Topic
Clock synchronization
About: Clock synchronization is a research topic. Over the lifetime, 7786 publications have been published within this topic receiving 133324 citations.
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23 Apr 2001
TL;DR: A new service model for time synchronization is proposed that provides a much more natural expression of these techniques: explicit timestamp conversions, and the implementation and characterization of several synchronization methods that exemplify the design principles are described.
Abstract: Time synchronization is a critical piece of infrastructure for any distributed system. Distributed, wireless sensor networks make extensive use of synchronized time, but often have unique requirements in the scope, lifetime, and precision of the synchronization achieved, as well as the time and energy required to achieve it. Existing time synchronization methods need to be extended to meet these new needs. We outline the synchronization requirements of future sensor networks and present an implementation of our own lowpower synchronization scheme, post-facto synchronization. We also describe an experiment that characterizes its performance for creating short-lived and localized but highprecision synchronization using very little energy.
512 citations
19 Sep 2003
TL;DR: It is shown that the communication complexity and accuracy of multi-hop synchronization is a function of the construction and depth of the spanning tree; several spanning-tree construction algorithms are described.
Abstract: This paper presents lightweight tree-based synchronization (LTS) methods for sensor networks. First, a single-hop, pair-wise synchronization scheme is analyzed. This scheme requires the exchange of only three messages and has Gaussian error properties. The single-hop approach is extended to a centralized multi-hop synchronization method. Multi-hop synchronization consists of pair-wise synchronizations performed along the edges of a spanning tree. Multi-hop synchronization requires only n-1 pair-wise synchronizations for a network of n nodes. In addition, we show that the communication complexity and accuracy of multi-hop synchronization is a function of the construction and depth of the spanning tree; several spanning-tree construction algorithms are described. Further, the required refresh rate of multi-hop synchronization is shown as a function of clock drift and the accuracy of single-hop synchronization. Finally, a distributed multi-hop synchronization is presented where nodes keep track of their own clock drift and their synchronization accuracy. In this scheme, nodes initialize their own resynchronization as needed.
510 citations
TL;DR: The authors describe the architectural assumptions, fault hypothesis, and objectives for the TTP protocol, and discuss TTP characteristics and compare its performance with that of other protocols proposed for control applications.
Abstract: The Time-Triggered Protocol integrates such services as predictable message transmission, clock synchronization, membership, mode change, and blackout handling. It also supports replicated nodes and replicated communication channels. The authors describe their architectural assumptions, fault hypothesis, and objectives for the TTP protocol. After they elaborate on its rationale, they give a detailed protocol description. They also discuss TTP characteristics and compare its performance with that of other protocols proposed for control applications. >
509 citations
02 Feb 2002
TL;DR: An alternative approach is described, which is called a multiple clock domain (MCD) processor, in which the chip is divided into several clock domains, within which independent voltage and frequency scaling can be performed.
Abstract: As clock frequency increases and feature size decreases, clock distribution and wire delays present a growing challenge to the designers of singly-clocked, globally synchronous systems. We describe an alternative approach, which we call a multiple clock domain (MCD) processor, in which the chip is divided into several clock domains, within which independent voltage and frequency scaling can be performed. Boundaries between domains are chosen to exploit existing queues, thereby minimizing inter-domain synchronization costs. We propose four clock domains, corresponding to the front end , integer units, floating point units, and load-store units. We evaluate this design using a simulation infrastructure based on SimpleScalar and Wattch. In an attempt to quantify potential energy savings independent of any particular on-line control strategy, we use off-line analysis of traces from a single-speed run of each of our benchmark applications to identify profitable reconfiguration points for a subsequent dynamic scaling run. Using applications from the MediaBench, Olden, and SPEC2000 benchmark suites, we obtain an average energy-delay product improvement of 20% with MCD compared to a modest 3% savings from voltage scaling a single clock and voltage system.
508 citations
TL;DR: The diffusion-based protocol is presented, which is fully localized, and it is shown that, by imposing some constraints on the sensor network, global clock synchronization can be achieved in the presence of malicious nodes that exhibit Byzantine failures.
Abstract: Global synchronization is important for many sensor network applications that require precise mapping of collected sensor data with the time of the events, for example, in tracking and surveillance. It also plays an important role in energy conservation in MAC layer protocols. This paper describes four methods to achieve global synchronization in a sensor network: a node-based approach, a hierarchical cluster-based method, a diffusion-based method, and a fault-tolerant diffusion-based method. The diffusion-based protocol is fully localized. We present two implementations of the diffusion-based protocol for synchronous and asynchronous systems and prove its convergence. Finally, we show that, by imposing some constraints on the sensor network, global clock synchronization can be achieved in the presence of malicious nodes that exhibit Byzantine failures.
504 citations