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1
Kaya, Zahit Evren. "Time Synchronization In Measurement Networks". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12611585/index.pdf.
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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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Behnam, Moris. "Hierarchical Real Time Scheduling and Synchronization". Licentiate thesis, Mälardalen University, School of Innovation, Design and Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-1324.
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The Hierarchical Scheduling Framework (HSF) has been introduced to enable compositional schedulability analysis and execution of embedded software systems with real-time constraints. In this thesis, we consider a system consisting of a number of semi-independent components called subsystems, and these subsystems are allowed to share logical resources. The HSF provides CPU-time to the subsystems and it guarantees that the individual subsystems respect their allocated CPU budgets. However, if subsystems are allowed to share logical resources, extra complexity with respect to analysis and run-time mechanisms is introduced. In this thesis we address three issues related to hierarchical scheduling of semi-independent subsystems. In the first part, we investigate the feasibility of implementing the hierarchical scheduling framework in a commercial operating system, and we present the detailed figures of various key properties with respect to the overhead of the implementation.
In the second part, we studied the problem of supporting shared resources in a hierarchical scheduling framework and we propose two different solutions to support resource sharing. The first proposed solution is called SIRAP, a synchronization protocol for resource sharing in hierarchically scheduled open real-time systems, and the second solution is an enhanced overrun mechanism.
In the third part, we present a resource efficient approach to minimize system load (i.e., the collective CPU requirements to guarantee the schedulability of hierarchically scheduled subsystems). Our work is motivated from a tradeoff between reducing resource locking times and reducing system load. We formulate an optimization problem that determines the resource locking times of each individual subsystem with the goal of minimizing the system load subject to system schedulability. We present linear complexity algorithms to find an optimal solution to the problem, and we prove their correctness
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Nakamura, Akira. "An investigation of real-time synchronization". Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321529.
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Yang, Hsueh-szu y Benjamin Kupferschmidt. "Time Stamp Synchronization in Video Systems". International Foundation for Telemetering, 2010. http://hdl.handle.net/10150/605988.
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ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, CaliforniaSynchronized video is crucial for data acquisition and telecommunication applications. For real-time applications, out-of-sync video may cause jitter, choppiness and latency. For data analysis, it is important to synchronize multiple video channels and data that are acquired from PCM, MIL-STD-1553 and other sources. Nowadays, video codecs can be easily obtained to play most types of video. However, a great deal of effort is still required to develop the synchronization methods that are used in a data acquisition system. This paper will describe several methods that TTC has adopted in our system to improve the synchronization of multiple data sources.
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Dong, Zhaoqing Sabrina 1977. "Hardware-assisted timer protocol for high resolution global time synchronization". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/86639.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (leaf 114).
by Zhaoqing Sabrina Dong.
M.Eng.
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Pallarés, Valls Oriol. "Time synchronization in underwater acoustic sensor networks". Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/403876.
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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.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.
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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.
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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.
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Troxel, Gregory D. (Gregory Donald). "Time surveying : clock synchronization over packet networks". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/34060.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (p. 165-166).
by Gregory D. Troxel.
Ph.D.
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Von, Zuben Francis S. G. y Alfred S. Jr David. "TIME SYNCHRONIZATION IN FLIGHT TEST DATA ANALYSIS". International Foundation for Telemetering, 2000. http://hdl.handle.net/10150/608278.
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International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, CaliforniaA recurring problem in flight testing navigation systems is the need for an accurate, common time reference for the system under test and for the truth source to which it is compared. Lockheed Martin Aeronautics Company and Computer Sciences Corporation have developed software that utilizes all available timing information to reference the times of validity for each navigation measurement to Coordinated Universal Time. This permits accurate comparison and correlation of data necessary for statistical error analysis of the navigation system.
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Mangalarapu, Chaitanya Kumar y Thamer Alyass. "Design & Implementation of Time Synchronization for Real-Time WirelessHART network". Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Data- och elektroteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-15575.
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Wireless technology has been regarded as a paradigm shifter in the processindustry. The first open wireless communication standard specifically designed forprocess measurement and control applications, WirelessHART (HighwayAddressable Remote Transducer) was officially released in September 2007 (as apart of HART 7 specification). Currently in industry the performance of machines are monitored in real-timescenario, which include from vibration measurement to surveillance monitoring.Sometimes data can be in the burst mode or sometimes it comes in a liner fashion.Therefore in order to achieve precise result an accurate time is mandatory. Various techniques and protocols are used and designed for the data collectionfrom different devices in industry located in different areas, among them isWirelessHART. WirelessHART networking is becoming popular for wirelesscommunication systems in industrial automation plants, which is a newlydeveloped protocol which is specifically designed to be used in industrialenvironment. The technique which has been used for data collection inWirelessHART is Time Synchronization and Channel Hooping (TSCH).However this technique sometimes has drawbacks and get failed when there is atransmutation of data in burst mode. Therefore the main object of this thesis work is to implement the Floodingtime Synchronization Protocol (FTSP) over Time Synchronization Protocol(TSCH) in WirelessHART communication standard.
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Lundqvist, Emil. "Timing and Synchronization over Ethernet". Thesis, Linköpings universitet, Institutionen för systemteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-115882.
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In this thesis an investigation will be done on how time and frequency can be synchronized over Ethernet with help of Precision Time Protocol and Synchronous Ethernet. The goal is to achieve a high accuracy in the synchronization when a topology of 10 cascaded nodes is used. Different approaches may be used when implementing Precision Time Protocol for synchronization. They will be investigated and the best approach for a good accuracy will be proposed. Another question that this thesis will cover is how to recover a radio frequency, a multiple of 3.84 MHz from Ethernets 10.3125 GHz. By using hardware support for the timestamps and transparent clocks in the forwarding nodes the best accuracy is achieved for the time and phase synchronization. Combining this with Synchronous Ethernet for frequency synchronization, to get a traceable clock through the system, will lead to the best result. The total error does not need to be greater than 1.46~ns if the asymmetry in the medium is neglected and a welldesigned PCS and FIFO are used. Recovering the radio frequency from Ethernet is done by using the highest common frequency, either an integer phase locked loop or a fractional phase locked loop can be used. The fractional phase locked loop will give a better result but will contribute with spurs that the integer phase locked loop does not.
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Leuhusen, Joakim y Andreas Karlsson. "Simulation and synchronization of distributed real-time systems". Thesis, Linköping University, Vehicular Systems, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-52784.
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Today we are very much dependent on different kinds of real time systems. Usually,a real time system is a system which is interacting with a physical environmentwith sensors or activators. There are many advantages by replacing mechanicalcomponents with electrical ones. For instance, it is usually cheaper and possibleto add new functions to the device without replacing the electronic part, whichwould have been necessary with a mechanical one.The possibility of simulating a distributed system is used throughout the vehi-cle industry. With the simulation of connected sub systems, using modeled busesand real time kernels, one could increase the correctness of the behavior of the sys-tem and consequently decrease the amount of time spent later in the developingprocess.In this master thesis we used modeled CAN-buses and real time models tosimulate the connection and execution time of the systems. The simulation resultsare used to validate the functionality of the distributed system. Additionally, aworst-case response time analysis is made to set timing constraints on the systemto fulfill given deadlines.During the work, different settings of the network are tested to analyze thesystem frequency needed to sustain deadlines and correctness on the network.
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Bergner, André. "Synchronization in complex systems with multiple time scales". Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5340/.
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In the present work synchronization phenomena in complex dynamical systems exhibiting multiple time scales have been analyzed. Multiple time scales can be active in different manners. Three different systems have been analyzed with different methods from data analysis.
The first system studied is a large heterogenous network of bursting neurons, that is a system with two predominant time scales, the fast firing of action potentials (spikes) and the burst of repetitive spikes followed by a quiescent phase. This system has been integrated numerically and analyzed with methods based on recurrence in phase space. An interesting result are the different transitions to synchrony found in the two distinct time scales. Moreover, an anomalous synchronization effect can be observed in the fast time scale, i.e. there is range of the coupling strength where desynchronization occurs.
The second system analyzed, numerically as well as experimentally, is a pair of coupled CO₂ lasers in a chaotic bursting regime. This system is interesting due to its similarity with epidemic models. We explain the bursts by different time scales generated from unstable periodic orbits embedded in the chaotic attractor and perform a synchronization analysis of these different orbits utilizing the continuous wavelet transform. We find a diverse route to synchrony of these different observed time scales.
The last system studied is a small network motif of limit cycle oscillators. Precisely, we have studied a hub motif, which serves as elementary building block for scale-free networks, a type of network found in many real world applications. These hubs are of special importance for communication and information transfer in complex networks. Here, a detailed study on the mechanism of synchronization in oscillatory networks with a broad frequency distribution has been carried out. In particular, we find a remote synchronization of nodes in the network which are not directly coupled. We also explain the responsible mechanism and its limitations and constraints. Further we derive an analytic expression for it and show that information transmission in pure phase oscillators, such as the Kuramoto type, is limited. In addition to the numerical and analytic analysis an experiment consisting of electrical circuits has been designed. The obtained results confirm the former findings.In der vorliegenden Arbeit wurden Synchronisationsphänomene in komplexen Systemen mit mehreren Zeitskalen untersucht. Es gibt mehrere Möglichkeiten wie diese verschiedenen Zeitskalen vorkommen können. Drei verschiedene Systeme, jedes mit einer anderen Art von zeitlicher Multiskalität, wurden mit unterschiedlichen Methoden der Datenanalyse untersucht. Das erste untersuchte System ist ein ausgedehntes heterogenes Netzwerk von Neuronen mit zwei dominanten Zeitskalen, zum einen die schnelle Folge von Aktionspotenzialen und zum anderen einer abwechselnden Folge von einer Phase von Aktionspotenzialen und einer Ruhephase. Dieses System wurde numerisch integriert und mit Methoden der Phasenraumrekurrenz untersucht. Ein interessantes Ergebnis ist der unterschiedliche Übergang zur Synchronisation der Neuronen auf den beiden verschiedenen Zeitskalen. Des weiteren kann auf der schnellen Zeitskala eine anomale Synchronisation beobachtet werden, d.h. es gibt einen Bereich der Kopplungsstärke in dem es zu einer Desynchronisation kommt. Als zweites wurde, sowohl numerisch als auch experimentell, ein System von gekoppelten CO₂ Lasern untersucht, welche in einem chaotischen bursting Modus arbeiten. Dieses System ist auch durch seine Äquivalenz zu Epidemiemodellen interessant. Wir erklären die Bursts durch unterschiedliche Zeitskalen, welche durch in den chaotischen Attraktor eingebettete instabile periodische Orbits generiert werden. Wir führen eine Synchronisationsanalyse mit Hilfe der kontinuierlichen Wavelettransformation durch und finden einen unterschiedlichen Übergang zur Synchronisation auf den unterschiedlichen Zeitskalen. Das dritte analysierte System ist ein Netzwerkmotiv von Grenzzyklusoszillatoren. Genauer handelt es sich um ein Nabenmotiv, welches einen elementaren Grundbaustein von skalenfreien Netzwerken darstellt, das sind Netzwerke die eine bedeutende Rolle in vielen realen Anwendungen spielen. Diese Naben sind von besonderer Bedeutung für die Kommunikation und den Informationstransport in komplexen Netzwerken. Hierbei wurde eine detaillierte Untersuchung des Synchronisationsmechanismus in oszillatorischen Netzwerken mit einer breiten Frequenzverteilung durchgeführt. Insbesondere beobachten wir eine Fernsynchronisation von Netzwerkknoten, die nur indirekt über andere Oszillatoren miteinander gekoppelt sind. Wir erklären den zu Grunde liegenden Mechanismus und zeigen dessen Grenzen und Bedingungen auf. Des weiteren leiten wir einen analytischen Ausdruck für den Mechanismus her und zeigen, dass eine Informationsübertragung in reinen Phasenoszillatoren, wie beispielsweise vom Kuramototyp, eingeschränkt ist. Diese Ergebnisse konnten wir durch Experimente mit elektrischen Schaltkreisen bestätigen.
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Paladugula, Prashanth. "Distributed network time synchronization using pseudo noise code". Thesis, Wichita State University, 2013. http://hdl.handle.net/10057/6831.
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In recent years, distributed network systems have been studied in order to yield a higher
data rate. However, performance of a distributed network degrades drastically when all nodes are
not properly synchronized. This thesis discusses the practical issues involved in existing
distributed network synchronization algorithms, and proposes an alternative solution for time
synchronization in distributed networks using a pseudo noise (PN) code. The proposed algorithm
has the following advantages over the existing algorithm: (1) increased time width of the pulseshaping
filter, i.e., narrowband waveform-shaping filter; (2) ability to work under a lower signalto-
noise ratio; (3) capability of reaching a steady state with fewer iterations; and (4) lower
steady-state error and fewer samples required per one update interval. Chapter 6 will elaborate
and explain these advantages. Simulation results will show the effectiveness of the algorithm
proposed and the advantages of the proposed algorithm over existing algorithms.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science
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El, Shazli Abdalla. "The synchronization of time-slotted photonic star networks /". Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99759.
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Photonics is a technology capable of supporting very high bit-rates of data. However, with the current state of photonic technologies logic and memory functions are very difficult to implement in the photonic domain. In photonic star networks using time division multiplexing (such as the Agile All Photonic Network), timeslots from the edges of the network have to arrive at the star point at exactly the same instant to be switched because they cannot be buffered in the photonic domain. The switching requires that the time at which the timeslots are transmitted must be coordinated and tightly controlled. This thesis addresses methods of synchronizing the components at the edge of the network to compensate for heterogeneous propagation delays between the edges and the star point. Different methods of providing this compensation are described and assessed in terms of their capabilities and performance.
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Pang, Albert. "A study on the time warp synchronization mechanism". Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22669.
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In this thesis, we present a brief introduction to distributed systems and highlight the issue of synchronization among processors in such a system. Traditionally, synchronization among processors in a multiprocessor system is achieved by conservative methods, based on block-resume mechanisms. Recently, an optimistic approach based on the virtual time paradigm, more commonly known as the time warp mechanism, has received a great deal of attention.In recent years, considerable work has been published describing how these systems are implemented, however, the performance analyses of such systems are lacking. In this thesis, we present several performance analyses which include, the analytical solution of a simple two processor system and the analysis of a homogeneous multiprocessor system. We also present performance analysis of a simple heterogeneous, multiprocessor time warp system, by simulations. In general, we find that the overall performance degrades as the system becomes more and more heterogeneous.
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Gagnon, Pascal. "Clock Synchronization Through Time-Variant Underwater Acoustic Channels". Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/17368.
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Approved for public release; distribution is unlimitedThe goal of this work is to develop methodologies for synchronizing the clocks of neighboring nodes of an underwater acoustic network. Clock synchronization requires an estimate of the signaling time delay between the nodes, which is particularly challenging in the presence of multipath propagation through the acoustic communication channel. This thesis focuses on modeling the underwater acoustic communication channel, accounting for the multipath arrivals, and creating a set of signal processing algorithms for estimating the required delay times that enable clock synchronization protocols for the underwater acoustic network. The proposed method involves correlating the responses of the bidirectional channels to exploit the underlying reciprocity. Performed in two stages, a sequence of probe signals is first transmitted to create an ensemble, which contains information about the time-variability of the acoustic communication channel with multipath. From this ensemble, we determine its dominant time-invariant characteristic and use it as a reference datum for the time delay measurements. The second stage consists in performing time-delay estimation of two probe signals exchanged between nodes. The two stages are tested using simulated signal measurements, and actual signal measurements were performed in a fresh-water lake for the first phase only. Both computer simulations and experimental results show the effectiveness of the proposed techniques.
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LoCascio, Marc Bayard. "Audio time compansion for studio and performance synchronization". Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/76155.
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Berg, Dale E. y Perry J. Robertson. "PRECISE TIME SYNCHRONIZATION DATA ACQUISITION WITH REMOTE SYSTEMS". International Foundation for Telemetering, 1998. http://hdl.handle.net/10150/609234.
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International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, CaliforniaResearchers at the National Wind Technology Center have identified a need to acquire data on the rotor of an operating wind turbine at precisely the same time as other data is acquired on the ground or a non-rotating part of the wind turbine. The researchers will analyze that combined data with statistical and correlation techniques to clearly establish phase information and loading paths and insights into the structural loading of wind turbines. A data acquisition unit has been developed to acquire the data from the rotating system at precise universal times specified by the user. The unit utilizes commercial data acquisition hardware, spread-spectrum radio modems, and a Global Positioning System receiver; and a custom-built programmable logic device. A prototype of the system is now operational, and initial field deployment is anticipated this summer.
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Mkacher, Faten. "Optimization of Time Synchronization Techniques on Computer Networks". Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALM015.
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De nos jours, alors que la société est toujours plus interconnectée, une synchronisation temporelle sûre et précise devient de plus en plus critique pour de nombreuses applications. Les dispositifs informatiques utilisent souvent des oscillateurs à cristal de faible précision pour conserver le temps en local. Cette imprécision engendre une dérive entre les machines. La solution pour assurer une synchronisation précise de l’heure entre elles est d’utiliser une horloge de référence avec une source précise de temps, puis de diffuser le temps sur le réseau. Un des protocoles qui assurent la synchronisation temporelle est Network Time Protocol (NTP). Bien que NTP ait bien fonctionné pour un usage général pendant de nombreuses années, sa sécurité et sa précision sont mal adaptées aux défis futurs. De nombreux mécanismes de sécurité dépendent du temps dans le cadre de leur fonctionnement. Par exemple, avant d’utiliser un certificat électronique,il est nécessaire de confirmer sa validité temporelle. Une machine avec une horloge imprécise pourrait accepter des certificats expirés ou révoqués.Cette thèse présente d’abord le contexte de la synchronisation temporelle en commençant par la définition de certains concepts fondamentaux tels que le modèle d’horloge, le problème de la synchronisation d’horloge et certaines notions comme l’exactitude, la précision et la stabilité des horloges.Nous étudions les protocoles de synchronisation temporelle les plus courants des réseaux de communication, et entre autres NTP.Ensuite, nous considérons la sécurité de la synchronisation temporelle en présentant les possibles menaces de sécurité contre les protocoles de synchronisation temporelle et les exigences de sécurité de ces protocoles. Nous nous concentrons sur la sécurité du protocole NTP tel que décrit par le standard, et les travaux connexes qui ont tenté de l’améliorer sur ce point. Nous discutons également de l’importance d’avoir un compromis bien équilibré entre sécurité et performance.Dans notre première contribution, nous proposons d’aller plus loin que NTP avec Secure Time Synchronization Protocol (STS), un nouveau protocole de synchronisation de l’heure, qui est authentifié et sécurisé, et adapté aux larges déploiements. Nous décrivons le fonctionnement de STS et prouvons sa conception sécurisée, à l’aide d’une analyse formelle faite par deux outils de vérification de protocole de sécurité : Proverif et Tamarin. Nous présentons l’implémentation de STS basée sur le projet OpenNTPD, et évaluons ses performances en comparant la précision de STS avec celle de NTP non authentifié. Nous soulignons la dépendance circulaire entre la validation du certificat et la synchronisation temporelle.En réalité, une synchronisation temporelle fiable nécessite des matériaux cryptographiques qui ne sont valables que sur des intervalles de temps désignés, mais ces intervalles de temps ne peuvent être comparés à l’heure actuelle que lorsque les hôtes participants sont synchronisés de manière fiable. Nous présentons une solution qui fournit, lors de l’amorçage, une synchronisation approximative basée sur le blockchain Bitcoin, pour rompre cette dépendance circulaire.Dans notre deuxième contribution, nous proposons une méthode pour améliorer l’exactitude du protocole NTP, en tenant compte des délais de transmission asymétriques dus à une bande passante ou à un routage différent sur le chemin d’aller et de retour. En fait, l’asymétrie est assez répandue sur Internet, ce qui dégrade la performance de NTP qui fait l’hypothèse de délais symétriques. Cette méthode s’appuie sur l’utilisation d’un client NTP synchronisé par GPS, pour mesurer le délai unidirectionnel minimal aller et retour jusqu’à son serveur de temps. Ainsi, il est possible de calibrer NTP en prenant en compte cette asymétrieNowadays, as society has become more interconnected, secure and accurate time-keeping becomes more and more critical for many applications. Computing devices usually use crystal clocks with low precision for local synchronization. These low-quality clocks cause a large drift between machines. The solution to provide precise time synchronization between them is to use a reference clock having an accurate source of time and then disseminate time over a communication network to other devices. One of the protocols that provide time synchronization over packet-switched networks is Network Time Protocol (NTP). Although NTP has operated well for a general-purpose use for many years, both its security and accuracy are ill-suitedfor future challenges. Many security mechanisms rely on time as part of their operation. For example, before using a digital certificate, it is necessary to confirmits time validity. A machine with an inaccurate clock canaccept an expired or revoked certificate.This thesis first provides a background on time synchronization starting with the definition of some fundamental concepts such as the clock model, the problem of clock synchronization, and some notions like accuracy, precision, and stability of clocks. We study the most common time synchronization protocols used in packet-switched networks, and among others NTP.Then,we consider the security of time synchronization by presenting the possible security threats against time synchronization protocols and the security requirements of these protocols. We zoom in the securityof the NTP protocol as described by the standard NTP and other related work that tried to enhance NTP security. We also discuss the importance of having a well-balanced trade-off between security and performance.In our first contribution, we propose to go further in the support of NTP security with Secure Time Synchronization protocol (STS), a new secure authenticated time synchronization protocol suitable for widespread deployments. We describe the operation of STS and prove its design secure with a formal analysis using two security protocol verification tools: Proverif and Tamarin. We present the implementation of STS based on the OpenNTPD project, and evaluate its performance by comparing the STS precision with unauthenticated NTP. We point out the circular dependency between certificate validation and time synchronization. In fact, reliable time synchronization requires cryptographic materials that are valid only over designated time intervals, but time intervals can be only enforced when participating hosts are reliably synchronized. We present a solution for bootstrapping time synchronization based on the Bitcoin blockchain to break this circular dependency.In our second contribution, we propose a method for improving the accuracy of the NTP protocol by taking into account asymmetric transmission delays due to different bandwidth or routing on the forward and backward paths. In fact, asymmetry is quite prevalent in the Internet, which leads to low accuracy ofNTP that relies on the symmetric delay assumption to compute the clock offset. This method builds on using an NTP client synchronized with GPS to measure precisely the one-way transmission delay on the forward and backward path with his time server. In this way, it is possible to calibrate NTP to take into account asymmetry
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Saravanos, Yanos. "Energy-Aware Time Synchronization in Wireless Sensor Networks". Thesis, University of North Texas, 2006. https://digital.library.unt.edu/ark:/67531/metadc5438/.
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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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Barnes, Richard Neil. "Global synchronization of asynchronous computing systems". Master's thesis, Mississippi State : Mississippi State University, 2001. http://library.msstate.edu/etd/show.asp?etd=etd-10262001-094922.
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Fahmy, Sherif Fadel. "Collaborative Scheduling and Synchronization of Distributable Real-Time Threads". Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/27578.
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In this dissertation, we consider the problem of scheduling and synchronization of distributable real-time threads --- Real-Time CORBA's first-class abstraction for programming real-time, multi-node sequential behaviors. Distributable real-time threads can be scheduled, broadly, using two paradigms: node independent scheduling, in which nodes independently construct thread schedules, based on node-level decomposition of distributable thread (or DT) scheduling parameters, and collaborative scheduling, in which nodes collaborate to construct system-wide thread schedules, which may or may not involve scheduling parameter decomposition.
While significant literature exists on node independent scheduling, little is known about collaborative scheduling and its concomitant tradeoffs. We design three collaborative scheduling algorithms, called ACUA, QBUA, and DQBUA. ACUA uses theory of consensus and QBUA uses theory of quorums for distributable thread schedule construction. DQBUA extends QBUA with lock-based, local and distributed concurrency control. The algorithms consider a model where distributable threads arrive arbitrarily, have time/utility function time constraints, access resources in an arbitrary way (e.g., arbitrary lock acquire/release order, arbitrary nestings), and are subject to arbitrary node crash failures and message losses.
We analytically establish several properties of the algorithms including probabilistic end-to-end termination time satisfactions, timeliness optimality during underloads, bounded exception handling time, and correctness of the algorithms in partially synchronous systems.
We implement distributable real-time threads in the Linux kernel as a first-class programming and scheduling abstraction. The resulting kernel, called ChronOS, provides application interfaces for creating and manipulating distributable threads, as well as kernel interfaces and mechanisms for scheduling them (using both independent and collaborative approaches). ChronOS also has failure detector mechanisms for detecting and recovering from distributable thread failures.
We implement the proposed scheduling algorithms and their competitors in ChronOS and compare their behavior. Our studies reveal that the collaborative scheduling algorithms are superior to independent scheduling algorithms for certain thread sets, in particular, when thread sections have significantly varying execution time. This variability, especially if the variability is not consistent among the threads, may cause each node to make conflicting decisions in the absence of global information. We observe that collaborative schedulers outperform independent schedulers (e.g., EDF augmented with PIP) in terms of accrued utility by as much as 75%.
We identify distributed dependencies as one of the major sources of overhead in collaborative scheduling. In particular, the cost of distributed lock-based concurrency control (e.g., lock management, distributed deadlock detection/resolution) can significantly reduce the problem space for which collaborative scheduling is beneficial. To mitigate this, we consider the use of software transactional memory (or STM), an optimistic, non-blocking synchronization alternative to lock-based concurrency control which has been extensively studied in non real-time contexts. We consider distributable real-time threads with STM concurrency control, and develop techniques for analyzing and bounding their end-to-end response times on distributed single-processor and distributed multiprocessor systems. We also develop contention management techniques, a key component of STM, which are driven by threads' real-time scheduling parameters, and establish their tradeoffs against non-real-time contention managers.Ph. D.
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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.
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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.
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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.
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Almas, Muhammad Shoaib. "Synchrophasor Applications and their Vulnerability to Time Synchronization Impairment". Doctoral thesis, KTH, Elkraftteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217978.
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Recent years have seen the significance of utilizing time-synchronized, high resolution measurements from phasor measurement units (PMUs) to develop and implement wide-area monitoring, protection and control (WAMPAC) systems. WAMPAC systems aim to provide holistic view of the power system and enable detection and control of certain power system phenomena to enhance reliability and integrity of the grid. This thesis focuses on the design, development and experimental validation of WAMPAC applications, and investigates their vulnerability to time synchronization impairment. To this purpose, a state-of-the-art real-time hardware-in-the-loop (RT-HIL) test-bench was established for prototyping of synchrophasor-based applications. This platform was extensively used throughout the thesis for end-to-end testing of the proposed WAMPAC applications. To facilitate the development of WAMPAC applications, an open-source real-time data mediator is presented that parses the incoming synchrophasor stream and provides access to raw data in LabVIEW environment. Within the domain of wide-area protection applications, the thesis proposes hybrid synchrophasor and IEC 61850-8-1 GOOSE-based islanding detection and automatic synchronization schemes. These applications utilize synchrophasor measurements to assess the state of the power system and initiate protection / corrective action using GOOSE messages. The associated communication latencies incurred due to the utilization of synchrophasors and GOOSE messages are also determined. It is shown that such applications can have a seamless and cost-effective deployment in the field. Within the context of wide-area control applications, this thesis explores the possibility of utilizing synchrophasor-based damping signals in a commercial excitation control system (ECS). For this purpose, a hardware prototype of wide-area damping controller (WADC) is presented together with its interface with ECS. The WADC allows real-time monitoring and remote parameter tuning that could potentially facilitate system operators’ to exploit existing damping assets (e.g. conventional generators) when changes in operating conditions or network topology emerges. Finally the thesis experimentally investigates the impact of time synchronization impairment on WAMPAC applications by designing RT-HIL experiments for time synchronization signal loss and time synchronization spoofing. It is experimentally demonstrated that GPS-based time synchronization impairment results in corrupt phase angle computations by PMUs, and the impact this has on associated WAMPAC application.QC 20171121
smart transmission grid operation and control (STRONg2rid)
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Behnam, Moris. "Synchronization Protocols for a Compositional Real-Time Scheduling Framework". Doctoral thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-10447.
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In this thesis we propose techniques to simplify the integration of subsystems while minimizing the overall amount of CPU resources needed to guarantee the schedulability of real-time tasks. In addition, we provide solutions to the problem of allowing for the use of logical resources requiring mutual exclusion. The contribution of the thesis is presented in three parts. In the first part, we propose a synchronization protocol, called SIRAP, to facilitate sharing of logical resources in a hierarchical scheduling framework. In addition, we extend an existing synchronization protocol, called HSRP, such that each subsystem can be developed independently. The performance of the proposed protocols is evaluated by extensive simulations. In the second part, we present an efficient schedulability analysis that exploits the lower scheduling overhead introduced by each of the proposed protocols. Finally, in the third part, we propose new methods and algorithms that find the optimal system parameters (e.g., optimal resource ceiling), that minimize the amount of CPU resources required to ensure schedulability, when using the proposed synchronization protocols in a hierarchical scheduling framework. The motivation of this work comes from an emerging industrial trend in embedded software systems development to integrate multiple applications (subsystems) on a small number of processors. The purpose of this integration is to reduce the hardware related costs as well as the communication complexity between processors. In this setting a large number of industrial applications face the problem of preserving their real-time properties after their integration onto a single processor. In addition, temporal isolation between the applications during runtime may be required to prevent failure propagation between different applications. Specifically, we propose a hierarchical scheduling framework that allows for a simplified integration of subsystems. The framework preserves the essential temporal characteristics of the subsystems, both when running in isolation as well as when they are integrated with other subsystems. In this thesis, we assume a model where a system consists of a number of subsystems. The subsystems can interact with each other using shared logical resources. The framework ensures that the individual subsystem respects its allocated share of the processor. The difficulty lies in allowing two or more subsystems to share logical resources, which introduces an additional complexity in the schedulability analysis and also increases the system load.
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Zhou, Hongyi. "Task scheduling and synchronization for multiprocessor real-time systems". Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/9178.
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Seetharaman, Surya. "Time Synchronization for Ethernet Communication based Line Differential Protection". Thesis, KTH, Elkraftteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214079.
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Most of the industrial manufactures and designers of Power Substation Automation ProtectionControl products are under pressure regarding the existing communication architecture ofthe Line Dierential Protection Application. Currently the widely used technologies includeSONET/SDH which are circuit switched networks, that are no longer predominant. They arebeen replaced with Packet Switched Networks everywhere. Moreover dedicated network equipmentis required to be maintained for using SDH/SONET technologies. Hence it is becomingincreasingly hard for the utilities to get access to and maintain the SDH/SONET networks.The main objective of this thesis work is to develop an alternative communication solutionin order to migrate away from these SDH/SONET networks. The project work is done suchthat the requirements for the Line Dierential Protection Communication are carefully analysedand a solution is designed such that it fulls those requirements. Following that the implementationand evaluation of the solution is performed. In the end, a testing of this solutionis also done on a real-time WAN network running the Line Dierential Protection function,in order to verify the working of the solution and study the challenges of a WAN deploymentscenario in future.De esta industriella tillverkare och designers till produkter av system for stationsautomation arunder press angaende den existerande kommunikationsarkitekturen for Linjedierentialskyddstillampningar. De for narvarande utbredda teknologierna som anvands, som SONET/SDH, arkretskopplade natverk vilket inte langre ar den dominerande natverksprincipen. Dessa ar pavagatt bli ersatta av paketformedlade natverk. Dessutom kravs det att dedikerad natverksutrustningmaste underhallas for att anvandas med SONET/SDH-teknologier. Darfor borjar det blikravande och svart for verktygen att ges atkomst samt underhalla SONET/SDH-natverk.Huvudmalet med denna uppsats ar att utveckla en alternativ kommunikationslosning i syfteatt byta ut dessa SDH/SONET-natverk. Arbetet ar utfort genom att forst noggrant analyserakraven for Linjedierentialskydds-kommunikation for att sedan nna och designa en losningsom uppfyller dessa krav. Darefter foljer en implementation och utvardering av den funnalosningen. I sista fasen genomfors en testning av losningen i ett realtids WAN-natverk somkor Linjedierentialskydds-funktionen, detta for att veriera hur den funna losningen fungerarsamt att studera utmaningar for en framtida WAN implementation.
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Di, Giuliantonio Andrea. "Data integration, real-time synchronization and RESTful Web Service". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8258/.
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Analisi e sviluppo di procedure di importazione dati per un integratore di annunci immobiliari dedicato alla vendita di soggiorni turistici in case vacanza. Il documento tratta inoltre l'implementazione di un Web Service conforme all'architettura RESTful per l'accesso e l'esportazione dei dati a soggetti terzi autorizzati tramite Digest Authentication.
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Bommakanti, Hemanth Ram Kartik. "Impact of Time Synchronization Accuracy in Integrated Navigation Systems". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-260239.
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Global Navigation Satellite System/Inertial Measurement Unit (GNSS/IMU) Integrated Navigation Systems (INS) integrate the positive features of GNSS and IMU for optimal navigation guidance in high accuracy outdoor navigation systems, for example using Extended Kalman Filter (EKF) techniques. Time synchronization of IMU data with precise GNSS based time is necessary to accurately synchronize the two systems. This must be done in real-time for time sensitive navigation applications such as autonomous vehicles. The research is done in two parts. The first part is the simulation of inaccurate time-stamping in a single axis of nonlinear input data in a gyroscope and an accelerometer, to obtain the timing error value that is tolerable by a high accuracy GNSS/INS system. The second part is the creation of a real-time algorithm using an STM32 embedded system enabled with FreeRTOS real-time kernel for a GNSS receiver and antenna, along with an IMU sensor. A comparative analysis of the time synchronized system and an unsynchronized system is done based on the errors produced using gyroscope and accelerometer readings along a single axis from the IMU sensor, by conducting static and rotational tests on a revolving chair.The simulation concludes that a high accuracy GNSS/INS system can tolerate a timing error of up to 1 millisecond. The real-time solution provides IMU data paired with updated GNSS based time-stamps every 5 milliseconds. The timing jitter is reduced to a range of ±1 millisecond. Analysis of final angular rotation error and final position error from gyroscope and accelerometer readings respectively, indicate that the real-time algorithm produces a reduction in errors when the system is static, but there is no statistical evidence showing the reduction of errors from the results of the rotational tests.GNSS / IMU integrerade navigationssystem kombinerar de positiva egenskaperna hos GNSS och IMU för optimal prestanda i noggranna navigationssystem. Detta görs med hjälp av sensorfusion, till exempel EKF. Tidssynkronisering av IMU-data med exakt GNSS-baserad tid är nödvändigt för att noggrant synkronisera de två systemen. Detta måste göras i realtid för tidskänsliga navigationsapplikationer såsom autonoma fordon. Forskningen görs i två delar. Den första delen är simulering av icke-linjär rörelse i en axel med felaktig tidsstämpling hos ett gyroskop och en accelerometer. Detta görs för att erhålla det högsta tidsfel som är acceptabelt hos ett GNSS / INS-system med hög noggrannhet. Den andra delen är skapandet av en realtidsalgoritm med ett inbyggt STM32-system med FreeRTOS som realtidskärna för en GNSSmottagare och antenn, tillsammans med en IMU-sensor. En jämförande analys av det tidssynkroniserade systemet mot ett osynkroniserat system görs baserat på de positionsfel längs en axel som produceras av gyroskopoch accelerometermätningar. Detta görs genom att utföra statiska och roterande tester med hjälp av en roterande stol.Simuleringen visar att ett noggrant GNSS / INS-system tolererar ett tidsfel på upp till 1 millisekund. Realtidslösningen ger IMU-data med tidsstämplar synkroniserade med GNSS-tid var femte millisekund. Tidsjittret reduceras till ett intervall mellan ± 1 millisekund. Analysen av det slutliga vinkelrotationsfelet och positionsfelet från gyroskopoch accelerometermätningar indikerar att realtidsalgoritmen ger ett lägre fel när systemet är statiskt. Det finns dock inga statistiska bevis för förbättringen från resultaten av rotationstesterna.
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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.
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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.
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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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Sze, Hoi-yee Esther y 施凱兒. "The relationship between rhythmic synchronization and response inhibition". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B48691045.
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Temporal preparation and impulsivity are sharing two common cognitive processes: time perception and response inhibition. Rhythmic synchronization can be regarded as a specific paradigm of temporal preparation. The major purpose of the present study is to examine the relationship between rhythmic synchronization and response inhibition. Results indicated a significant correlation between rhythmic synchronization and response inhibition. Number of years of formal music training was not significantly correlated with rhythmic synchronization. No relationship was found between response inhibition and general intelligence.
Regression analysis revealed that number of commission errors was the best predictor for rhythmic synchronization, followed by reaction time of interference. Time perception is anticipatory in nature and should be better examined with a proactive stopping paradigm. Response style was not found to have a statistical significant role in the present study. Further research may further examine the clinical effectiveness of rhythmic synchronization on alleviating impulsivity via its effect on response inhibition.
proactive stopping paradigm. Response style was not found to have a statistical significant role in the present study. Further research may further examine the clinical effectiveness of rhythmic synchronization on alleviating impulsivity via its effect on response inhibition.published_or_final_version
Clinical Psychology
Doctoral
Doctor of Psychology
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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/.
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Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: distributed beamforming; carrier synchronization; software-defined-radio; sensor networks; wireless networks; cooperative transmission; virtual antenna arrays. Includes bibliographical references (leaves 168-169).
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Scherman, Andreas. "Extending the Scope of Compile-time Optimizations Across Synchronization Operations". Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-333028.
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With the rise of multiprocessor computers, parallel computing has become a necessity in order to achieve high performance. Modern compilers are conservative in applying classical compiler optimizations to parallel programs, as the compiler might require expensive whole-code analysis in order to preserve the semantics and correctness of the code, to ensure no data races are introduced through optimizations. Extended data-race-free regions (xDRF) is a compile-time analysis that gives the guarantee that variables accessed within the xDRF region cannot be modified by other threads. This guarantee enables safe traditional compiler optimizations on larger regions of code. The extended data-race free regions are used to make stronger alias analysis statements, which allows the traditional compiler optimizations to use the information gained from the extended data-race-free analysis directly without any other changes of the optimization step. Results show a varied utilization of the extended data-race-free, with two out of seventeen benchmarks being unable to find any extended data race-free region, and one benchmark having as many as 23 regions. Usingthe xDRF analysis, the compiler was able to increase by up to 2% the number of load instructions hoisted or deleted. No benchmark show a consistent run-time improvement from the additional transformations. Future work will focus on expanding the usage of the xDRF analysis, forexample for improving Capture Tracking and Escape Analysis, which we expect will lead to a run-time improvement.
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Klukas, Richard Walter. "A superresolution based cellular positioning system using GPS time synchronization". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0021/NQ47925.pdf.
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Lee, Seung Yong. "A Framework for Real-time Synchronization in Intelligent Media Generators". NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-03312004-191928/.
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Recent advances in computer graphics and multimedia technologies have contributed to the development of interactive media-rich systems that generate media elements dynamically in multiple modalities to present information in an effective and appealing manner to users. Utilizing media elements in an application that requires them to be temporally coordinated in real-time presents synchronization issues because the wrong timing or duration of media elements will be easily detected by the user. Most media-rich systems have solved various aspects of the media element synchronization problem. However, they have done so in an ad hoc manner without providing a generic reusable framework. This thesis proposes a framework for real-time synchronization in intelligent media generators. Our research addresses six primary issues that are essential to creating media-rich systems that do not utilize an ad hoc solution to their media element synchronization problems: synchronization of media elements, decoupling high-level and low-level processing, extensibility, media element sequencing, real-time performance, and domain-independence. The framework has been implemented in an agent-based multimedia generator for an intelligent tutoring system to demonstrate its feasibility.
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Åsberg, Mikael. "Synthesis and Synchronization Support for Hierarchically Scheduled Real-Time Systems". Doctoral thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-23462.
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A piece of software, that we define as a software system, can consist of anything from a few lines of program code or the entire software stack in a vehicle. Software systems can be divided into smaller and partially independent parts called subsystems/partitions (we use the words partition and subsystem interchangeably). The non-functional isolation of subsystems, that appears when the software system is hierarchically divided, has great advantages when it comes to preventing fault propagation between subsystems. The hierarchical division, that we refer to as hierarchical scheduling, has other advantages as well. It facilitates re-usability and it makes timing analysis of software systems easier. Hierarchical scheduling has been shown to be a useful tool in counteracting the verification challenges that comes from the growing complexity in software. For example, the avionics-specification ARINC653 and the safety-critical operating systems seL4 and PikeOS safely divide resources for independent safety-critical applications by using hierarchical scheduling. Hierarchical scheduling can be implemented in many different ways, depending on what resource that is supposed to be shared among applications. The resource could be the CPU, memory, network etc. The work in this thesis is focused on the practical aspects of timing isolation among subsystems, i.e., sharing of the CPU resource. Hence, this work elaborates on how to adapt and extend the operating-system task-scheduler to support hierarchical scheduling. We have focused on both independent and semi-dependent subsystems. Independent subsystems only share general resources such as the CPU and memory. Semi-independent subsystems share not only the general resources, but also other logical resources that can only be accessed in a mutually exclusive way, i.e., by one subsystem at a time. An example of such a resource could be a shared memory-space, e.g., a database, a memory-mapped device etc. This thesis has two main parts related to hierarchical scheduling: scheduler synthesis, and synchronization. Scheduler synthesis is related to implementation and design strategies when adding support for hierarchical scheduling in an operating system. We have focused on various operating systems that were lacking the feature of hierarchical scheduling. The two most interesting operating systems that we worked on was Linux and seL4. These two operating systems represent two extremes, where Linux is more focused towards soft real-time systems and seL4 towards pure hard real-time (safety-critical) systems. Linux-based systems have in general less strict demands on correctness and more requirements on usability. Usability implies less installation efforts and less limitations in the usage of the available Linux functionality. The usability aspect is especially important for Linux systems since kernel updates occur much more frequently compared to any other operating system. Hence, extending/modifying the functionality of Linux must be done in a way that does not require any modifications to the kernel. seL4 on the other hand has strict requirements on safety, i.e., functional and non-functional correctness, but also performance efficiency. Guaranteeing correctness implies a potential loss of performance due to the added overhead that the verified software can bring. The correctness aspect includes strategies on how to verify hierarchical schedulers, but also how to minimize the scheduler overhead and achieve as good run-time performance as possible. Conclusively, there are many challenges when it comes to scheduler synthesis. There are requirements on performance, usability, correctness etc. The contribution in the synthesis part includes a scheduler framework called ExSched (External Scheduler). We have also contributed with a novel approach to verify hierarchical schedulers, and a code generator called TAtoC (Timed Automata to C) which contributes to the effective run-time performance of synthesized timed-automata models. The second part of this thesis, synchronization, is an important general aspect of hierarchically scheduled systems since the isolation of subsystems makes resource sharing among subsystems more challenging. We have advanced the state-of-the-art in this research area by introducing a new synchronization protocol called RRP (Rollback Resource Policy) that improves on the robustness and run-time performance compared to the existing protocols. We have also conducted a large scale experimental evaluation of all existing protocols that we have implemented in the widely used real-time operating system VxWorks.
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Bates, Lakesha. "ANALYSIS OF TIME SYNCHRONIZATION ERRORS IN HIGH DATA RATE ULTRAWIDEBAN". Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2582.
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Emerging Ultra Wideband (UWB) Orthogonal Frequency Division Multiplexing (OFDM) systems hold the promise of delivering wireless data at high speeds, exceeding hundreds of megabits per second over typical distances of 10 meters or less. The purpose of this Thesis is to estimate the timing accuracies required with such systems in order to achieve Bit Error Rates (BER) of the order of magnitude of 10-12 and thereby avoid overloading the correction of irreducible errors due to misaligned timing errors to a small absolute number of bits in error in real-time relative to a data rate of hundreds of megabits per second. Our research approach involves managing bit error rates through identifying maximum timing synchronization errors. Thus, it became our research goal to determine the timing accuracies required to avoid operation of communication systems within the asymptotic region of BER flaring at low BERs in the resultant BER curves. We propose pushing physical layer bit error rates to below 10-12 before using forward error correction (FEC) codes. This way, the maximum reserve is maintained for the FEC hardware to correct for burst as well as recurring bit errors due to corrupt bits caused by other than timing synchronization errors.M.S.E.E.
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical Engineering
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PENARANDA, FABIAN ARTURO CASTILLA. "VEHICLE ROUTING PROBLEMS WITH TIME WINDOWS AND EXACT SYNCHRONIZATION CONSTRAINTS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2013. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=23834@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE EXCELENCIA ACADEMICA
Uma generalização do problema de roteamento de veículos (VRP) presente em aplicações práticas em portos e operações em minas é o objeto desta dissertação. Nesta variante do VRP cada cliente pode demandar diferentes tipos de veículos para cumprir tarefas colaborativamente. Nesta atividade, os veículos podem aguardar o início da operação no local porém, devem iniciar as tarefas ao mesmo tempo. O objetivo é determinar as rotas dos veículos disponíveis de modo a maximizar a soma (ponderada) dos clientes atendidos enquanto a distância total percorrida é minimizada. O caso específico onde todos os clientes são atendidos e a distância total percorrida é minimizada determina o problema central estudado nessa dissertação. Este caso particular pode ser visto como uma generalização direta do, muito estudado e conhecido problema de roteamento, VRP com janelas de tempo (VRPTW) onde a capacidade dos veículos é suficientemente grande. Esta escolha de um problema mais restrito é justificada por permitir uma clara comparação de sua dificuldade através da sua relação com o VRPTW. A partir da classificação dos casos de sincronização em problemas de roteamento proposta por (DREXL, 2012), denominamos o problema aqui estudado de Problema de Roteamento de Veículos com Janelas de Tempo e Sincronização exata da Operação (VRPTWEOS). Neste trabalho damos uma definição formal ao VRPTWEOS. Modelos de programação inteira são propostos e analisados. Também apressentamos métodos de resolução baseados na decomposição Dantzig-Wolfe, dos quais são derivados algoritmos exatos e aproximados. Com o propósito de avaliar a eficiencia desses algoritmos, foi criado um grupo de instancias de teste baseado no benchmark do Solomon para o VRPTW. O método usado para criar o conjunto de instancias de teste é descrito em detalhe. Experimentos computacionais sobre este conjunto de instancias mostraram que o método de resolução proposto é promissor para a resolução do VRPTWEOS.
This dissertation addresses a generalization of the vehicle routing problem (VRP) that arises in real life applications in ports and mine operations. In this VRP variant, each customer may demand different types of vehicles to perform a task collaboratively. Vehicles are allowed to wait at the locations but they must start operating at the same time. The objective is to route the available vehicles while maximizing the (weighted) sum of served customers and minimizing the total distance traveled. The specific case where all customers must be served while minimizing the total distance traveled is the central problem here studied. This special case can be viewed as a straightforward generalization of, a well known and more specific routing problem, the VRP with time windows (VRTPTW) where the capacity of the vehicles is sufficiently large. We support this narrower scope by stating that it allows a clear comparison of the problem hardness by its relation to the VRPTW. Sticking to the classification of synchronization in vehicle routing proposed by (DREXL, 2012) we named this problem as the Vehicle Routing Problem with Time Windows and Exact Operation Synchronization (VRPTWEOS). In this work, a formal definition for the VRPTWEOS is provided. Integer programming models for this problem are proposed and analyzed. Furthermore, we propose a solution method based on the Dantzig-Wolfe decomposition for which exact and aproximated resolution algorithms are described. In order to test the performance of those algorithms, a group of benchmark instances for the VRPTWEOS was created on top of the Solomon benchmark for the VRPTW. The method used to create the benchmark instances is described in detail. Computational experiments over the mentioned set of instances showed that the proposed solution approach is a promising alternative for solving the VRPTWEOS.
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Maia, Marcos Daniel Nogueira. "Synchronization and control in networks with strongly time-delayed couplings". Instituto Nacional de Pesquisas Espaciais (INPE), 2017. http://urlib.net/sid.inpe.br/mtc-m21b/2017/09.12.20.07.
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The stability of synchronization and control in networks of dynamical systems with strongly delayed connections is investigated. Strict conditions for both, synchronization of stable periodic and equilibrium solutions , and control of unstable equilibrium are obtained. With a network model including self-feedback delay, the existence of a critical coupling strength kc is demonstrated, which is related to the network structure, isolated vector field and coupling function, such that for large delay and coupling strength k < kc the network undergoes to stable synchronization. Moreover, it is derived that for heterogeneous networks, kc $\rightarrow$ 0 as the network size grows to infinity, unless the coupling parameter scales with the maximum degree. In contrast, for random networks, the interval of coupling strengths that leads to stable synchronization is the maximum possible when the connectivity threshold is crossed making the network connected. Based on the network structure, the scaling of the coupling parameter, which allows for a synchronization, is derived. And, with a network model consisting of instantaneous self-connections, it is shown that it is possible to stabilize synchronous equilibrium that is unstable in an isolated system. Such a control close to a Hopf bifurcation is studied in details and strict conditions for the stability are obtained. In particular, it is demonstrated that the stabilization domains in parameter space are reappearing periodically and decreasing in size with the increase of time-delays. Also, the frequency of the reappearance of the control domains and the number spectral roots of the adjacency matrix are closely dependent, for instance, the number of cycle multi-partitions of the graph indicates the reappearance frequency of the control domains.Nesta tese investiga-se a estabilidade da sincronização e o controle em redes de sistemas dinâmicos onde o acoplamento se dá com atraso grande. São obtidas condições analíticas para ambos, a saber, sincronização de soluções periódicas e equilíbrios estáveis e controle de equilíbrio instáveis. Com um modelo de rede que inclui atraso com auto-alimentação, mostra-se a existência de um parâmetro crítico de acoplamento, kc, que depende apenas da estrutura da rede, do campo de vetores e da função de acoplamento, tal que para atraso grande e parâmetro de acoplamento k < kc a rede apresenta uma sincronização estável. Além disso, mostra-se que para redes heterogêneas, kc $\rightarrow$ 0 ao passo que o número de nós da rede cresce ao infinito, a menos que o parâmetro de acoplamento é escalonado com o grau máximo da rede. Em contrapartida, evidencia-se que para redes aleatórias, o intervalo de parâmetros de acoplamento que induzem sincronização estável é o máximo possível quando o limiar de conectividade da rede é atingindo fazendo com que a mesma se torne conectada. Baseando-se na estrutura da rede, propriedades de escalonamento do parâmetro de acoplamento são derivadas, permitindo sincronização estável. E, com um modelo de rede consistindo de auto-alimentação instantânea, verifica-se que é possível estabilizar soluções de equilíbrio que são instáveis no sistema isolado. Este cenário de controle quando o sistema isolado está próximo da bifurcação de Hopf é estudado em detalhes e então condições analíticas para a estabilidade são obtidas. Em particular, demonstra-se que os domínios de estabilização no espaço de parâmetros são periódicos e decrescentes ao passo que o atraso cresce. Além disso, evidencia-se como a frequência de reaparecimento de tais domínios é influenciada pelo número de raízes espectrais da matriz de adjacência do grafo, que por sua vez está relacionado com, por exemplo, as multipartições cíclicas do grafo.
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Guo, Hao. "Time synchronization and communication network redundancy for power network automation". Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/time-synchronization-and-communication-network-redundancy-for-power-network-automation(4d12b703-b970-4b8e-8335-b1d0b44112b6).html.
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Protection and Control (P&C) devices requiring accurate timing within a power transmission substation are commonly synchronized by distributed Global Positioning System (GPS) receivers. However, utilities now request a timing system that is less dependent on the direct use of distributed GPS receivers, because of the reliability issue of GPS receivers. In addition, to reduce device-to-device cabling and enable interoperability among devices from multiple vendors, utilities are looking to adopt the Ethernet based IEC 61850 protocol suites to complement or replace a conventional hardwired secondary P&C system. The IEEE 1588-2008 synchronization protocol is a network based time synchronization technique which can co-exist with the IEC 61850 applications and deliver sub-microsecond timing accuracy. A number of IEC 61850 applications require seamless communication redundancy, whilst existing technologies used in a substation only recover communications tens of milliseconds after a communication failure. Alternatively, the newly released IEC 62439-3 Parallel Redundancy Protocol (PRP) and High-availability Seamless Redundancy (HSR) can achieve seamless redundancy by transmitting duplicate data packets simultaneously in various networks and this can satisfy the extremely high reliability requirements of transmission substations. Considering the benefits, a unified network integrating IEEE 1588 and IEC 62439 PRP/HSR can be foreseen in future substations, but utilities need confidence in these technologies before real deployment. Hence, it is necessary to conduct comprehensive tests on such a timing system so that better insight into the performance and limitation can be obtained. This thesis first investigates the feasibility to integrate IEEE 1588 and IEC 62439 PRP into a single Ethernet network using a simulation tool and subsequently presents how the hardware testbed is established. Meanwhile, although GPS receivers are commonly used for time synchronization in the power industry, their performance might not be fully investigated before deployment. Hence, this thesis also proposes a procedure to assess the performance in terms of long term stability and transient behaviour of a timing system merely based on GPS receivers and one based on a mixture of GPS receivers and IEEE 1588 devices. Test results indicate whichever system is used, careful design of equipment, proper installation and appropriate engineering are required to satisfy the stringent accuracy requirements for critical automation applications in power system.
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Goes, Granville Manvel. "Advanced Ethernet Clock Synchronization based on Round Trip Time Protocol". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-276780.
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In this master thesis project, a new protocol called the Round Trip Time (RTT) protocol is implemented and verified. It helps determine the Ethernet clock frequency offset between two communicating nodes. The detection of this offset between nodes is a way to reduce the clock synchronization error. Ethernet is the basis on which a large amount of communication takes place in the world. Either it is used for exchanging data from one device to another or to connect devices to the internet. Due to the absence of clocks being exchanged between the various Ethernet communicating nodes, clock phase and frequency offsets can be present which leads to clock de-synchronization between the various nodes and results in lower system throughput. In the telecommunication industry, synchronization error between base stations can lead to lower throughput, performance degradation and packet loss. Also, with the introduction of 5G, stringent requirements will be placed on the clock synchronization errors.Currently, the Precision Time Protocol (PTP) is used to detect and correct clock synchronization errors. The PTP implementation reduces the clock synchronization error but it is still quite large. Hence, it is necessary to find a protocol which can work together with the PTP protocol to reduce this error. This thesis will introduce a new way to determine the clock frequency offset between nodes through the implementation of the RTT protocol. Through the course of this project, the clock frequency offset was determined by the RTT protocol. By comparing the expected and the theoretical clock offsets, it was concluded that the two values were very similar. The error between the offsets was in the range of 2.349-15.687 parts per billion (ppb) of the link frequency. Thus, the RTT protocol accurately and precisely determined the clock frequency offset between two Ethernet communicating nodes. This protocol is also extended to determine the clock frequency offset between two nodes transmitting periodic signals. For future works, this protocol can be combined with the PTP protocol and a way to determine the clock phase offset will be investigated.I detta examensarbete implementerades och verifierades ett nytt protokoll, kallat Round Trip Time (RTT)-protokollet, som hjälper till att bestämma Ethernets klockfrekvensförskjutning mellan två kommunicerande noder. Denna fastställda förskjutning mellan de två noderna är ett sätt att reducera klocksynkroniseringsfelet. Ethernet är grunden i en stor del av dagens kommunikation i världen. Antingen används det för informationsutbyte mellan två enheter, eller för att ansluta till internet. Då det saknas ett utbyte av referensklocka mellan de olika kommunikationsnoderna på Ethernet, kan det uppstå klockfasoch frekvensförskjutning som leder till att klockan desynkroniseras mellan de olika noderna och därmed ger ett minskat dataflöde. I telekommunikationsindustrin kan ett synkronisationsfel mellan basstationer leda till minskat dataflöde, sämre prestanda och paketförlust. I och med introduktionen av 5G kommer stränga krav att ställas på klocksynkronisationsfelen.För närvarande används Precision Time Protocol (PTP) för att upptäcka och korrigera klocksynkroniseringsfelen. Implementationen av PTP reducerar klocksynkroniseringsfelet, men det är fortfarande relativt stort. Därav är det nödvändigt att hitta ett protokoll som kan arbeta tillsammans med PTP för att reducera detta fel. Detta arbete kommer att introducera ett nytt sätt att bestämma klockfrekvensförskjutningen genom implementation av RTT-protokollet. I detta arbete bestämdes klockfrekvensförskjutningen av RTT-protokollet. Genom att jämföra det förväntade och faktiska värdet på klockförskjutningen kunde slutsatsen dras att de två värdena var väldigt lika. Felet var i storleksordningen av 2,349-15,687 parts per billion (ppb) i linkfrekvensen. Således bestämmer RTT-protokollet korrekt och exakt klockfrekvensförskjutningen mellan de två kommunikationsnoderna i Ethernet. Protokollet utökas också för att bestämma klockfrekvensförskjutningen mellan två noder som sänder en periodisk signal. För framtida arbete kan detta protokoll kombineras med PTP-protokollet, och det ska även undersökas ett sätt för att bestämma klockfasförskjutningen.
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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.
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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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Thungtong, Anurak. "Synchronization, Variability, and Nonlinearity Analysis: Applications to Physiological Time Series". Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1364316597.
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Lee, Hou-Hsun y 李厚勳. "Time Synchronization in Heterogeneous Networks". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/47644903248785319389.
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碩士國立臺灣大學
電信工程學研究所
100
In addition to theoretical study in statistical physics, synchronization in large heterogeneous networks has always been a technology challenge, due to lacking of common infrastructure and interface. However, mis-alignment of timing can significantly degrade the performance. In light of existing algorithms failing to effectively respond to node failure in timing, we develop an improved time synchronization algorithm enabling reliable synchronization in heterogeneous wireless networks. We discuss the performance of our algorithm on different network topologies and network size in order to understand the behavior of our algorithm, and further propose an enhanced algorithm that can be used on specific network topology. We also compare our algorithm with another binary-state consensus algorithm, the results turn out that our algorithm has many advantages. At last, we give two realistic network applications that can be well handled by our algorithm. We apply this improved algorithm to femtocells in LTE-A systems to successfully confine the timing errors in a more effective way, and this algorithm also decreases the influence of rumor spreader in social networks.
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Cox, Russ y William Josephson. "File Synchronization with Vector Time Pairs". 2005. http://hdl.handle.net/1721.1/30527.
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Vector time pairs are a new method for trackingsynchronization metadata. A vector time pairconsists of two vector times: one tracking filemodification history and one tracking filesynchronization history. Because the vectortimes are maintained separately and used fordifferent purposes, different algorithms andoptimizations can be applied to each. As aresult, vector time pairs impose no restrictionon synchronization patterns, never falsely detectconflicts, require no space to store deletionnotices, require network bandwidth proportionalonly to the number of files changed, and supportpartial synchronizations. No other currentsynchronization method has all these properties.Results from an implementation of vector timepairs in a new user-level file synchronizercalled Tra confirm the benefits of vectortime pairs.
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Tseng, Ming-Fong y 曾明鋒. "Feedforward Adaptive Sampling Time Synchronization Technique". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/44464784177068845038.
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碩士中華大學
電機工程學系碩士班
95
This thesis concentrates on the sampling time offset (STO) estimation scheme that employs the correlation of the short symbols specified in the preamble field of 802.11a WLAN frame structure. A simple detection strategy that uses four values and two values of the correlation is introduced. We also present a new algorithm by which the STO can be adaptively adjusted symbol by symbol. The adaptive algorithm inherits robustness against the variation of roll off rate and can improve the magnitude of the desired four points of correlated sequence. To take advantage of the adaptive algorithm, a linear curve fitting that focuses on the vicinity of zero STO is proposed, and then a state space based on the linear curve fitting can be constructed for a smoothing Kalman filter. Additionally, a threshold that can improve the STO detection is proposed to cooperate with the filter. The mean of estimation error resulted from this new scheme has been simulated for AWGN channels and multipath environments. Performance characteristics of the STO estimation using the non-adaptive method and the adaptive mode are evaluated via numerical examples. Our results show that the proposed method can effectively reduce STO.
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Vilares, Paulo Fernando Pereira. "Adaptive Time Synchronization Protocol for BANS". Master's thesis, 2012. https://repositorio-aberto.up.pt/handle/10216/66543.
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