Optical transmission research

The availability of coherent sources producing usable amounts of power in the optical frequency range has stimulated considerable research in optical communications. Devices such as oscillators, modulators, detectors, and ancillary apparatus having desirable characteristics exist and are being used to design and build prototype terminals. Two possible media are being studied and means are being sought to improve their performance. They are 1) through-the-atmosphere propagation and 2) enclosed media with appropriate focusing and directing elements. Experimental optical transmission systems can readily be assembled with information capacities in a single RF channel comparable to those of microwave radio or millimeter waveguide. Such optical systems are not yet competitive for high reliability common carrier service because 1) long-distance transmission techniques of adequate reliability have not yet been advanced, and 2) optical repeater components are not yet competitive with their lower frequency counterparts. Some features characteristic of optical transmission systems are reviewed in this paper, along with a brief indication of the state-of-the-art for major components.     

Reliability and performance of tree-structured grid services

Grid computing is a new emerging technology aiming at large-scale resource sharing, and global-area collaboration. It is a next step in an evolution of parallel and distributed computing. Due to the large scale and complexity of the grid system, its performance and reliability are difficult to model, analyse, and evaluate. This paper presents a model that relaxes some assumptions unsuitable for grid computing systems that have been made in the existed works studying the distributed systems. The paper proposes a virtual tree model of the grid service. This model simplifies the physical structure of a grid service, allows service performance (execution time) to be estimated, and takes into account the common cause failures in communication channels. Based on the model, an algorithm for evaluating the grid service performance distribution and the service reliability indices is suggested. The algorithm is based on graph theory, and Bayesian analysis. Illustrative examples are presented in which the results of the suggested algorithm are compared with simulation results.     

Optimal Resource Allocation for Maximizing Performance and Reliability in Tree-Structured Grid Services

The paper considers a grid computing systems in which the resource management systems (RMS) can divide service tasks into execution blocks (EB), and send these blocks to different resources. To provide a desired level of service reliability, the RMS can assign the same EB to several independent resources for parallel (redundant) execution. According to the optimal schedule for service task partition, and distribution among resources, one can achieve the greatest possible expected service performance (i.e. least execution time), or reliability. For solving this optimization problem, the paper suggests an algorithm that is based on graph theory, Bayesian approach, and the evolutionary optimization approach. A virtual tree-structure model is constructed in which failure correlation in common communication channels is taken into account. Illustrative examples are presented.     

Software bugs and communications system performance

Software bugs and their manifestations are of concern in real-time systems such as communications systems. The reliability modeling of these systems has generally defined hardware performance models in great detail but only specified an estimate for the software performance. Software reliability modeling is usually based on the number of software bugs and not based on bug manifestations. The ultimate service provided by communications systems is dependent upon the level of criticality of bug manifestations and the frequency of occurrence of these manifestations. This paper discusses the current trend for the qualification and quantification of communications systems performance with emphasis on software bug manifestations.     

Establishing reliability and availability criteria forfiber-in-the-loop systems

Telephone service reliability and availability are examined historically. Availability objectives for fiber-in-the loop (FITL) systems are examined. Network, system, and component considerations are discussed. The problems raised by environmental conditions encountered by FITL systems are described, and the need for adequate reliability testing is discussed     

Compatibility and Simplicity: The Fundamentals of Reliability

Complex systems are less compatible internally, and with other systems, which reduces reliability. To restate, two primary principles must be kept in mind: keep the system simple, and make the system compatible with others. These two guidelines will help maintain the desired reliability.     

网管系统可靠性指标分配方法研究

为了研究网管系统可靠性指标分配,介绍了几种系统可靠性基本模型、特点和使用的系统,提出了可靠性指标分配的方法和原则,并进行了案例研究。针对特定通信网的综合网络管理系统功能,构建了该网络管理系统的可靠性模型,并依据研制合同中规定的可靠性指标要求进行可靠性指标分配,给出了满足研制总要求的可靠性指标分配结果,解决了网管系统可靠性指标分配关键技术。     

播出系统可靠性分析和提高可靠性的方法

使用数学方法对串行系统和并行系统的可靠性进行了定量分析并给出了计算实例.归纳了系统失效的规律,并结合分析结果提出了播出系统的设计原则,最后提出了提高播出系统可靠性的方法.     

云存储系统中数据副本服务的可靠性保障研究

以数据节点与网络链路的可靠性因素分析为基础,提出了云存储系统的数据副本服务可靠性模型。根据访问可靠性与数据副本数量、用户访问量之间的关系,设计数据服务可靠性、副本生成时机、存储节点选择的确定方法,实现了副本分布、删除算法,并在云存储系统ERS-Cloud上进行一系列实验,结果表明该方法能够有效保障数据服务的可靠性,进一步降低副本的冗余存储数量。     

Disaster prevention measures of NTT for telecommunications networksystems

In Japan, earthquakes and other natural disasters such as typhoons and heavy rains occur frequently. Developing measures to prevent communication interruptions caused by natural disasters, especially earthquakes, is a major priority of telecommunication service companies. Recent disaster damage in Japan is outlined, and preventive measures being taken by Nippon Telegraph and Telephone (NTT) are described. NTT's design guidelines are based on three fundamental principles: improving network reliability, whereby facilities are physically reinforced and strengthened; preventing isolation, ensuring that communication with disaster-stricken districts is constant; and rapidly restoring services. Each of these principles and the methods used for their implementation are discussed     

Reliability and Performance of Star Topology Grid Service With Precedence Constraints on Subtask Execution

The paper considers grid computing systems with star architectures in which the resource management system (RMS) divides service tasks into subtasks, and sends the subtasks to different specialized resources for execution. To provide the desired level of service reliability, the RMS can assign the same subtasks to several independent resources for parallel execution. Some subtasks cannot be executed until they have received input data, which can be the result of other subtasks. This imposes precedence constraints on the order of subtask execution. The service reliability & performance indices are introduced, and a fast numerical algorithm for their evaluation given any subtask distribution is suggested. Illustrative examples are presented.     

System Considerations for Short-Haul Multichannel Subscriber Carrier

Solid-state technology is available to permit the design of multichannel station carrier systems with "prove-in" distances of 18 kft or less. Customer acceptance of these systems will depend on transmission performance, installation and maintenance ease, service reliability, and application restriction, as well as the per-channel installed cost. This paper discusses these parameters with regard to digital and analog carrier and carrier-concentrator systems.     

Fundamental limitations caused by RF propagation

Propagation phenomena affect the design of radio frequency (RF) transmission systems. Propagation phenomena limit the suitability of portions of the frequency band for some applications, limit the reliability of RF transmission systems, and provide a means of coupling unwanted signals from one system to another with the potential of producing interference. The possiblity of interference is the fundamental limitation to the unrestricted use of the frequency band. Phenomena affecting suitability, reliability, and the potential for interference are considered for frequencies in the 1- to 300-GHz range.     

针对前向纠错编码的脉冲干扰技术研究

数字通信系统通常采用前向纠错编码提高系统可靠性,传统干扰方法针对采用前向纠错编码通信系统的干扰效果较差,为了克服此缺点,提出了通过控制错误分布的脉冲干扰方法。分析了典型卷积码和RS码的纠错能力,根据2种纠错编码的特性分别探讨了干扰信号设计原则和方法。计算机仿真表明,针对不同的编码样式采用特定脉冲干扰参数,能够取得更好的干扰效果。     

Computer intrusion detection through EWMA for autocorrelated and uncorrelated data

Reliability and quality of service from information systems has been threatened by cyber intrusions. To protect information systems from intrusions and thus assure reliability and quality of service, it is highly desirable to develop techniques that detect intrusions. Many intrusions manifest in anomalous changes in intensity of events occurring in information systems. In this study, we apply, test, and compare two EWMA techniques to detect anomalous changes in event intensity for intrusion detection: EWMA for autocorrelated data and EWMA for uncorrelated data. Different parameter settings and their effects on performance of these EWMA techniques are also investigated to provide guidelines for practical use of these techniques.     

Designing a Reliable Power System: Hydro-Quebec's Integrated Approach

Hydro-Que/spl acute/bec's transmission system is among the most extensive and complex transmission networks in North America. The system's design was improved over the last few years using an optimization process based on acquired experience as well as customers' expectations. Hydro-Que/spl acute/bec's transmission system is currently designed in accordance with four major guiding principles based on a successive line of defense concept designed to counter events that are increasingly more severe but also increasingly more rare. These major guiding principles are a direct reflection of the level of risk that society accepts to tolerate in relation to the costs involved by higher reliability requirements. Que/spl acute/bec's specific context, which is characterized by long transmission lines, harsh weather, and customers' heavy reliance on electricity for their heating needs, means that very high security standards must be used in the system design. To obtain a level of reliability on par with that of our neighbors' systems, however, requires more stringent criteria and standards. This paper will describe the design philosophy of Hydro-Que/spl acute/bec's power system, the underlying major guiding principles, and the defense plans designed to ensure its reliability.     

多卫星导航系统组合定位解算

主要研究由GPS、Galileo和北斗等多个卫星导航系统互相辅助,实现组合定位解算。由于各独立卫星导航定位系统的卫星星座规模有限,可提供的卫星定位服务的精度、可靠性无法得到保障。为了提高定位精度,在传统卫星定位解算的理论基础上,提出了利用多种系统组合定位的方法,可明显改善可见卫星结构,提高定位精度,从而保证定位结果的可靠性和连续性。     

用于红外系统的制冷机比较

从制冷量、制冷温度、能量指标、寿命、重量、机器的复杂程度、振动情况、维修操作是否方便、长期运行能否安全可靠、初投资及可否一机多用等方面评价制冷机。从而选择出适于红外热成象系统的制冷机,以便进行研制并扩大其应用范围。     

广播电视时钟系统的设计与实现

简述广播电视时钟系统的设计原则、工作原理、设备结构功能,分析本时钟同步系统的先进性、可靠性、实用性。     

Phase-locked loop techniques. A survey

Phase-locked loop (PLL) is a technique which has contributed significantly toward the technology advancement in communication and motor servo control systems in the past 30 years. Inventions in PLL schemes combined with novel integrated circuit (IC) technology have made PLL devices important system components. The development of better modular PLL ICs is continuing. As a result, it is expected that they will contribute to the improvement in performance and reliability of future communication systems. They will also contribute to the development of higher accuracy and higher reliability servo control systems, such as those involved in machine tools. This paper provides a concise review of the basic PLL principles applicable to communication and servo control systems, gives the configurations of PLL applications and reports a number of popular PLL chips