原子钟相位一时间起伏周期的小波分析

文中根据小波变换的奇异性检测原理，分析了环境温度变化对原子钟特性的影响。基于小波变换的信号重建原理，将温度变化引起原子钟相位-时间起伏进行时-频域分离。用小波变换理论分析了由于昼夜温度变化引起原子钟周期性波动的原因，结合传统的港分析方法，认证了原子钟相位－时间起伏的周期性。结果表明：在有环境温度调节的环境中，氢原子钟的相位－时间起伏标准差41ns左右，在一般环境中，她原子钟的相位一时间起伏标准差21us左右。改善环境条件可以提高原子钟的频率稳定度。     

Clocking Optimization and Distribution in Digital Systems with Scheduled Skews

System performance can be improved by employing scheduled skews at flip-flops. This optimization technique is called skewed-clock optimization and has been successfully used in memory designs to achieve high operating frequencies. There are two important issues in developing this optimization technique. The first is the selection of appropriate clock skews to improve system performance. The second is to reliably distribute skewed clocks in the presence of manufacturing and environmental variations. Without the careful selection of clocking times and control of unintentional clock skews, potential system performance might not be achieved. In this paper a theoretical framework is first presented for solving the problem of optimally scheduling skews. A novel self-calibrating clock distribution scheme is then developed which can automatically track variations and minimize unintentional skews. Clocks with proper skews can be reliably delivered by such a scheme.     

5G承载网产品低时延及高精度时钟的抗扰性

Wang Zhenying     

Stability Analysis of Periodic Orbits of Nonautonomous Piecewise-Linear Systems by Mapping Approach

In this brief, we present an exact stability analysis for periodic orbits of nonautonomous piecewise-linear systems. The described discrete-time maps are derived by connecting solutions at the switched points and solving relevant sets of linear differential equations. The coordinates of the switched points of the periodic orbit on each switching surface and the corresponding Jacobians are obtained. Theoretical analysis and simulation results for the piecewise-linear Duffing oscillator and Colpitts oscillator are presented to illustrate the proposed method.      

Replicated Object Management with Periodic Maintenance in Mobile Wireless Systems

In this paper we analyze periodic maintenance strategies for managing replicated objectsin mobile wireless environments. Under periodical maintenancestrategies, the system periodically checks local cells to determineif a replicated object should be allocated or deallocated in a cell to reduce the access cost.We develop a performance model based on Petri netsthat considers the missing-read cost, write-propagationcost and the periodic maintenance cost with the objective to identify optimal periodic maintenance intervals to minimize theoverall cost. The analysis results show that the overall cost is highwhen the user arrival-departure ratio andthe read-write ratio work against each other and is low otherwise. In all cases, there exists an optimal periodic maintenance interval that would yield the minimum cost.Further, the optimal periodic maintenance interval increases as the arrival-departure ratio andthe read-write ratio work in harmony.     

Design and Implementation of a Latency Efficient Encoder for LTE Systems

The operation time of an encoder is one of the critical implementation issues for satisfying the timing requirements of Long Term Evolution (LTE) systems because the encoder is based on binary operations. In this paper, we propose a design and implementation of a latency efficient encoder for LTE systems. By virtue of 8‐bit parallel processing of the cyclic redundancy checking attachment, code block (CB) segmentation, and a parallel processor, we are able to construct engines for turbo codings and rate matchings of each CB in a parallel fashion. Experimental results illustrate that although the total area and clock period of the proposed scheme are 19% and 6% larger than those of a conventional method based on a serial scheme, respectively, our parallel structure decreases the latency by about 32% to 65% compared with a serial structure. In particular, our approach is more latency efficient when the encoder processes a number of CBs. In addition, we apply the proposed scheme to a real system based on LTE, so that the timing requirement for ACK/NACK transmission is met by employing the encoder based on the parallel structure.     

优先级网络性能的网络演算分析

基于网络演算理论,对考虑信道差错过程影响的优先级网络系统性能进行了综合分析;基于网络演算推导出信道差错过程的随机到达曲线,在此基础上,获得不同优先级用户的随机服务曲线,进而分析相应的网络服务保证,即时延边界和存储空间边界。基于不同的业务到达模型,研究了不同系统配置下的时延边界,并对相应数值结果加以深入分析。     

几乎周期时变MA系统的辨识

本文利用循环统计量讨论几乎周期时变滑动平均（ＡＰＴＶ－ＭＡ）系统的辨识问题,提出了基于奇数阶时变累量的参数估计的法方程方法,并导出了基于时变累量和循环累量的系统模型定阶方法。仿真实验说明了本文所提方法的性能。     

LTE系统时延分析

介绍由eNodeB构成的单层结构的LTE系统对时延的要求,从用户面时延、控制面时延进行具体的理论分析,并通过举例进一步介绍LTE系统在inter—eNB切换中的业务中断时延。     

Reliability of Periodic, Coherent, Binary Systems

A new phased-mission analysis considers periodic systems without repair. Periodic systems arise in applications such as aviation where a sequence of operating phases is repeated during each flight. A theorem relates such systems to a traditional single-phase system. The single-phase system is useful for approximating the reliability and mean life of the periodic system and is much simpler to analyze than exact transformations to a single-phase system.     

EMI Tuning of Hybrid Systems by Periodic Patterns

Hybrid systems are known to be potential sources of electromagnetic interference due to their principle of recurrently switching voltages and currents. In this paper, we demonstrate different periodic modulation techniques and propose corresponding electromagnetic compatibility optimization methods. A systematic way to optimize finite length modulation sequences is proposed. We prepare mathematical expressions of performance indexes as a base for optimization algorithms. The performance of the different waveform generation methods is veryfied using a dc–dc converter example. It points out that the optimized waveforms are a powerful tool to shape the power spectrum.     

Energy Efficiency and Latency Analysis of Fog Networks

The industry of cellular networks is evaluating the new architectures to ensure an enhanced performance. Fog communication is the new paradigm that presented to unleash edge computing. In this paper, we introduced a mathematical framework to evaluate the trade-offs of Fog proposal. Specifically, testing the power consumption, delay and energy efficiency in comparison with traditional cloud radio access networks. Although the literature has showed that fog radio access networks provides an enhanced delay performance, this paper shows that an enlarged amount of power is consumed, which degrades the energy efficiency in comparison with traditional cloud counterpart. However, the level of such devolution depends on the number of deployed fog devices that directly influences the power consumption. This paper also shows that enhancing the delay by using fog architecture is not a straight forward process, but requires a particular caring in terms of choosing the appropriate mode while placing/installing fog functions within fog devices.     

Coded Error Probability for DS Spread-Spectrum Systems with Periodic Pulsed Multiple-Tone Interference

The coded error probability for direct sequence (DS) BPSK or QPSK spread-spectrum systems, used with or without interleaving, and operating in the presence of pulsed multiple-tone interference, is investigated. We consider the worst-case channel error probability under conditions of pulsed multiple-tone jamming for the various systems, and present coded error probability as a function of interleaving delay for(n, k)block codes with hard-decision decoding. It is shown that when the maximum level of continuous multiple-tone interference does not exceed the level of the desired signal, the duty cycle of the corresponding pulsed interference which yields the worst-case error probability is usually small, and that the smaller the duty factor of the jamming, the more considerable is the performance improvement due to the use of interleaving in conjunction with the coding.     

FPGA芯片时钟架构分析

FPGA设计中时钟信号的设计与处理是保证系统稳定工作的重要组成部分,随着FPGA器件规模的不断增大,集成度不断提高,多时钟域管理、时钟延迟、时钟信号完整性和相位偏移等已成为影响FPGA设计的关键因素。结合微电子电路相关知识,针对Xilinx公司的Virtex4系列芯片,详细分析其时钟架构及时钟资源的特性。针对FPGA时钟设计的典型应用情况,从芯片角度给出了时钟设计与使用的一些技巧和建议。     

浅析通信系统中的准确度与时钟发生器技术

数字时钟性能最重要的技术指标之一就是准确度,它通常以 PPM(×10-6)为标准来衡量。准确度在通信系统中至关重要,而不同的通信技术则要求其时钟源具备不同级别的准确度。计时系统的准确度不仅取决于时钟源晶体特性,而且还取决于从源参考生成频率的数字PLL 时钟发生器的配置与技术。目前可用的时钟发生器技术很多,可提供不同级别的准确度以满足几乎所有应用的需要。高效使用上述技术可实现更高的准确度,并减少所需的高准确度与精确晶体的数量。准确度 (Accuracy) 与精确度 (Precision)时钟准确度的定义为:时钟频率与理想时钟频率的吻合度…     

Bounds on MTBF of Systems Subjected to Periodic Maintenance

Mean time between failures (MTBF) is a common reliability measure used to assess the failure behavior of repairable systems. In order to increase MTBF, in most systems, it is a common practice to perform preventive maintenance activities at periodic intervals. In this paper: We first discuss the validity of a commonly used equation for computing MTBF of systems subjected to periodic maintenance. For complex systems where this equation is valid, we propose a simple and better approximation than the exponential approximation proposed in a recent paper. In addition, we prove that for systems with increasing failure rate on average (IFRA) distributions, the exponential approximation proposed in a recent paper always underestimates the MTBF; hence, it is a lower bound at best. The proposed approximation and bounds are applicable for a wide range of systems because systems which contain components with exponential or any increasing failure rate (IFR) distribution (viz., Weibull with$beta≫1$, gamma, Gumbel,$s$-normal, and uniform) follow an IFRA distribution. As a special case, the proposed bounds & approximations provide better results for systems that contain only exponential failure distributions.     

利用频域时钟抖动分析加快设计验证过程

随着数据速率的提高,时钟抖动分析的需求也在与日俱增。本文探讨参考了时钟的作用和时钟抖动对数据抖动的影响,并讨论在E5052B信号源分析仪（SSA）上运行的Agilent E5001A精确时钟抖动分析应用软件所配备的全新测量技术。     

Analysis of Dielectric Periodic Structures with Multi-Mode Network Method

The transmission characteristics of several dielectric periodic guiding structures are analyzed in this paper with a method, which the rigorous mode matching method is combined with the multimode network theory. The precision and effectiveness of the present method are verified by experimental data.     

An Analysis of Log Periodic Antenna with Printed Dipoles

An analysis of Log Periodic Antenna with Printed Dioples is presented here. In this analysis, the wave equation for Hertz potential is solved in Cartesian coordinates applying the boundary conditions of a flat strip diople. Using this model, the input currents to the antenna elements, the current distribution of the antenna elements, and the radiation pattern are computed. The computed results are compared with experimental results.     

图形化显示分析时钟系统结构

随着超大规模集成电路的时钟系统结构日趋复杂,如何清晰明了地表示时钟结构和相互关系成为了业界关注的焦点。本文提出一种图形化显示分析时钟系统结构的方法,在一个图形窗口内即能显示时钟系统的整体结构：利用树型时钟列表表示时钟之间的相互关系;利用标尺指示时序信息和逻辑层次;在显示单元连接关系的时钟结构中,利用符号突出特征单元和特征属性,支持不同颜色高亮显示检查结果以及关键字的查询结果。模块化的抽象方法采用过滤了复杂时钟系统中的次要信息,突出时钟的代表性结构特点,从而有效地化简了主窗口的显示内容。