Download or read book Implementation Issues in Clock Synchronization written by Micah Beck and published by . This book was released on 1986 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present some results from an experimental implementation of a recent clocks synchronization algorithm. This algorithm was designed to overcome arbitrary processor failures, and to achieve optimal accuracy, i.e., the accuracy of synchronized clocks (with respect to real time) is as good as that specified for the underlying hardware clocks. Our system was implemented on a set of workstations on a local area braodcast network. Initial results indicate that this algorithm can form the basis of an accurate, reliable, and practical distributed time service.

Download or read book Wireless Networks Model and Optimization Based Approaches to Clock Synchronization Random Access MAC and Video Streaming written by Nikolaos M. Freris and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We, via a model and optimization-based approach, address three issues related to wireless networks: clock synchronization, medium access control (MAC) and scalable video streaming. In Chapter 2 we develop, study and simulate a new model-based distributed network clock synchronization protocol. In a network of clocks, a given node is taken as reference and is associated with the time evolution t. We introduce and analyze a stochastic model for clocks, in which the relative speedup of a clock with respect to the reference node, called the skew, is characterized by an exponential transformation of an Orstein-Uhlenbeck process. We study the properties of our model, namely moment and sample path properties of the stochastic processes, and calculate its Allan variance. We show how our model can be used to translate the time of a clock to another clock's units. We study the problem of synchronizing clocks in a network, which amounts to estimating the instantaneous relative skews and relative offsets, i.e., the differences in the clock readouts, by exchange of time-stamped packets between pairs of nodes in the network. Based on a stochastic model for delays, we derive a scheme for obtaining relative skew measurements in a communication link by sending two time-stamped packets from node i to node j in order to obtain a noisy measurement of their relative skew. We develop an algorithm for filtering relative skew measurements across a link (i,j) in order to estimate the logarithm of the relative skew. We study the properties of the algorithms and provide theoretical guarantees on their performance. We also develop an online, centralized, model-based, asynchronous skew estimation algorithm for optimal filtering of the time-stamps in the entire network, as well as an efficient distributed suboptimal scheme which demonstrates near-optimal performance in simulations. Furthermore, we study some implementation issues, and present a scheme for pairwise relative offset estimation given skew estimates. We use the distributed asynchronous algorithm to obtain nodal offset estimates from relative offset estimates. We combine our findings into developing a new protocol for clock synchronization, namely the Model-Based Clock Synchronization Protocol (MBCSP). We present a comparative simulation study of its performance versus the leading scheme by Solis et al. (2006); the results show that MBCSP performs better in terms of skew, offset and delay estimation. Finally, we have performed trace-driven simulation based on time-stamps obtained from Berkeley motes. Our scheme outperforms that of Solis et al. by 45%, where we used the accuracy in predicting the receipt time-stamp at the sender as the clock synchronization metric. In Chapter 3, we study random access based MAC in the framework of network utility maximization (NUM). There has been much recent interest in protocol design for wireless networks based on maximizing a network utility function. A significant advance is the observation that a decomposition of the Lagrangian suggests an approach where transmissions are scheduled to minimize back-pressure. However, a satisfactory MAC protocol that can realize such a scheduling algorithm is notably missing, and we develop one potential scheme. We present a candidate random access MAC protocol that extends an existing algorithm by Gupta and Stolyar (2006) in calculating the access probabilities. We also consider the online adaptation of access probabilities using local information about queue lengths and active links. We provide OPNET simulation results to compare the performance of our scheme with the leading schemes. We estimate the capacity region of our scheme by simulation for various topologies and multiple flows. Our simulation studies indicate that our extension in conjunction with an implementation of back-pressure significantly outperforms the slotted-time algorithm of Gupta and Stolyar (2006). In Chapter 4, we present performance bounds for random access based MAC using carrier-sense multiple access (CSMA). In recent work, it was shown that a distributed CSMA-based MAC protocol is throughput-optimal which, in turn, implies that the class of controlled distributed random access MAC protocols can support the entire capacity region. It is challenging to study the performance of such schemes in terms of mean delays and compare it with some known results on the performance of centralized scheduling. We modify the model of Jiang and Walrand (2008) to obtain Markov chain models that incorporate the queue lengths as well as the information about the independent set, for single-hop networks. We show that the delay of the new models yields an upper bound on the delay of the original models. We derive upper and lower bounds on the mean total delay at the steady-state, and show that these bounds coincide with those for max-weight scheduling. Finally, we develop a method of deriving upper and lower bounds for random-access schemes by using linear programs (LPs). We present an optimization program for minimizing the upper bounds. In Chapter 5, we consider multihomed scalable video streaming systems where each video is concurrently transmitted over several access networks to a client. The problem is to determine which video packets of a video stream to transmit, and associate each video packet with an access network, so that the video quality at the client is maximized under measured network conditions. We present a network model and a video distortion model to capture the network conditions and video distortion characteristics, respectively. We develop a mathematical formulation to find the streaming strategy for maximizing the average video quality at the client. While the formulation can be optimally solved using exhaustive search or dynamic programming, doing so takes a prohibitively long time, and is not practical for real-time video streaming servers. In order to efficiently solve the problem in real time, we propose several suboptimal convex problems along with two heuristic algorithms. We conduct extensive trace-driven simulations to evaluate the algorithms using real network conditions and actual scalable video streams. We compare our algorithms against the rate control algorithms defined in the Datagram Congestion Control Protocol (DCCP) standard. The simulation results show that our algorithms significantly outperform current systems while being TCP-friendly. For example, compared to DCCP, our algorithms achieve at least 10 dB quality improvement and result in up to 83% packet delivery delay reduction. Finally, we study the trade-off between efficiency and optimality: One of the heuristic algorithms runs faster and is suitable for large-scale streaming systems, while the other one achieves better video quality and is more appropriate for smaller streaming servers. The convex programming approach demonstrates a good trade-off between running time and performance.

Download or read book Synchronization Techniques for Digital Receivers written by Umberto Mengali and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 532 pages. Available in PDF, EPUB and Kindle. Book excerpt: Synchronization is a critical function in digital communications; its failures may have catastrophic effects on the transmission system performance. Furthermore, synchronization circuits comprehend such a large part of the receiver hardware that their implementation has a substantial impact on the overall costs. For these reasons design engineers are particularly concerned with the development of new and more efficient synchronization structures. Unfortunately, the advent of digital VLSI technology has radically affected modem design rules, to a point that most analog techniques employed so far have become totally obsolete. Although digital synchronization methods are well established by now in the literature, they only appear in the form of technical papers, often concentrating on specific performance or implementation issues. As a consequence they are hardly useful to give a unified view of an otherwise seemingly heterogeneous field. It is widely recognized that a fundamental understanding of digital synchronization can only be reached by providing the designer with a solid theoretical framework, or else he will not know where to adjust his methods when he attempts to apply them to new situations. The task of the present book is just to develop such a framework.

Download or read book Synchronization of Digital Telecommunications Networks written by Stefano Bregni and published by John Wiley & Sons. This book was released on 2002 with total page 446 pages. Available in PDF, EPUB and Kindle. Book excerpt: Network synchronization deals with the distribution of time and frequency across a network of clocks often spread over a wide geographical area. The goal is to align (i.e. synchronize) the time and frequency scales of all clocks, by using the communication capacity of their interconnecting links. Network synchronization plays a central role in digital telecommunications as it determines the quality of most services offered by the network operator. However, the importance of network synchronization is often underestimated and how to solve quality-of-service degradation caused by synchronization difficulties can become problematical to all but a synchronization engineer. * Systematically covers a wide spectrum of both theoretical and practical topics * Features a clear and profound description of synchronous and asynchronous digital multiplexing (PDH, SDH), jitter and timing aspects of SDH networks * Expounds synchronization network principles and implementation issues, clock modelling, time and frequency measurement * Presents recent advances in telecommunications clock characterization and measurement If you are a system engineer, researcher, designer or postgraduate student searching for both the basics and an insight into more advanced areas currently under discussion then you will find Synchronization of Digital Telecommunications Networks an enlightening read. It will also prove to be a valuable sourcebook for senior undergraduates and technical personnel in telecommunications companies.

Download or read book DISTRIBUTED OPERATING SYSTEMS written by PRADEEP K. SINHA and published by PHI Learning Pvt. Ltd.. This book was released on 1998-01-01 with total page 761 pages. Available in PDF, EPUB and Kindle. Book excerpt: The highly praised book in communications networking from IEEE Press, now available in the Eastern Economy Edition.This is a non-mathematical introduction to Distributed Operating Systems explaining the fundamental concepts and design principles of this emerging technology. As a textbook for students and as a self-study text for systems managers and software engineers, this book provides a concise and an informal introduction to the subject.

Download or read book An Optimized Implementation of a Fault tolerant Clock Synchronization Circuit written by and published by . This book was released on 1995 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Optimized Implementation of a Fault Tolerant Clock Synchronization Circuit written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-30 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: A fault-tolerant clock synchronization circuit was designed and tested. A comparison to a previous design and the procedure followed to achieve the current optimization are included. The report also includes a description of the system and the results of tests performed to study the synchronization and fault-tolerant characteristics of the implementation. Torres-Pomales, Wilfredo Langley Research Center RTOP 505-64-10-13...

Download or read book A Hardware Implementation of a Provably Correct Design of a Fault tolerant Clock Synchronization Circuit written by and published by . This book was released on 1993 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Special Topics in Structural Dynamics Experimental Techniques Volume 5 written by David S. Epp and published by Springer Nature. This book was released on 2020-09-18 with total page 349 pages. Available in PDF, EPUB and Kindle. Book excerpt: Special Topics in Structural Dynamics & Experimental Techniques, Volume 5: Proceedings of the 38th MAC, A Conference and Exposition on Structural Dynamics, 2020, the fifth volume of eight from the Conference brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on fundamental and applied aspects of Structural Dynamics, including papers on: Analytical Methods Emerging Technologies for Structural Dynamics Engineering Extremes Experimental Techniques Finite Element Techniques General Topics

Download or read book Clock Synchronization in Distributed Systems written by Martin Horauer and published by Sudwestdeutscher Verlag Fur. This book was released on 2009 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: A system-wide global time base with known precision is frequently of pivotal importance for the design and operation of distributed systems and services. The requirements and the large scale often demand a high-precision below the microsecond-range. The IEEE-1588 standard addresses these issues and proposes ways for a suitable implementation. Complementing these solutions, an alternative architecture for network interfaces and networked devices is proposed that renders a worst-case precision in the 100 ns-range possible. Furthermore, an analysis and an experimental evaluation reveals actual values for the worst-case precision that might be achieved.

Download or read book Design and Implementation of Dynamic Threshold Algorithms for Clock Synchronization in a Heterogeneous Computer Network written by Faisal Masood Asif and published by . This book was released on 1993 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Euro Par 2002 Parallel Processing written by Burkhard Monien and published by Springer Science & Business Media. This book was released on 2002-08-21 with total page 1017 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the refereed proceedings of the 8th European Conference on Parallel Computing, Euro-Par 2002, held in Paderborn, Germany in August 2002. The 67 revised full papers and 55 research note papers presented together with 6 invited papers were carefully reviewed and selected from 265 submissions. The papers presented give a unique survey of the state of the art in parallel computing research, ranging from algorithms, software, hardware and application in various fields.

Download or read book Maintaining Synchronized Clocks in a Distributed Environment written by Eugene You-Nian Ding and published by . This book was released on 1987 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synchronous Ethernet and IEEE 1588 in Telecoms written by Jean-Loup Ferrant and published by John Wiley & Sons. This book was released on 2013-06-12 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses the multiple technical aspects of the distribution of synchronization in new generation telecommunication networks, focusing in particular on synchronous Ethernet and IEEE1588 technologies. Many packet network engineers struggle with understanding the challenges that precise synchronization distribution can impose on networks. The usual “why”, “when” and particularly “how” can cause problems for many engineers. In parallel to this, some other markets have identical synchronization requirements, but with their own design requirements, generating further questions. This book attempts to respond to the different questions by providing background technical information. Invaluable information on state of-the-art packet network synchronization and timing architectures is provided, as well as an unbiased view on the synchronization technologies that have been internationally standardized over recent years, with the aim of providing the average reader (who is not skilled in the art) with a better understanding of this topic. The book focuses specifically on synchronous Ethernet and IEEE 1588 PTP-based technologies, both key developments in the world of synchronization over the last 10 years. The authors address the needs of engineers and technical managers who are struggling with the subject of synchronization and provide an engineering reference for those that need to consider synchronization in NGN. The market applications that are driving the development of packet network synchronization and timing architectures are also discussed. This book provides a wide audience with everything they need to know when researching, implementing, buying and deploying packet synchronization architectures in telecommunication networks.

Download or read book EUC 2004 written by Laurence T. Yang and published by Springer Science & Business Media. This book was released on 2004-08-18 with total page 1135 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the refereed proceedings of the International Conference on Embedded and Ubiquitous Computing, EUC 2004, held in Aizu-Wakamatsu City, Japan, in August 2004. The 104 revised full papers presented were carefully reviewed and selected from more than 260 submissions. The papers are organized in topical sections on embedded hardware and software; real-time systems; power-aware computing; hardware/software codesign and systems-on-chip; mobile computing; wireless communication; multimedia and pervasive computing; agent technology and distributed computing, network protocols, security, and fault-tolerance; and middleware and peer-to-peer computing.

Download or read book Clock Synchronization and Comparison written by James E. Gray and published by . This book was released on 1976 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Survey of Provably Correct Fault Tolerant Clock Synchronization Techniques written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-29 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: Six provably correct fault-tolerant clock synchronization algorithms are examined. These algorithms are all presented in the same notation to permit easier comprehension and comparison. The advantages and disadvantages of the different techniques are examined and issues related to the implementation of these algorithms are discussed. The paper argues for the use of such algorithms in life-critical applications. Butler, Ricky W. Langley Research Center RTOP 505-66-21-01...