共查询到19条相似文献,搜索用时 109 毫秒
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随着计算机网络技术和分布式理论的发展,在异步环境中的时间同步问题就显得越来越重要。提出了一种基于时钟精度差的时间同步策略,并给出了相应的证明,同时也讨论了一种基于连续时间变化的领导选择策略,以保证获得正确的标准时钟基。 相似文献
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为推进并行离散事件仿真技术在复杂制造仿真系统中的应用,提高仿真效率,针对制造系统仿真模型,研究和实现了一种基于时间窗的受限滞后保守同步策略。阐明了策略的思想,具体分析了策略中距离矩阵、关联矩阵、时钟推进等关键要素,给出了策略的实现流程。实践表明了该同步策略具有建模容易,仿真效率高的特点,为仿真模拟复杂制造系统提供了较好的同步机制。 相似文献
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IEEE1588协议硬件时间戳标记电路设计 总被引:1,自引:0,他引:1
IEEE1588协议是一种基于网络多播技术的精密时钟同步协议,为了提高时钟同步的精度,提出了一种在以太网物理层和MAC层之间的介质无关接口(MII/RMII)处检测同步报文的策略和实现精确时间戳标记方案,在此方案基础上设计和实现了基于FP-GA的硬件时间戳标记电路;设计了相关测试平台,对设计电路进行了测试和验证,测试结果表明设计的时间戳标记电路可以在RMII接口处实时地标记同步报文的收发时间戳,设计达到课题要求,应用性能良好。 相似文献
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在提供IP电话服务时,时延抖动是一个重要的QoS参数。提出的一种去抖动同步策略综合考虑了如何能达到消除延时抖动的影响,同时又能保证良好的播放实时性。该策略将基于播放时间的同步去抖算法和基于接收缓存数据量控制的再同步算法有机结合并改进,从中获得最佳同步调整,同时还实现了对网络状况的自适应估计。实验证明接收方使用该综合去抖动同步策略能保证接收端语音流平稳连续播放,能使得IP电话的QoS得到很大改善。 相似文献
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基于最优线性拟合的WSN时间同步算法研究 总被引:1,自引:0,他引:1
针对传感器网络应用对节点同步精度要求高、通信开销小等需求,研究一种基于最优线性拟合的时间同步算法。在分析FTSP算法的基础上,通过节点分级策略,减少同步分组数据传输量,并引入概率统计学中参数估计理论改进线性回归算法,减小异常数据点对同步精度的影响,延长节点同步时间。实验结果表明:该算法能有效减少同步通信开销,实现高精度的时间同步,同步误差在μs级。 相似文献
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Daniela Tulone 《Algorithmica》2007,49(4):386-411
We study the problem of providing a sensor with an accurate estimate of the time, from a novel perspective which is complementary to the well-studied clock synchronization problem. More precisely, we analyze the case in which a
sensor node is temporarily unable to run a clock synchronization protocol due to failures or intermittent connectivity, or
is willing to skip one or more clock adjustments to save energy, but still requires an accurate estimate of the reference time.
We propose and analyze two simple and efficient clock reading methods, one deterministic and the other probabilistic, which
are designed to work in synergy with a clock synchronization protocol. Our deterministic method achieves a better time accuracy
by exploiting information regarding the sign of the deviation of the hardware clock from the reference time. This algorithm
leads to noticeable energy savings since it can be applied to reduce the frequency of the periodic clock adjustments by a
factor of 2, while maintaining the same error bound. Moreover, our method is of theoretical interest since it shows how a
stronger but realistic clock model leads to a refinement of the optimality bound for the maximum deviation of a clock that is periodically synchronized. We also propose two simple versions of this algorithm:
a method that guarantees the monotonicity of the clock values, and a generalization that improves the accuracy in case of
clock stability.
Our probabilistic method is based on time series forecasting, and provides a probabilistically accurate estimate of the reference time with a constant error bound. It is more flexible
than our previous methods since it does not depend on the frequency at which clock synchronization occurs, and can be dynamically
tuned according to the application requirements and resource availability. All these methods have broad applicability for
their generality. In sensor networks they can be applied to improve the clock accuracy of a sensor node in conditions of network
isolation, or to reduce the frequency of the clock adjustments, thus saving energy and increasing the system lifetime. 相似文献
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在网络化分布式测试与控制系统中,时钟同步是一项重要的课题研究指标.在基于IEEE 1588协议主从时钟的时钟同步中,时钟偏差和时钟漂移的精确测量是主从时钟同步的重要保证.提出了基于卡尔曼滤波的时钟同步方法,该方法不仅能对主从节点之间的时钟漂移进行估计、优化时钟模型,还能实现对时钟偏差的估计,消除传输网络中的干扰.实验结果表明,在时钟同步中引入卡尔曼滤波算法能显著提高时钟同步精度. 相似文献
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随首航空发动机控制技术的发展,全权限数字电子控制(FADEC)系统的可靠性设计变得越来越重要;在FADEC系统中,同步设计对于提高航空发动机全权限数字式电子控制器的可靠性具有重要的意义;为了解决如何在FADEC系统中实现双机时钟缓同步设计,简要的分析了应注意的问题;随限介绍了设计中采取软硬件相结合来同步两计算机实时时钟的基本方法,在实践中证明了该方法是行之有效的。 相似文献
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无线传感器在网络应用中要求节点间保持时间同步,但现存的经典时间同步算法,因节点的接收时间受时钟偏差和传输延迟的影响,其同步精度不高。为提高网络时间同步精度,均衡节点能耗,提出了一种改进的层次参考时间同步算法(Improved Hierarchy Referencing Time Synchronization,IHRTS)。该算法基于节点在层次结构中唯一物理位置的时间特性,采用贝叶斯估计对节点接收时间进行估算,缩小时间偏差的误差范围,获得比较精确的同步偏移量,从而改善时间同步精度;同时采用无线信道的广播特性与双向同步机制的同步思想,最小化了通信负载,均衡了节点能耗。通过仿真结果表明将贝叶斯估计方法应用到时间同步算法中,在均衡节点能量消耗同时有效地提高了网络同步精度。 相似文献
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Integrating External and Internal Clock Synchronization 总被引:2,自引:1,他引:1
We address the problem of how to integrate fault-tolerant external and internal clock synchronization. In this paper we propose a new external/internal clock synchronization algorithm which provides both external and internal clock synchronization for as long as a majority of the reference time servers (servers with access to reference time) stay correct. When half or more of the reference time servers are faulty, the algorithm degrades to a fault-tolerant internal clock synchronization algorithm. We prove that at least 2 F+1 reference time servers are necessary for achieving external clock synchronization when up to F reference time servers can suffer arbitrary failures, thus the proposed algorithm provides maximum fault-tolerance. In this paper we also derive lower bounds for the best maximum external deviation achievable in standard mode and the best drift rate achievable in degraded mode. Our algorithm is optimal with respect to these two bounds: (1) the maximum external deviation is optimal in standard mode, and (2) the drift rate of the clocks is optimal in standard and degraded mode. 相似文献
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This paper presents an innovative method to synchronize physical clocks for a computational grid, in particular for a computational grid linked through the asynchronous In-tranet or Internet environments. The method discussed is an asynchronous self-adaptive clock synchronization mechanism. Two strategies for clock synchronisation are introduced. (1) Use con-tinuous time intervals to calculate the precision of clocks, which can reduce the effect of network delay effciently. (2) Every node synchronizes its clock with its leader actively. In addition, a node self-adaptive model is presented, and the relationship between the clock precision and synchroniza-tion time is induced, hence a node can predict when it should begin the synchronization process.Detailed simulation and extension of this issue are provided at the end of the paper. The presented model is both practical and feasible. 相似文献