共查询到20条相似文献,搜索用时 46 毫秒
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针对传统基于测距信息来设定上行同步方法中出现的频繁更新距离信息的问题,提出了基于位置信息的上行时钟同步方法。首先,通过测量伪距组成非线性方程组,采用基于最小二乘原理的解算方法定位出地面单元的位置信息;然后,由于卫星运动的位置信息已知,进一步可以得到星地间距离随时间的变化关系,距离换算成时延,即可得地面单元的上行信号发送时间提前量;最后,调整地面单元的发射机使上行信号以较高精度恰好在分配的时隙到达卫星,实现系统上行时钟同步的目的。仿真结果表明,所提方法能对全球范围内地面静止单元以较高精度实现卫星星座通信系统内上行时钟同步,避免频繁的测距更新,且精度更高。 相似文献
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介绍了基于NiosⅡ嵌入式软核处理器的工业以太网设备间精确时钟同步的设计与实现.利用Altera公司的Nios Ⅱ处理器,添加片内外设和存储器以及与片外存储器和外设相连的接口,通过SOPC(可编程片上系统)技术嵌入到FPGA芯片中形成Nios Ⅱ处理器系统硬件平台;软件部分移植uC/OS-Ⅱ作为操作系统,Lwip(轻量级TCP/IP协议)处理网络协议,在应用层上实现状态转换、同步报文处理和精确时钟算法.测试结果表明时钟同步精度高,并且最终在一个工业以太网实验平台上进行了长期的实际运行,系统稳定性良好. 相似文献
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《单片机与嵌入式系统应用》2009,(2):86-86
Silicon Laboratories(芯科实验室有限公司)发布抖动衰减时钟倍频芯片Si5315,进一步扩充任意速率(anyrate)精密时钟系列产品。新器件可满足甚至超出1G和10G同步以太网(SyncE)市场对于性能、集成度、频率和抖动的需求。除支持SONET/SDH和以太网时钟外,Si5315更可支持10G线路编码率(line encoding rates)(161.13MHz)。 相似文献
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时间触发以太网时钟同步的容错方法分析 总被引:1,自引:0,他引:1
为揭示高完整性和标准完整性配置下时钟同步容错方法的有效性,对时间触发以太网(time-triggered Ethernet,TTE)网络标准中时钟同步服务描述进行协议分析,还原时钟同步算法的理论模型。通过分析容错机制对应的失效模式,对TTE网络时钟同步算法在单同步域下对抗失效的有效性进行仿真验证,仿真结果表明了高完整性配置下的TTE网络时钟具备对抗单点随意失效的能力。 相似文献
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异步环境中基于时钟精度差的时钟同步 总被引:4,自引:0,他引:4
在异步通信模型的基础上,提出了一个基于时钟精度差的时钟同步策略,并给出了一个完整的系统模型,研究的重点有3个方面:(1)在时钟同步过程中使用单向信息传输策略,可以有效地减少网络负载;(2)客户机使用本地节点的时间信息和来自于参考时钟的时间戳信息构造一个线性数学模型,并获得本地时钟与参考时钟的运行精度差;(3)根据本地节点计算出的时钟精度差,构造一个自适应的容错模型,能够保证当本地节点与参考节点的连接出现故障时,本地的时钟同步系统还能够正常工作。该文不仅给出了一个详细的数学模型,而且还在实际的Internet环境中进行了模拟试验,取得了满意的结论。 相似文献
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杨福宇 《单片机与嵌入式系统应用》2011,11(4):3-6
介绍了FlexRay时钟同步的方法,发现由于延迟补偿不足或过头以及算法临界稳定特征根的存在,虽然节点间的偏差可以消除,但是它们将同向漂移,与节点内host的时钟发生偏离.普通帧因通信时钟比host变慢而丢帧;host与通信时钟同向漂移时帧就绪推迟,也会造成消息丢帧,从而产生到达顺序的混乱,影响其确定性与可靠性. 相似文献
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拥有百万资产的大型公司和设计师之间并不能总是融洽相处,很容易以妥协、过度宣传或者利润过低而收场,这动态的场景就是创意和商业之间的挣扎。因此,在上世纪来,意大利的时尚品牌贝纳通(Benetton)设立了Fabrica—它自己位于威尼靳之外的研究中心和创意中心—在没有先例的情况下开始了创意之路上的新探索。 相似文献
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基于本地时钟自校正的无线传感器网络同步方法 总被引:2,自引:0,他引:2
通过分析TPSN同步协议和造成时钟偏差不确定性的各种因素,结合无线传感器网络低功耗的特点及其对时钟同步算法精度的要求,针对TPSN未对时钟频率漂移进行估计的问题,提出一种节点本地时钟自校正方法,并设计了平均时钟偏差指标对一个同步周期内时钟精度进行评价。对比实验结果表明本方法易于实现,在保证同步精度的同时可以延长同步周期,减少同步开销,节约了能耗。 相似文献
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Interval-based Clock Synchronization 总被引:4,自引:0,他引:4
In this paper, we develop and analyze a simple interval-based algorithm suitable for fault-tolerant external clock synchronization. Unlike usual internal synchronization approaches, our convergence function-based algorithm provides approximately synchronized clocks maintaining both precision and accuracy w.r.t. external time. This is accomplished by means of a time representation relying on intervals that capture external time, providing accuracy information encoded in interval lengths. The algorithm, which is generic w.r.t. the convergence function and relies on either instantaneous correction or continuous amortization for clock adjustment, is analyzed by utilizing a novel, interval-based framework for establishing worst-case precision and accuracy bounds subject to a fairly detailed system model. Apart from individual clock rate and transmission delay bounds, our system model incorporates non-standard features like clock granularity and broadcast latencies as well. Relying on a suitable notion of internal global time, our analysis unifies treatment of precision and accuracy, ending up in striking conceptual beauty and expressive power. 相似文献
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Wait-Free Clock Synchronization 总被引:1,自引:0,他引:1
Multiprocessor computer systems are becoming increasingly important as vehicles for solving computationally expensive problems.
Synchronization among the processors is achieved with a variety of clock configurations. A new notion of fault-tolerance for
clock synchronization algorithms is defined, tailored to the requirements and failure patterns of shared memory multiprocessors.
Algorithms in this class can tolerate any number of napping processors, where a napping processor can fail by repeatedly ceasing operation for an arbitrary time interval and then resume
operation without necessarily recognizing that a fault has occurred. These algorithms guarantee that, for some fixed k, once a processor P has been working correctly for at least k time, then as long as P continues to work correctly, (1) P does not adjust its clock, and (2) P's clock agrees with the clock of every other processor that has also been working correctly for at least k time. Because a working processor must synchronize in a fixed amount of time regardless of the actions of the other processors,
these algorithms are called wait-free. Another useful type of fault-tolerance is called self-stabilization: starting with an arbitrary state of the system, a self-stabilizing algorithm eventually reaches a point after which it correctly
performs its task.
Two wait-free clock synchronization algorithms are presented for a model with global clock pulses. The first one is self-stabilizing;
the second one is not but it converges more quickly than the first one. The self-stabilizing algorithm requires each processor's
communication register contents to be a part of the processor's state. This last requirement is proven necessary. A wait-free
clock synchronization algorithm is also presented for a model with local clock pulses. This algorithm is not self-stabilizing.
Received December 20, 1993; revised January 1995. 相似文献
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Provides a framework for understanding system timing and then describes how the computer clock system executes the timing specifications. He examines clock generation and the construction of clock-distribution networks, which are integral to any clock system. Examples from contemporary high-speed systems highlight several common methods of clock generation, distribution, and tuning. Tight control of system clock skew is stressed 相似文献