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Fine-grained network time synchronization using reference broadcasts
, 2002
"... Permission is granted for noncommercial reproduction of the work for educational or research purposes. ..."
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Cited by 764 (28 self)
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Permission is granted for noncommercial reproduction of the work for educational or research purposes.
Internet time synchronization: The network time protocol
, 1989
"... This memo describes the Network Time Protocol (NTP) designed to distribute time information in a large, diverse internet system operating at speeds from mundane to lightwave. It uses a returnabletime architecture in which a distributed subnet of time servers operating in a self-organizing, hierarchi ..."
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Cited by 617 (15 self)
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This memo describes the Network Time Protocol (NTP) designed to distribute time information in a large, diverse internet system operating at speeds from mundane to lightwave. It uses a returnabletime architecture in which a distributed subnet of time servers operating in a self-organizing, hierarchical, master-slave configuration synchronizes local clocks within the subnet and to national time standards via wire or radio. The servers can also redistribute time information within a network via local routing algorithms and time daemons. The architectures, algorithms and protocols which have evolved to NTP over several years of implementation and refinement are described in this paper. The synchronization subnet which has been in regular operation in the Internet for the last several years is described along with performance data which shows that timekeeping accuracy throughout most portions of the Internet can be ordinarily maintained to within a few tens of milliseconds, even in cases of failure or disruption of clocks, time servers or networks. This memo describes the Network Time Protocol, which is specified as an Internet Standard in
Simple, Accurate Time Synchronization for Wireless Sensor Networks
, 2003
"... Time synchronization is important for any distributed system. In particular, wireless sensor networks make extensive use of synchronized time in many contexts (e.g. for data fusion, TDMA schedules, synchronized sleep periods, etc.). Existing time synchronization methods were not designed with wirele ..."
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Cited by 142 (1 self)
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Time synchronization is important for any distributed system. In particular, wireless sensor networks make extensive use of synchronized time in many contexts (e.g. for data fusion, TDMA schedules, synchronized sleep periods, etc.). Existing time synchronization methods were not designed with wireless sensor networks in mind, and need to be extended or redesigned. Our solution centers around the development of a deterministic time synchronization method relevant for wireless sensor networks. The proposed solution features minimal complexity in network bandwidth, storage and processing and can achieve good accuracy. Highly relevant for sensor networks, it also provides tight, deterministic bounds on both the offsets and clock drifts. A method to synchronize the entire network in preparation for data fusion is presented. A real implementation of a wireless ad-hoc network is used to evaluate the performance of the proposed approach.
Dynamic Fault-Tolerant Clock Synchronization
, 1996
"... This paper gives two simple efficient distributed algorithms: one for keeping clocks in a network synchronized and one for allowing new processors to join the network with their clocks synchronized. Assuming a fault tolerant authentication protocol, the algorithms tolerate both link and processor fa ..."
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Cited by 141 (11 self)
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This paper gives two simple efficient distributed algorithms: one for keeping clocks in a network synchronized and one for allowing new processors to join the network with their clocks synchronized. Assuming a fault tolerant authentication protocol, the algorithms tolerate both link and processor failures of any type. The algorithm for maintaining synchronization works for arbitrary networks (rather than just completely connected networks) and tolerates any number of processor or communication link faults as long as the correct processors remain connected by fault-free paths. It thus represents an improvement over other clock synchronization algorithms such as [LM,WL], although, unlike them, it does require an authentication protocol to handle Byzantine faults. Our algorithm for allowing new processors to join requires that more than half the processors be correct, a requirement that is provably necessary. 1 Introduction In a distributed system it is often necessary for processors to ...
THe MAFT Architecture for distributed fault tolerance
- IEEE Transactions on Computers
, 1988
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Understanding Protocols for Byzantine Clock Synchronization
, 1987
"... All published fault-tolerant clock synchronization protocols are shown to result from refining a single paradigm. This allows the differera clock synchronization protocols to be compared and permits presemation of a single correctness analysis that holds for all. The paradigm is based on a reliab ..."
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Cited by 80 (0 self)
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All published fault-tolerant clock synchronization protocols are shown to result from refining a single paradigm. This allows the differera clock synchronization protocols to be compared and permits presemation of a single correctness analysis that holds for all. The paradigm is based on a reliable time source that periodically causes events; detection of such an event causes a processor to reset its clock. In a distributed system, the reliable time source can be approximated by combining the values of processor clocks using a generalization of a "fault-tolerant average", called a convergence function. The performance of a clock synchronization protocol based on our paradigm can be quantified in terms of the two parameters that characterize the behavior of the convergence function used: accuracy and precision.
Energy-aware TDMA-based MAC for sensor networks
- IEEE Workshop on Integrated Management of Power Aware Communications, Computing and Networking (IMPACCT 2002
, 2002
"... Networking unattended sensors is expected to have a significant impact on the efficiency of many military and civil applications. Sensors in such systems are typically disposable and expected to last until their energy drains. Therefore, energy is a very scarce resource for such sensor systems and h ..."
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Cited by 76 (6 self)
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Networking unattended sensors is expected to have a significant impact on the efficiency of many military and civil applications. Sensors in such systems are typically disposable and expected to last until their energy drains. Therefore, energy is a very scarce resource for such sensor systems and has to be managed wisely in order to extend the life of the sensors for the duration of a particular mission. In this paper, we present a novel approach for energyaware management of sensor networks that maximizes the lifetime of the sensors while maintaining desired quality of service attributes related to sensed data delivery. The approach is to dynamically set routes and arbitrate medium access to minimize energy consumption and maximize sensor life. We give a brief overview of the energyaware routing and describe a Time-Division-Multiple-Access (TDMA)-based Medium Access Control (MAC) protocol. We discuss algorithms for assigning time slots for the communicating sensor nodes. The approach is evaluated through simulation. Simulation results have confirmed the effectiveness of our new approach. 1.
RealTime Computing: A New Discipline of Computer Science and Engineering
- Proceedings of IEEE, Special Issue on Real-Time Systems
, 1994
"... This paper surveys the state of the art in real-time computing. It introduces basic concepts and identifies key issues in the design of real-time systems. Solutions proposed in literature for tackling these issues are also briejy discussed. I. ..."
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Cited by 62 (5 self)
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This paper surveys the state of the art in real-time computing. It introduces basic concepts and identifies key issues in the design of real-time systems. Solutions proposed in literature for tackling these issues are also briejy discussed. I.
Self-Stabilizing Clock Synchronization in the presence of Byzantine faults
- Journal of the ACM
, 1995
"... We initiate a study of bounded clock synchronization under a more severe fault model than that proposed by Lamport and Melliar-Smith [LM-85]. Realistic aspects of the problem of synchronizing clocks in the presence of faults are considered. One aspect is that clock synchronization is an on-going tas ..."
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Cited by 58 (11 self)
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We initiate a study of bounded clock synchronization under a more severe fault model than that proposed by Lamport and Melliar-Smith [LM-85]. Realistic aspects of the problem of synchronizing clocks in the presence of faults are considered. One aspect is that clock synchronization is an on-going task, thus the assumption that in any period of the execution at least two thirds of the processors are nonfaulty is too optimistic. To cope with this reality we suggest self-stabilizing protocols that stabilize in any (long enough) period in which less than a third of the processors are faulty. Another aspect is that the clock value is bounded. A single transient fault may cause the clock to reach the upper bound. Therefore we suggest a bounded clock that wraps around when appropriate. We present two randomized self-stabilizing protocols for synchronizing bounded clocks in the presence of Byzantine processor failures. The rst protocol assumes that processors have a common pulse, while the second protocol does not. A new type of distributed counter based on the Chinese remainder theorem is used as part of the rst protocol. 1
