di attivita' dei nodi in maniera precisa. La sincronizzazione risulta fondamentale anche in applicazioni legate alla localizzazione, o piu' genericamente, per permettere l'elaborazione distribuita di dati raccolti dai sensori stessi. Dal momento che la nozione di tempo locale in un sensore e' fornita da un oscillatore di bassa qualita', anche minime perturbazioni delle condizioni ambientali (come temperatura e pressione) si riflettono in modifiche nella frequenza di oscillazione del cristallo di quarzo, producendo discrepanze nel comportamento tra oscillatori in diversi sensori, che diventano non trascurabili man mano che il tempo scorre.
Questa tesi affronta il problema della sincronizzazione di clock in reti di sensori, sia da una prospettiva di stima dei parametri di clock, sia da un punto di vista algoritmico lungo tutta la rete, con l'obiettivo finale di permettere ai nodi interessati di trovare una concordanza su una scala temporale comune.
Nella prima parte di questa tesi viene analizzato il processo di scambio di informazioni tra due nodi chiamato two-way message exchange. Dopo aver richiamato la letteratura esistente sulla stima dei parametri del clock utilizzando questo protocollo di scambio dati attravero il canale wireless, viene introdotto un nuovo framework matematico per permettere un'assunzione piu' generale riguardo i ritardi casuali presenti nei dati raccolti. Basandosi su questo framework, viene proposto e studiato un nuovo stimatore del clock offset basato sulla teoria dei factor graphs. Dal confronto della varianza dell'errore di stima con classici limiti inferiori presenti in letteratura risulta che il nuovo stimatore proposto permette degli ottimi risultati, per cui puo' a pieno titolo essere considerato meritevole di menzione nella teoria della stima Bayesiana applicata al clock offset.
La seconda parte della tesi riguarda invece la progettazione di algoritmi di consensus distribuiti per reti di sensori wireless, in special modo per operazioni di averaging svolte in maniera distribuita. Viene proposto e valutato un nuovo algoritmo di consensus velocizzato basato su alternating direction multipliers method, un metodo distribuito per risolvere problemi di minimizzazione in modo iterativo. Il nuovo algoritmo di consensus viene confrontato con lo stato dell'arte del consensus velocizzato, mostrando un'eccellente velocita' di convergenza e una resistenza al rumore migliore rispetto agli altri algoritmi presenti in letteratura. Lo schema proposto viene poi applicato al problema della sincronizzazione di clock in reti di sensori wireless, assumendo presenza di clock skew e clock offset tra i vari oscillatori della rete. L'algoritmo di sincronizzazione risultante consente un rilevante miglioramento delle prestazioni rispetto a schemi di sincronizzazione basati su consensus proposti in precedenza.
Infine, nell'Appendice viene descritto un lavoro il cui argomento si discosta da quello principale della tesi: in reti cellulari in uplink, in base alla statistica del canale le stazioni base cooperanti vengono selezionate tramite l'utilizzo di tecniche iterative con l'obiettivo di garantire al terminale mobile una certa qualita' del servizio in termini di probabilta' di disservizio massima permessa e allo stesso tempo di minimizzare l'utilizzo della rete di backhaul.
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Loke, Yong. "Sensor synchronization, geolocation and wireless communication in a shipboard opportunistic array." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Mar%5FLoke.pdf.
Testo completo
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Zheng, Jun. "Unified approach to time synchronization and localization in wireless sensor networks." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42841434.
Testo completo
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Gimelli, Gabriele. "Studio e valutazione sperimentale di tecniche di sincronizzazione per reti di sensori 6LoWPAN." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15434/.
Testo completoAbstract (sommario):
I recenti progressi nella tecnologia applicata alla produzione dei system-on-a-chip hanno permesso lo sviluppo di piccoli dispositivi per il rilevamento a basso costo, a bassa potenza e multifunzione, che sono in grado di svolgere attività quali il rilevamento, l'elaborazione dati e la comunicazione.
Una rete di sensori wireless (WSN) è una rete distribuita che consiste, in generale, di un gran numero di nodi di sensori, densamente distribuiti su un'ampia area geografica per tracciare un determinato fenomeno fisico.
Le reti di sensori wireless sono oggigiorno utilizzate in un'ampia gamma di applicazioni come quelle mediche, industriali, militari, ambientali, scientifiche e in reti domestiche.
In tutte queste applicazioni, la sincronizzazione temporale è un componente molto importante di una rete di sensori wireless, come del resto in ogni sistema distribuito.
Questa tesi ha come scopo principale lo studio dei protocolli esistenti che consentono di risolvere il problema della sincronizzazione tra i nodi di una rete wireless, analizzando in particolare le tecniche TPSN e FTSP. Queste tecniche sono poi state implementate all'interno di una rete wireless di sensori 6LoWPAN già esistente, osservandone poi le performance tramite una serie di test effettuati tramite l'utilizzo della rete all'interno di un ambiente reale.
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Bheemidi, Dheeraj Reddy. "A Wrapper-based Approach to Sustained Time Synchronization in Wireless Sensor Networks." Cleveland State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=csu1231440842.
Testo completo
26
Chaudhari, Qasim Mahmood. "Estimation of clock parameters and performance benchmarks for synchronization in wireless sensor networks." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2945.
Testo completo
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Park, Sung C. "A hybrid time synchronization algorithm based on broadcast sequencing for wireless sensor networks." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/43973.
Testo completoAbstract (sommario):
Approved for public release; distribution is unlimited<br>In recent years, time synchronization has emerged as an essential research topic for wireless sensor networks. Numerous wireless network applications require a common reference time for collaborative data fusion and communications. Other time synchronization protocols have been proposed over the years, but none have eliminated the possibility of collisions associated with wireless packet transmissions while maintaining a precise level of synchronization for any given topology. In this thesis, we present a new hybrid time synchronization scheme that provides a high degree of network-wide synchronization and eliminates the possibility of collisions when transmitting timestamp messages. We propose an algorithm that allows a network to determine a broadcast sequence by which nodes transmit and forward messages and then conducts a network-wide synchronization based on received timestamp information. The proposed hybrid time synchronization scheme utilizes two existing protocols, namely relative referenceless receiver/receiver synchronization and ratio-based synchronization protocol, that provide a high degree of precision. We implement our broadcast sequencing algorithm in simulations and demonstrate its effective performance for a series of network topologies. We also present results demonstrating an improvement in network-wide synchronization using our hybrid scheme over other time synchronization protocols.
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Suul, Jon Are. "Control of Grid Integrated Voltage Source Converters under Unbalanced Conditions : Development of an On-line Frequency-adaptive Virtual Flux-based Approach." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16254.
Testo completoAbstract (sommario):
Three-Phase Voltage Source Converters (VSCs) are finding widespread applications in grid integrated power conversion systems. The control systems of such VSCs are in an increasing number of these applications required to operate during voltage disturbances and unbalanced conditions. Control systems designed for grid side voltagesensor- less operation are at the same time becoming attractive due to the continuous drive for cost reduction and increased reliability of VSCs, but are not commonly applied for operation during unbalanced conditions. Methods for voltage-sensor-less grid synchronization and control of VSCs under unbalanced grid voltage conditions will therefore be the main focus of this Thesis. Estimation methods based on the concept of Virtual Flux, considering the integral of the converter voltage in analogy to the flux of an electric machine, are among the simplest and most well known techniques for achieving voltage-sensor-less grid synchronization. Most of the established techniques for Virtual Flux estimation are, however, either sensitive to grid frequency variations or they are not easily adaptable for operation under unbalanced grid voltage conditions. This Thesis addresses both these issues by proposing a simple approach for Virtual Flux estimation by utilizing a frequency-adaptive filter based on a Second Order Generalized Integrator (SOGI). The proposed approach can be used to achieve on-line frequency-adaptive varieties of conventional strategies for Virtual Flux estimation. The main advantage is, however, that the SOGI-based Virtual Flux estimation can be arranged in a structure that achieves inherent symmetrical component sequence separation under unbalanced conditions. The proposed method for Virtual Flux estimation can be used as a general basis for voltage-sensor-less grid synchronization and control during unbalanced conditions. In this Thesis, the estimated Virtual Flux signals are used to develop a flexible strategy for control of active and reactive power flow, formulated as generalized equations for current reference calculation. A simple, but general, implementation is therefore achieved, where the control objective and the power flow characteristics can be selected according to the requirements of any particular application. Thus, the same control structure can be used to achieve for instance balanced sinusoidal currents or elimination of double frequency active power oscillations during unbalanced conditions. In case of voltage sags, current references corresponding to a specified active or reactive power flow might exceed the current capability of the converter. The limits for active and reactive power transfer during unbalanced conditions have therefore been analyzed, and generalized strategies for current reference calculation when operating under current limitations have been derived. The specified objectives for active and reactive power flow characteristics can therefore be maintained during unbalanced grid conditions, while the average active and reactive power flow is limited to keep the current references within safe values. All concepts and techniques proposed in this Thesis have been verified by simulations and laboratory experiments. The SOGI-based method for Virtual Flux estimation and the strategies for active and reactive power control with current limitation can also be easily adapted for a wide range of applications and can be combined with various types of inner loop control structures. Therefore, the proposed approach can potentially be used as a general basis for Virtual Flux-based voltage-sensor-less operation of VSCs under unbalanced grid voltage conditions.
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Cho, Sunghwan. "Cooperative analog and digital (CANDI) time synchronization protocol for large multi-hop networks." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42915.
Testo completoAbstract (sommario):
For large multihop networks, the time synchronization (TS) error accumulates as the hop number increases with conventional methods, such as Timing-sync Protocol for Sensor Networks (TPSN), Reference Broadcast Synchronization (RBS), and Flooding Time Synchronization Protocol (FTSP). In this paper, to reduce the number of hops to cover the large network and exploit the spatial averaging of TS error between clusters, a novel method combining Concurrent Cooperative Transmission (CCT) and Semi-Cooperative Spectrum Fusion (SCSF) is proposed.
This novel method named Cooperative Analog and Digital (CANDI) Time Synchronization protocol consists of two phases: The digital stage and the analog stage. The digital stage uses CCT to broadcast TS packet containing the time information. Cooperating nodes transmit the digitally encoded message in orthogonal channels simultaneously, so the receiver combines the multiple packet to acheive significant SNR advantage.
In the analog stage, the cooperating nodes simultaneously transmit their slightly different individual estimates of the propagation time by using frequency shift modulation. Nodes receiving this signal combat fading and reduce estimation error in one step through the averaging inherent in diversity combining. Simulation results for two-dimension (2-D) networks are given to evaluate the performance of CANDI, and CANDI is compared with TPSN.
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Bruscato, Leandro Tavares. "Proposta de métodos de sincronização de rede de sensores sem fio." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/169790.
Testo completoAbstract (sommario):
como cidades inteligentes e Internet das coisas demonstram que esta tecnologia está evoluindo em larga escala. Consequentemente, diversas aplicações desta tecnologia estão sendo desenvolvidas, muitas delas são altamente dependentes de redes de sensores sem fio, pois fazem a coleta de dados em ambientes inóspitos ou de difícil acesso. Para que estes dados coletados de diversos dispositivos possam ser analisados em conjunto é preciso que as coletas sejam simultâneas ou em intervalos próximos de tempo, o que implica que toda a rede de sensores tenha uma elevada precisão no sincronismo. Ademais, diversos protocolos de comunicação sem fio utilizam o sincronismo para estabelecer o compartilhamento do meio de propagação, tendo assim uma maior eficiência na troca de dados. Ao observar a importância de atender a essa necessidade de sincronização de tempo entre dispositivos usados em redes de sensores sem fio, este trabalho se concentra na proposta, implementação e teste de um serviço de sincronização de tempo para redes de sensores sem fio de baixa potência usando relógios de baixa frequência em tempo real em cada nó. Para implementar este serviço, são propostos três algoritmos baseados em estratégias diferentes para alcançar a sincronização desejada. O primeiro baseia-se em uma métrica simples de correção adaptativa; o segundo baseia-se em um mecanismo de predição; já o terceiro utiliza um mecanismo mais complexo, a correção analítica. Todos os algoritmos tem o mesmo objetivo: fazer com que os relógios dos nós sensores convirjam de forma ágil, em seguida, mantê-los com a maior similaridade possível. O objetivo deste trabalho é apresentar o melhor método que garanta a sincronização, mantendo o baixo consumo de energia em uma rede de sensores. Os resultados experimentais fornecem evidências do sucesso no cumprimento deste objetivo, bem como fornece meios para comparar estas três abordagens considerando os melhores resultados de sincronização e os seus custos em termos de consumo de energia.<br>Environmental monitoring systems are gaining more and more space, concepts such as smart cities and the Internet of things demonstrate that this technology has been developing a lot. Consequently, many applications of this technology are being developed, many of them are dependent on wireless sensor networks, which collect data in inhospitable or difficult-to-access environments. In order to these collected data from several devices to be analyzed together it is necessary that the data collection be simultaneous or at close intervals, which implies that the entire network of sensors has a high precision in the synchronism. In addition, several wireless communication protocols use the synchronism to establish sharing of medium networks, thus having a greater efficiency in the exchange of data. Observing the importance of time synchronization, this work focuses in proposing, implementing and testing time synchronization protocols for low power wireless sensor networks using real time low frequency clocks. To implement this service, three algorithms based on different strategies are proposed to achieve the desired synchronization. The first is based on the simple metric for self-correction; the second is based on a prediction mechanism; while the third uses a more complex mechanism for analytical correction. All the algorithms have the same goal: to make the clock of the sensor nodes converge in an agile way, then to keep them with the greatest possible similarity. The objective of this work is to present the best method to guarantee the synchronization, keeping the low power consumption in a network, sporadically, transmissions. The experimental results provide evidence of success in achieving this goal, as well as providing means to compare these three approaches considering the best synchronization results and their costs in terms of energy consumption. Keywords: Internet of things.
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Tonsing, Christoph Erik. "Energy-efficient MAC protocol for wireless sensor networks." Diss., University of Pretoria, 2008. http://hdl.handle.net/2263/31247.
Testo completoAbstract (sommario):
A Wireless Sensor Network (WSN) is a collection of tiny devices called sensor nodes which are deployed in an area to be monitored. Each node has one or more sensors with which they can measure the characteristics of their surroundings. In a typical WSN, the data gathered by each node is sent wirelessly through the network from one node to the next towards a central base station. Each node typically has a very limited energy supply. Therefore, in order for WSNs to have acceptable lifetimes, energy efficiency is a design goal that is of utmost importance and must be kept in mind at all levels of a WSN system. The main consumer of energy on a node is the wireless transceiver and therefore, the communications that occur between nodes should be carefully controlled so as not to waste energy. The Medium Access Control (MAC) protocol is directly in charge of managing the transceiver of a node. It determines when the transceiver is on/off and synchronizes the data exchanges among neighbouring nodes so as to prevent collisions etc., enabling useful communications to occur. The MAC protocol thus has a big impact on the overall energy efficiency of a node. Many WSN MAC protocols have been proposed in the literature but it was found that most were not optimized for the group of WSNs displaying very low volumes of traffic in the network. In low traffic WSNs, a major problem faced in the communications process is clock drift, which causes nodes to become unsynchronized. The MAC protocol must overcome this and other problems while expending as little energy as possible. Many useful WSN applications show low traffic characteristics and thus a new MAC protocol was developed which is aimed at this category of WSNs. The new protocol, Dynamic Preamble Sampling MAC (DPS-MAC) builds on the family of preamble sampling protocols which were found to be most suitable for low traffic WSNs. In contrast to the most energy efficient existing preamble sampling protocols, DPS-MAC does not cater for the worst case clock drift that can occur between two nodes. Rather, it dynamically learns the actual clock drift experienced between any two nodes and then adjusts its operation accordingly. By simulation it was shown that DPS-MAC requires less protocol overhead during the communication process and thus performs more energy efficiently than its predecessors under various network operating conditions. Furthermore, DPS-MAC is less prone to become overloaded or unstable in conditions of high traffic load and high contention levels respectively. These improvements cause the use of DPS-MAC to lead to longer node and network lifetimes, thus making low traffic WSNs more feasible.<br>Dissertation (MEng)--University of Pretoria, 2008.<br>Electrical, Electronic and Computer Engineering<br>MEng<br>Unrestricted
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Dehmelt, Chris. "Integration of Smart Sensor Buses into Distributed Data Acquisition Systems." International Foundation for Telemetering, 2005. http://hdl.handle.net/10150/604924.
Testo completoAbstract (sommario):
ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada<br>As requirements for the amount of test data continues to increase, instrumentation engineers are under pressure to deploy data acquisition systems that reduce the amount of associated wiring and overall system complexity. Smart sensor buses have been long considered as one approach to address this issue by placing the appropriate signal conditioners close to their respective sensors and providing data back over a common bus. However, the inability to adequately synchronize the operation of the sensor bus to the system master, which is required to correlate analog data measurements, has precluded their use. The ongoing development and deployment of smart sensor buses has reached the phase in which integration into a larger data acquisition system environment must be considered. Smart sensor buses, such as IntelliBus™, have their own unique mode of operation based on a pre-determined sampling schedule, which however, is typically asynchronous to the operation of the (master or controller) data acquisition system and must be accounted for when attempting to synchronize the two systems. IRIG Chapter 4 type methods for inserting data into a format, as exemplified by the handling of MIL-STD-1553 data, could be employed, with the disadvantage of eliminating any knowledge as to when a particular measurement was sampled, unless it is time stamped (similar to the time stamping function that is provided to mark receipt of 1553 command words). This can result in excessive time data as each sensor bus can manage a large number of analog sensor inputs and multiple sensor buses must be accommodated by the data acquisition system. The paper provides an example, using the Boeing developed IntelliBus system and the L3 Communications - Telemetry East NetDAS system, of how correlated data can be acquired from a smart sensor bus as a major subsystem component of a larger integrated data acquisition system. The focus will be specifically on how the IntelliBus schedule can be synchronized to that of the NetDAS formatter. Sample formats will be provided along with a description of how a standalone NetDAS stack and an integrated NetDAS-IntelliBus system would be programmed to create the required output, taking into account the unique sampling characteristics of the sensor bus.
33
García, Pineda Miguel. "A group-based architecture and protocol for wireless sensor networks." Doctoral thesis, Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/27599.
Testo completoAbstract (sommario):
There are many works related to wireless sensor networks (WSNs) where
authors present new protocols with better or enhanced features, others just
compare their performance or present an application, but this work tries to provide
a different perspective. Why don¿t we see the network as a whole and split it into
groups to give better network performance regardless of the routing protocol?
For this reason, in this thesis we demonstrate through simulations that
node¿s grouping feature in WSN improves the network¿s behavior. We propose the
creation of a group-based architecture, where nodes have the same functionality
within the network. Each group has a head node, which defines the area in which
the nodes of such group are located. Each node has a unique node identifier
(nodeID). First group¿s node makes a group identifier (groupID).
New nodes will know their groupID and nodeID of their neighbors. End
nodes are, physically, the nodes that define a group. When there is an event on a
node, this event is sent to all nodes in its group in order to take an appropriate
action. End nodes have connections to other end nodes of neighboring groups and
they will be used to send data to other groups or to receive information from other
groups and to distribute it within their group. Links between end nodes of different
groups are established mainly depending on their position, but if there are multiple
possibilities, neighbor nodes could be selected based on their ability ¿, being ¿ a
choice parameter taking into account several network and nodes parameters. In
order to set group¿s boundaries, we can consider two options, namely: i) limiting
the group¿s diameter of a maximum number of hops, and ii) establishing
boundaries of covered area.
In order to improve the proposed group-based architecture, we add
collaboration between groups. A collaborative group-based network gives better
performance to the group and to the whole system, thereby avoiding unnecessary
message forwarding and additional overheads while saving energy. Grouping
nodes also diminishes the average network delay while allowing scaling the
network considerably. In order to offer an optimized monitoring process, and in
order to offer the best reply in particular environments, group-based collaborative
systems are needed. They will simplify the monitoring needs while offering direct
control.
Finally, we propose a marine application where a variant of this groupbased architecture could be applied and deployed.<br>García Pineda, M. (2013). A group-based architecture and protocol for wireless sensor networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/27599<br>TESIS<br>Premiado
34
Martirosyan, Anahit. "Towards Design of Lightweight Spatio-Temporal Context Algorithms for Wireless Sensor Networks." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19857.
Testo completoAbstract (sommario):
Context represents any knowledge obtained from Wireless Sensor Networks (WSNs) about the object being monitored (such as time and location of the sensed events). Time and location are important constituents of context as the information about the events sensed in WSNs is comprehensive when it includes spatio-temporal knowledge.
In this thesis, we first concentrate on the development of a suite of lightweight algorithms on temporal event ordering and time synchronization as well as localization for WSNs. Then, we propose an energy-efficient clustering routing protocol for WSNs that is used for message delivery in the former algorithm.
The two problems - temporal event ordering and synchronization - are dealt with together as both are concerned with preserving temporal relationships of events in WSNs. The messages needed for synchronization are piggybacked onto the messages exchanged in underlying algorithms. The synchronization algorithm is tailored to the clustered topology in order to reduce the overhead of keeping WSNs synchronized.
The proposed localization algorithm has an objective of lowering the overhead of DV-hop based algorithms by reducing the number of floods in the initial position estimation phase. It also randomizes iterative refinement phase to overcome the synchronicity of DV-hop based algorithms. The position estimates with higher confidences are emphasized to reduce the impact of erroneous estimates on the neighbouring nodes.
The proposed clustering routing protocol is used for message delivery in the proposed temporal algorithm. Nearest neighbour nodes are employed for inter-cluster communication. The algorithm provides Quality of Service by forwarding high priority messages via the paths with the least cost. The algorithm is also extended for multiple Sink scenario.
The suite of algorithms proposed in this thesis provides the necessary tool for providing spatio-temporal context for context-aware WSNs. The algorithms are lightweight as they aim at satisfying WSN's requirements primarily in terms of energy-efficiency, low latency and fault tolerance. This makes them suitable for emergency response applications and ubiquitous computing.
35
Zhang, Boyang. "Real-time software-defined-radio implementation of time-slotted carrier synchronization for distributed beamforming." Worcester, Mass. : Worcester Polytechnic Institute, 2009. http://www.wpi.edu/Pubs/ETD/Available/etd-050509-200154/.
Testo completoAbstract (sommario):
Thesis (M.S.)--Worcester Polytechnic Institute.<br>Keywords: distributed beamforming; carrier synchronization; software-defined-radio; sensor networks; wireless networks; cooperative transmission; virtual antenna arrays. Includes bibliographical references (leaves 168-169).
36
Ostrander, Charles Nicholas. "Phase alignment of asynchronous external clock controllable devices to periodic master control signal using the Periodic Event Synchronization Unit." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/ostrander/OstranderC0509.pdf.
Testo completoAbstract (sommario):
The Periodic Event Synchronization Unit aligns devices without the ability to be triggered by an external source. The primary function of the unit is to align the pattern trigger pulses of two pulse pattern generators which supply four inputs of a multiplexer. The pulse pattern generators lack the ability to start their code according to an external signal. When operating, the designed unit maintains a specific pattern alignment of two binary data streams of 5 gigabits per second as a multiplexer combines them into a data stream of four times the bit rate. In addition to alignment, the unit can introduce offsets of up to 50 nanoseconds to the pattern alignment which corresponds to 250 bits. The unit is designed to allow the alignment of other devices as well, requiring as input the two event signals of the same frequency which need to be aligned. In order to align the devices providing the event pulses, one of the devices must either accept an external clocking source or have the ability to frequency modulate the internal clock. In practice, the test system was able to achieve and maintain the desired signal characteristics from the output of the multiplexer. The unit's robust design is shown by providing alignment of patterns for the full operating range of the pulse pattern generators and allowing a generator pattern to be aligned to a generic event pulse. Use of multiple units allows alignment of additional devices. The development of the Periodic Event Synchronization Unit provided an inexpensive solution to creating very high bit rate signals using preexisting equipment, as no commercial products were found to accomplish the same function.
37
Orhan, Ibrahim. "Performance Monitoring and Control in Wireless Sensor Networks." Licentiate thesis, KTH, Data- och elektroteknik (Stängd 20130701), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-94545.
Testo completoAbstract (sommario):
Wireless personal area networks have emerged as an important communication infrastructure in areas such as at-home healthcare and home automation, independent living and assistive technology, as well as sports and wellness. Wireless personal area networks, including body sensor networks, are becoming more mature and are considered to be a realistic alternative as communication infrastructure for demanding services. However, to transmit data from e.g., an ECG in wireless networks is also a challenge, especially if multiple sensors compete for access. Contention-based networks offer simplicity and utilization advantages, but the drawback is lack of predictable performance. Recipients of data sent in wireless sensor networks need to know whether they can trust the information or not. Performance measurements, monitoring and control is of crucial importance for medical and healthcare applications in wireless sensor networks. This thesis focuses on development, prototype implementation and evaluation of a performance management system with performance and admission control for wireless sensor networks. Furthermore, an implementation of a new method to compensate for clock drift between multiple wireless sensor nodes is also shown. Errors in time synchronization between nodes in Bluetooth networks, resulting in inadequate data fusion, are also analysed.<br><p>QC 20120529</p>
38
Salustiano, Rogerio Esteves 1978. "Núcleo de simulação computacional baseado na sincronização por barreiras com aplicação em redes de sensores sem fio." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260659.
Testo completoAbstract (sommario):
Orientador: Carlos Alberto dos Reis Filho<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação<br>Made available in DSpace on 2018-08-25T00:28:56Z (GMT). No. of bitstreams: 1
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Previous issue date: 2014<br>Resumo: O principal objetivo deste trabalho é a proposta e a implementação de um núcleo de simulação do tipo event-driven baseado em agentes destinado ao estudo e previsão de desempenho de Redes de Sensores Sem Fio. O núcleo de simulação, BaSS ¿ Barrier Synchronization Simulator, foi desenvolvido a partir do modelo básico de sincronização por barreiras, cujas funcionalidades foram ampliadas com a inclusão de temporização e interrupção nos eventos de sincronização, sendo esta a contribuição mais relevante do trabalho. Sendo parte de um projeto com metas mais ambiciosas, em particular a busca de estruturas de Redes de Sensores Sem Fio mais eficientes, contando para isto com o envolvimento de múltiplas expertises, dentre as quais projeto de circuitos integrados, eficiência energética e protocolos de comunicação, o presente trabalho foi motivado pela necessidade de uma ferramenta de simulação suficientemente flexível para acomodar os dispositivos que estariam sendo desenvolvidos e usados nas novas Redes de Sensores Sem Fio. Como resultado, considera-se que os frutos tangíveis deste trabalho são: primeiro, um framework que pode ser utilizado no desenvolvimento de simuladores do tipo event-driven com aplicações diversas e, segundo, um simulador com aplicação específica em Redes de Sensores Sem Fio, que permite a modelagem comportamental dos seus elementos, tais como as propriedades dos sensores, as características de transmissão e recepção e as cargas das baterias. O simulador tem uma interface gráfica que permite a visualização dinâmica da rede e a inclusão de recursos de avaliação e controle da simulação<br>Abstract: The main objective of this work is the proposal and the implementation of an event-driven simulation kernel based on agents for the study and performance prediction of Wireless Sensor Networks The simulation kernel, BaSS - Barrier Synchronization Simulator, was developed based on the barrier synchronization model, whose features were expanded with the inclusion of interruptions and timers in the synchronization of events, which is the most important contribution of this work. As a part of a project with more ambitious purposes, particularly pursuing the development of more efficient wireless sensor networks, counting for this with the involvement of diverse expertises, including design of integrated circuits, energy efficiency and communication protocols, the herein presented work was motivated by the need of a flexible simulation tool to accommodate the devices that would be developed and used in the new wireless sensor networks. As a result, it is understood that the tangible contributions of this work are: first, a framework that can be used in the development of any kind of event-driven simulators and, second, a simulator with a specific application in Wireless Sensor Networks, which allows the behavioural modelling of their elements, such as sensors proprieties, transmission and reception characteristics and batteries charges. The simulator has a graphical interface that allows the dynamic visualization of the network and the use of evaluation resources and controls of the simulation<br>Doutorado<br>Eletrônica, Microeletrônica e Optoeletrônica<br>Doutor em Engenharia Elétrica
39
Karlsson, Leif. "Time-synchronized wireless mesh networks using battery-powered nodes." Thesis, Linnéuniversitetet, Institutionen för datavetenskap och medieteknik (DM), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-75050.
Testo completoAbstract (sommario):
This thesis proposes an implementation of battery-powered, time-synchronized wireless nodes that can be deployed in a wireless network topology. Wireless sensor networks are used in a wide variety of scenarios where emphasis is placed on the wireless nodes’ battery life. The main area of focus in this thesis is to examine how wireless nodes can save battery power by utilizing a deep sleep mode and wake up simultaneously using time synchronization to carry out their data communication. This was achieved by deploying five time-synchronized, battery-powered nodes in a wireless network topology. The difference in battery current draw between continuously running nodes and sleep-enabled nodes were measured, as well as the time duration needed by the nodes to successfully send their payloads and route other nodes’ data. The nodes needed between 1502 ms and 3273 ms on average to carry out their data communication, depending on where they were located in the network topology. Measurements show that sleep-enabled nodes on average draw substantially less current than continuously running nodes during a complete data communication cycle. When sleep-enabled nodes were powered by two AA batteries, an increase in battery life of up to 1800% was observed.
40
Taha, Abu Snaineh Sami. "AUTOMATIC PERFORMANCE LEVEL ASSESSMENT IN MINIMALLY INVASIVE SURGERY USING COORDINATED SENSORS AND COMPOSITE METRICS." UKnowledge, 2013. http://uknowledge.uky.edu/cs_etds/12.
Testo completoAbstract (sommario):
Skills assessment in Minimally Invasive Surgery (MIS) has been a challenge for training centers for a long time. The emerging maturity of camera-based systems has the potential to transform problems into solutions in many different areas, including MIS. The current evaluation techniques for assessing the performance of surgeons and trainees are direct observation, global assessments, and checklists. These techniques are mostly subjective and can, therefore, involve a margin of bias.
The current automated approaches are all implemented using mechanical or electromagnetic sensors, which suffer limitations and influence the surgeon’s motion. Thus, evaluating the skills of the MIS surgeons and trainees objectively has become an increasing concern. In this work, we integrate and coordinate multiple camera sensors to assess the performance of MIS trainees and surgeons.
This study aims at developing an objective data-driven assessment that takes advantage of multiple coordinated sensors. The technical framework for the study is a synchronized network of sensors that captures large sets of measures from the training environment. The measures are then, processed to produce a reliable set of individual and composed metrics, coordinated in time, that suggest patterns of skill development. The sensors are non-invasive, real-time, and coordinated over many cues such as, eye movement, external shots of body and instruments, and internal shots of the operative field. The platform is validated by a case study of 17 subjects and 70 sessions. The results show that the platform output is highly accurate and reliable in detecting patterns of skills development and predicting the skill level of the trainees.
41
Yang, Jue. "Design and Implementation of Large-Scale Wireless Sensor Networks for Environmental Monitoring Applications." Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc28493/.
Testo completoAbstract (sommario):
Environmental monitoring represents a major application domain for wireless sensor networks (WSN). However, despite significant advances in recent years, there are still many challenging issues to be addressed to exploit the full potential of the emerging WSN technology. In this dissertation, we introduce the design and implementation of low-power wireless sensor networks for long-term, autonomous, and near-real-time environmental monitoring applications. We have developed an out-of-box solution consisting of a suite of software, protocols and algorithms to provide reliable data collection with extremely low power consumption. Two wireless sensor networks based on the proposed solution have been deployed in remote field stations to monitor soil moisture along with other environmental parameters. As parts of the ever-growing environmental monitoring cyberinfrastructure, these networks have been integrated into the Texas Environmental Observatory system for long-term operation. Environmental measurement and network performance results are presented to demonstrate the capability, reliability and energy-efficiency of the network.
42
Lopes, Sérgio Ivan Fernandes. "In search of reliable centimeter-level indoor positioning: a smartphone-based approach." Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14100.
Testo completoAbstract (sommario):
Doutoramento em Engenharia Electrotécnica<br>This thesis describes the design and implementation of a reliable
centimeter-level indoor positioning system fully compatible with a conventional
smartphone. The proposed system takes advantage of the
smartphone audio I/O and processing capabilities to perform acoustic
ranging in the audio band using non-invasive audio signals and it has
been developed having in mind applications that require high accuracy,
such as augmented reality, virtual reality, gaming and audio guides. The
system works in a distributed operation mode, i.e. each smartphone is
able to obtain its own position using only acoustic signals. To support
the positioning system, a Wireless Sensor Network (WSN) of synchronized
acoustic beacons is used. To keep the infrastructure in sync we
have developed an Automatic Time Synchronization and Syntonization
(ATSS) protocol with a standard deviation of the sync offset error below
1.25 μs. Using an improved Time Difference of Arrival (TDoA) estimation
approach (which takes advantage of the beacon signals’ periodicity)
and by performing Non-Line-of-Sight (NLoS) mitigation, we were
able to obtain very stable and accurate position estimates with an absolute
mean error of less than 10 cm in 95% of the cases and a mean
standard deviation of 2.2 cm for a position refresh period of 350 ms.<br>Esta tese descreve o projeto e a implementação de um sistema de
localização para ambientes interiores totalmente compatível com um
smartphone convencional. O sistema proposto explora a capacidade
de aquisição de sinais áudio e de processamento do smartphone para
medir distâncias utilizando sinais acústicos na banda do audível; foram
utilizados sinais áudio não-invasivos, i.e. com reduzido impacto perceptual
em humanos. No desenvolvimento deste sistema foram consideradas
aplicações que exigem elevada exatidão, na ordem dos centímetros,
tais como realidade aumentada, realidade virtual, jogos ou
guias virtuais. Utilizou-se uma infraestrutura de faróis de baixo custo
suportada por uma rede de sensores sem fios (RSSF). Para manter
a infraestrutura síncrona, foi desenvolvido um protocolo de sincronização
e sintonização automática, (Automatic Time Synchronization and
Syntonization - ATSS) que garante um desvio padrão do erro de offset
abaixo de 1.25 μs. Cada smartphone efectua medidas MT-TDoA
que posteriormente são utilizadas pelo algoritmo de localização hiperbólica.
As estimativas de posição resultantes são estáveis e precisas,
com um erro médio absoluto menor do que 10 cm em 95% dos casos
e um desvio padrão médio de 2.2 cm, para um período de atualização
de posição de 350 ms.
43
Zhang, Xiaohu. "VHF & UHF energy harvesting radio system physical and MAC layer considerations." Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1435.
Testo completo
44
Cridland, Doug, and Chris Dehmelt. "LONG TERM VEHICLE HEALTH MONITORING." International Foundation for Telemetering, 2007. http://hdl.handle.net/10150/604406.
Testo completoAbstract (sommario):
ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada<br>While any vehicle that is typically part of a flight test campaign is heavily instrumented to validate its performance, long term vehicle health monitoring is performed by a significantly reduced number of sensors due to a number of issues including cost, weight and maintainability. The development and deployment of smart sensor buses has reached a time in which they can be integrated into a larger data acquisition system environment. The benefits of these types of buses include a significant reduction in the amount of wiring and overall system complexity by placing the appropriate signal conditioners close to their respective sensors and providing data back over a common bus, that also provides a single power source. The use of a smart-sensor data collection bus, such as IntelliBus™1 or IEEE-1451, along with the continued miniaturization of signal conditioning devices, leads to the interesting possibility of permanently embedding data collection capabilities within a vehicle after the initial flight test effort has completed, providing long-term health-monitoring and diagnostic functionality that is not available today. This paper will discuss the system considerations and the benefits of a smart sensor based system and how pieces can be transitioned from flight qualification to long-term vehicle health monitoring in production vehicles.
45
Meghji, Mahir Lumumba. "On a Joint Physical Layer and Medium Access Control Sublayer Design for Efficient Wireless Sensor Networks and Applications." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2013. https://ro.ecu.edu.au/theses/590.
Testo completoAbstract (sommario):
Wireless sensor networks (WSNs) are distributed networks comprising small sensing devices equipped with a processor, memory, power source, and often with the capability for short range wireless communication. These networks are used in various applications, and have created interest in WSN research and commercial uses, including industrial, scientific, household, military, medical and environmental domains. These initiatives have also been stimulated by the finalisation of the IEEE 802.15.4 standard, which defines the medium access control (MAC) and physical layer (PHY) for low-rate wireless personal area networks (LR-WPAN).
Future applications may require large WSNs consisting of huge numbers of inexpensive wireless sensor nodes with limited resources (energy, bandwidth), operating in harsh environmental conditions. WSNs must perform reliably despite novel resource constraints including limited bandwidth, channel errors, and nodes that have limited operating energy. Improving resource utilisation and quality-of-service (QoS), in terms of reliable connectivity and energy efficiency, are major challenges in WSNs. Hence, the development of new WSN applications with severe resource constraints will require innovative solutions to overcome the above issues as well as improving the robustness of network components, and developing sustainable and cost effective implementation models.
The main purpose of this research is to investigate methods for improving the performance of WSNs to maintain reliable network connectivity, scalability and energy efficiency. The study focuses on the IEEE 802.15.4 MAC/PHY layers and the carrier sense multiple access with collision avoidance (CSMA/CA) based networks. First, transmission power control (TPC) is investigated in multi and single-hop WSNs using typical hardware platform parameters via simulation and numerical analysis. A novel approach to testing TPC at the physical layer is developed, and results show that contrary to what has been reported from previous studies, in multi-hop networks TPC does not save energy.
Next, the network initialization/self-configuration phase is addressed through investigation of the 802.15.4 MAC beacon interval setting and the number of associating nodes, in terms of association delay with the coordinator. The results raise doubt whether that the association energy consumption will outweigh the benefit of duty cycle power management for larger beacon intervals as the number of associating nodes increases.
The third main contribution of this thesis is a new cross layer (PHY-MAC) design to improve network energy efficiency, reliability and scalability by minimising packet collisions due to hidden nodes. This is undertaken in response to findings in this thesis on the IEEE 802.15.4 MAC performance in the presence of hidden nodes. Specifically, simulation results show that it is the random backoff exponent that is of paramount importance for resolving collisions and not the number of times the channel is sensed before transmitting. However, the random backoff is ineffective in the presence of hidden nodes. The proposed design uses a new algorithm to increase the sensing coverage area, and therefore greatly reduces the chance of packet collisions due to hidden nodes. Moreover, the design uses a new dynamic transmission power control (TPC) to further reduce energy consumption and interference. The above proposed changes can smoothly coexist with the legacy 802.15.4 CSMA/CA.
Finally, an improved two dimensional discrete time Markov chain model is proposed to capture the performance of the slotted 802.15.4 CSMA/CA. This model rectifies minor issues apparent in previous studies. The relationship derived for the successful transmission probability, throughput and average energy consumption, will provide better performance predictions. It will also offer greater insight into the strengths and weaknesses of the MAC operation, and possible enhancement opportunities.
Overall, the work presented in this thesis provides several significant insights into WSN performance improvements with both existing protocols and newly designed protocols.
Finally, some of the numerous challenges for future research are described.
46
Ferrigo, Samuel Francisco. "Momicare: um middleware móvel para smartphones para gerenciamento de uma rede de sensores sem fio corporais." Universidade do Vale do Rio dos Sinos, 2017. http://www.repositorio.jesuita.org.br/handle/UNISINOS/6631.
Testo completoAbstract (sommario):
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Previous issue date: 2017-08-03<br>Nenhuma<br>A Internet das Coisas, ou simplesmente IoT, apresenta inúmeras soluções para a área da
saúde. Diversos sensores podem ser colocados ao redor do corpo humano para monitoramento de seus sinais vitais e, a partir disso, prever problemas de saúde. Gerenciar esses sensores apresenta uma série de desafios que não são resolvidos pelos trabalhos relacionados pesquisados, como a busca pela eficiência energética na transmissão de dados, a segurança, a interoperabilidade e sincronização entre sensores que formam uma rede de sensores sem fio corporais. Uma solução para estes problemas é apresentada pelo modelo MOMICARE, um middleware móvel para smartphones para gerenciamento de uma rede de sensores sem fio corporais. O MOMICARE permite que um smartphone receba dados de diversos sensores, armazene-os e retransmita-os às aplicações médicas que necessitem usar esses dados, oferecendo baixo consumo de energia, segurança, independência de protocolos de redes de sensores sem fios e sincronismo entre os dados coletados pelos sensores. As principais contribuições científicas deste trabalho são a redução do consumo energético de dispositivos que formam uma rede Wireless Body Area Network, e o oferecimento de um sincronismo temporal entre os dados desses dispositivos.
O modelo foi analisado por meio da implementação de um protótipo e um ambiente de simulação, onde foram realizadas avaliações de: (1) consumo de energia dos dispositivos da
rede Wireless Body Area Network, (2) sincronização entre os dispositivos e o middleware, e (3) carga sobre o dispositivo onde o protótipo foi executado, considerando o uso de diversas aplicações simultâneas. Como resultados obtidos, verificou-se que, em dispositivos Bluetooth Low Energy, a redução no consumo de energia superou 10% em relação a aplicações convencionais, enquanto que em dispositivos padrão IEEE 802.15.4 a redução no consumo energético chegou a até 7,8%, quando comparado ao uso de aplicações convencionais. Outro resultado obtido foi a variação de sincronização inferior a 0,5 segundos, valores aceitáveis no que diz respeito a dispositivos médicos. Por fim, em todos os testes realizados, não foi verificado qualquer tipo de sobrecarga, sendo que a média de uso do processador apresentou valores médios inferiores a 1%.<br>The Internet of Things, or simply IoT, presents numerous solutions for the health area. Several
sensors can be placed around the human body to monitor your vital signs and, from there,
predict health problems. Managing these sensors presents a number of challenges that are not resolved by related research, such as the search for energy efficiency in data transmission, security, interoperability and synchronization between sensors that form a network of wireless body sensors. One solution to these problems is presented by the MOMICARE model, a mobile middleware for smartphones for managing a network of wireless body sensors. MOMICARE allows a smartphone to receive data from multiple sensors, store and re-transmit it to medical applications that need to use that data, offering low power consumption, security, wireless sensor network protocol independence and synchronization between data collected by sensors. The main scientific contributions of this work are the reduction of the energy consumption of devices that form a Wireless Body Area Network, and the offer of a temporal synchronism between the data of these devices. The model was analyzed through the implementation of a prototype and simulation environment, where evaluations were made of: (1) energy consumption ofWireless Body Area Network devices, (2) synchronization between devices and middleware, and 3) load on the device where the prototype was executed, considering the use of several simultaneous applications. As results obtained, it has been found that in Bluetooth Low Energy devices, the reduction in energy consumption exceeded 10% compared to conventional applications, whereas in standard devices IEEE 802.15.4 reduction in energy consumption reached up to 7.8%, when compared to the use of conventional applications. Another result obtained was the synchronization variation less than 0.5 seconds, acceptable values with respect to medical devices. Finally, in all the tests performed, no type of overload was verified, and the average use of the processor presented average values lower than 1%.
47
Nguyen, Theanh. "SHM through flexible vibration sensing technologies and robust safety evaluation paradigm." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/78632/5/Andy%20Nguyen%20Thesis.pdf.
Testo completoAbstract (sommario):
This research has successfully developed a novel synthetic structural health monitoring system model that is cost-effective and flexible in sensing and data acquisition; and robust in the structural safety evaluation aspect for the purpose of long-term and frequent monitoring of large-scale civil infrastructure during their service lives. Not only did it establish a real-world structural monitoring test-bed right at the heart of QUT Gardens Point Campus but it can also facilitate reliable and prompt protection for any built infrastructure system as well as the user community involved.
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Fiorilli, Luca. "Identificazione strutturale mediante l’algoritmo "Stochastic Subspace Identification - SSI"." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Cerca il testo completoAbstract (sommario):
Il presente elaborato affronta il problema del rilevamento dei danni strutturali nell’ambito dello Structural Health Monitoring (SHM) attraverso l’identificazione delle caratteristiche dinamiche delle strutture e con il solo utilizzo di vibrazioni ambientali. Questa procedura pertiene all’Operational Modal Analysis (OMA), campo dell’ingegneria che, tenendo conto della sola risposta del sistema senza conoscerne l’input, cattura i segnali nel dominio del tempo o della frequenza e identifica i parametri modali del sistema: frequenze naturali, indici di smorzamento e forme modali. Il successo di ogni metodo OMA dipende dalle caratteristiche dei segnali acquisiti, come la durata della loro registrazione o la frequenza di campionamento, e dal tipo di sistema di rilevamento, ad esempio la Wireless Sensor Network (WSN), rete meno costosa e più facile da realizzare rispetto a quella cablata, ma che registra un Time Synchronization Error (TSE) tra i clock dei suoi nodi sensore. Tra i metodi OMA, le tecniche Stochastic Subspace Identification (SSI) sono considerate tra le più potenti e affidabili nel dominio del tempo. Il nucleo di questo lavoro è la presentazione dei due approcci SSI, il Covariance-driven e il Data-driven, e il confronto tra le loro prestazioni, al fine di indagarne vantaggi e svantaggi anche attraverso la loro applicazione pratica. Viene studiata, in particolare, l’influenza della durata del segnale acquisito e dell’errore di sincronizzazione sulla precisione del calcolo delle proprietà dinamiche stimate con gli algoritmi SSI, che vengono poi confrontate con quelle ottenute grazie alla tecnica Frequency Domain Decomposition (FDD). Dai risultati numerici risulta che per ottenere una buona stima dei parametri modali si può ricorrere anche ad un segnale di breve durata e che il TSE ha un impatto negativo sul calcolo delle forme modali.
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Boem, Francesca. "Distributed Methods for Estimation and Fault Diagnosis: the case of Large-scale Networked Systems." Doctoral thesis, Università degli studi di Trieste, 2013. http://hdl.handle.net/10077/8534.
Testo completoAbstract (sommario):
2011/2012<br>L’obiettivo di questa tesi è il monitoraggio di sistemi complessi a larga-scala. L’importanza di questo argomento è dovuto alla rinnovata enfasi data alle problematiche riguardanti la sicurezza e l’affidabilità dei sistemi, diventate requisiti fondamentali nella progettazione. Infatti, la crescente complessità dei moderni sistemi, dove le relazioni fra i diversi componenti, con il mondo esterno e con il fattore umano sono sempre più importanti, implica una crescente attenzione ai rischi e ai costi dovuti ai guasti e lo sviluppo di approcci nuovi per il controllo e il monitoraggio. Mentre nel contesto centralizzato i problemi di stima e di diagnostica di guasto sono stati ampiamente studiati, lo sviluppo di metodologie specifiche per sistemi distribuiti, larga scala o “networked”, come i Cyber-Physical Systems e i Systems-of-Systems, è cominciato negli ultimi anni.
Il sistema fisico è rappresentato come l’interconnessione di sottosistemi ottenuti attraverso una decomposizione del sistema complesso dove le sovrapposizioni sono consentite. L’approccio si basa sul modello dinamico non-lineare dei sottosistemi e sull’approssimazione adattativa delle non note interconnessioni fra i sottosistemi.
La novità è la proposta di un’architettura unica che tenga conto dei molteplici aspetti che costituiscono i sistemi moderni, integrando il sistema fisico, il livello sensoriale e il sistema di diagnostica e considerando le relazioni fra questi ambienti e le reti di comunicazione. In particolare, vengono proposte delle soluzioni ai problemi che emergono dall’utilizzo di reti di comunicazione e dal considerare sistemi distribuiti e networked.
Il processo di misura è effettuato da un insieme di reti di sensori, disaccoppiando il livello fisico da quello diagnostico e aumentando in questo modo la scalabilità e l’affidabilità del sistema diagnostico complessivo. Un nuovo metodo di stima distribuita per reti di sensori è utilizzato per filtrare le misure minimizzando sia la media sia la varianza dell’errore di stima attraverso la soluzione di un problema di ottimizzazione di Pareto. Un metodo per la re-sincronizzazione delle misure è proposto per gestire sistemi multi-rate e misure asincrone e per compensare l’effetto dei ritardi nella rete di comunicazione fra sensori e diagnostici.
Poiché uno dei problemi più importanti quando si considerano sistemi distribuiti e reti di comunicazione è per l’appunto il verificarsi di ritardi di trasmissione e perdite di pacchetti, si propone una strategia di compensazione dei ritardi , basata sull’uso di Time Stamps e buffer e sull’introduzione di una matrice di consenso tempo-variante, che permette di gestire il problema dei ritardi nella rete di comunicazione fra diagnostici.
Gli schemi distribuiti per la detection e l’isolation dei guasti sono sviluppati, garantendo la convergenza degli stimatori e derivando le condizioni sufficienti per la detectability e l’isolability. La matrice tempo-variante proposta permette di migliorare queste proprietà definendo delle soglie meno conservative. Alcuni risultati sperimentali provano l’efficacia del metodo proposto.
Infine, le architetture distribuite per la detection e l’isolation, sviluppate nel caso tempo-discreto, sono estese al caso tempo continuo e nello scenario in cui lo stato non è completamente misurabile, sia a tempo continuo che a tempo discreto.<br>This thesis deals with the problem of the monitoring of modern complex systems. The motivation is the renewed emphasis given to monitoring and fault-tolerant systems. In fact, nowadays reliability is a key requirement in the design of technical systems. While fault diagnosis architectures and estimation methods have been extensively studied for centralized systems, the interest towards distributed, networked, large-scale and complex systems, such as Cyber-Physical Systems and Systems-of-Systems, has grown in the recent years. The increased complexity in modern systems implies the need for novel tools, able to consider all the different aspects and levels constituting these systems.
The system being monitored is modeled as the interconnection of several subsystems and a divide et impera approach allowing overlapping decomposition is used. The local diagnostic decision is made on the basis of the knowledge of the local subsystem dynamic model and of an adaptive approximation of the uncertain interconnection with neighboring subsystems.
The goal is to integrate all the aspects of the monitoring process in a comprehensive architecture, taking into account the physical environment, the sensor layer, the diagnosers level and the communication networks. In particular, specifically designed methods are developed in order to take into account the issues emerging when dealing with communication networks and distributed systems.
The introduction of the sensor layer, composed by a set of sensor networks, allows the decoupling of the physical and the sensing/computation topologies, bringing some advantages, such as scalability and reliability of the diagnosis architecture. We design the measurements acquisition task by proposing a distributed estimation method for sensor networks, able to filter measurements so that both the variance and the mean of the estimation error are minimized by means of a Pareto optimization problem. Moreover, we consider multi-rate systems and non synchronized measurements, having in mind realistic applications. A re-synchronization method is proposed in order to manage the case of multi-rate systems and to compensate delays in the communication network between sensors and diagnosers.
Since one of the problems when dealing with distributed, large-scale or networked systems and therefore with a communication network, is inevitably the presence of stochastic delays and packet dropouts, we propose therefore a distributed delay compensation strategy in the communication network between diagnosers, based on the use of Time Stamps and buffers and the definition of a time-varying consensus matrix. The goal of the novel time-varying matrix is twofold: it allows to manage communication delays, packet dropouts and interrupted links and to optimize detectability and isolability skills by defining less conservative thresholds.
The distributed fault detection and isolation schemes are studied and analytical results regarding fault detectability, isolability and estimator convergence are derived. Simulation results show the effectiveness of the proposed architecture.
For the sake of completeness, the monitoring architecture is studied and adapted to different frameworks: the fault detection and isolation methodology is extended for continuous-time systems and the case where the state is only partially measurable is considered for discrete-time and continuous-time systems.<br>XXV Ciclo<br>1985
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Řezáč, Martin. "Podpůrné algoritmy pro řízení elektrických motorů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-221272.
Testo completoAbstract (sommario):
This thesis is focused on a creating supporting drivers and algorithms for electrical motor control using CPU TriCore TC275 CA. The first part is devoted to processor description and selected peripherals, which are A/D converter, a timer for creating the PWM signals and the second timer for processing singnals from encoder. All drivers are tested on an aplication kit, which is equipped with TC275 CA processor. The second part analyzes the measurement quality of GMR sensor TLE5009. Special testbench was prepared for sin cos data capturing and for their comparison with precise encoder position measurement. It was composed from DC motor having both sensor types on commons shaft. Data are acquired using LabView. Subsequently, it analyzes the sensor data, their compensation and subsequent comparison with measured data from the encoder.