可生存网络系统的构建方法

在攻击、故障和意外事故存在的情况下，可生存的网络系统仍然具有提供连续、可靠的网络服务的能力．本文提出了构建可生存网络系统的方法，可以增强网络系统最重要的三个特性：抵御、识别和恢复，从而从整体上有效地增强了网络系统的可生存性．这种构建网络系统的方法使得网络系统的可生存性不再依赖于特定的系统组件，相应地保护了网络系统的应用．     

Advanced Modelling Techniques for Designing Survivable Telecommunications Networks

Near-future multimedia communications will require high-capacity networks employing optical WDM technology to simultaneously carry increasingly large numbers of broadband users. Fast and efficient restoration of network service after failure will be critical to maintaining customer satisfaction and ensuring business success.This paper discusses state-of-the-art software tools and algorithms developed by BTexact Technologies for automated design of such networks, planning of their restoration/resilience capacity, and calculating corresponding end-to-end service availability.The tools and underlying algorithms/models are largely technology independent, and may therefore be applied to a wide variety of scenarios. In this work, a generic network model representing an inter-city telecommunications network for a large European country is considered as a realistic test case.     

A Design Procedure for Bandpass Channel Multiplexers Connected at a Common Junction

A new general design procedure is presented for multiplexers having any number of Chebyshev channel filters, with arbitrary degrees, bandwidths, and interchannel spacings. The design procedure is developed for bandpass channel filters connected in series at a common junction for narrow-band applications. Commencing with the closed-form expressions for element values in Chebyshev filters, the multiplexer design process modifies all of the elements in each channel filter and preserves a match at the two points of perfect transmission closest to the band edges of each channel filter, while taking into account the frequency dependence across each channel. Examples of several multiplexer are given indicating that the design process is valid for most combinations of contiguous and noncontiguous channels.     

利用广电光纤网络实现局域网互联的规划与设计

主要讨论了在有线电视现有HFC光纤网络上进行计算机网络互联的一种方案，并且详细叙述了在网络设计过程中网络拓扑结构的建立、IP地址的划分、3层交换机以及光纤收发器的安装与配置。实践证明，在现有HFC网络上利用光缆备份纤进行计算机网络的互联是有线电视网络多功能开发业务的一种发展方向。     

基于灾难预测多区域故障的虚拟光网络生存性映射

生存性虚拟光网络映射是提高光网络应对灾难故障的重要技术保障措施。为解决灾难性多区域故障导致弹性光网络的带宽容量损失问题,该文提出基于灾难预测故障模型的蚁群优化虚拟光网络映射 (DFM-ACO-VNM)算法。在该算法中,设计基于光节点资源和相邻链路的全局潜在故障概率的光节点排序映射准则,并设计启发式信息公式实现多区域故障下最小带宽容量损失的虚拟节点和虚拟链路协同映射。仿真结果表明,该文所提算法在多区域故障时能降低带宽容量损失,减少带宽阻塞率和提高频谱利用率。

     

A Routing Procedure for the TIDAS Message-Switching Network

In this paper an investigation of some routing methods suitable for a special computer communication network called TIDAS-T, in which the traffic exchange is done according to the store and forward message-switching technique, is elucidated. The properties of different routing procedures and sensitivity of some parameter settings during the various conditions, that may occur in this network, have been studied by simulations with a specially made model for the TIDAS-T computer network. It has turned out that due to the requirements for TIDAS the best routing procedure is a one-parametric adaptive method, which has built-in instruments to adapt to the different situations that can arise in the net, for instance, when line and/or node errors occur. This procedure is in principal similar to the one used in the Advanced Research Projects Agency (ARPA) net. However, some extensions and added features, such as the introduction of the concepts split horizon, immediate updating mode and skipping constant, have given the procedure more power to react on complex net errors and to reduce circulating traffic. The method is in principal quite general and will therefore be suitable for many other message-switching computer networks. However, the parameter settings in the procedure are specially tuned for this network by simulation runs.     

一种低旁瓣混沌雷达波形设计方法

传统的线性调频雷达波形,其自相关函数旁瓣较高,虽然可以经过切趾滤波处理降低旁瓣,但有一定程度的信噪比损失。针对这一问题,本文提出利用初始值优化过后的Lorenz系统的变量进行混沌调频,不但可以得到更好的自相关特性,而且没有信噪比损失,同时保持了混沌信号的类随机特性和较强的抗干扰性能(ECCM)。仿真结果表明,在没有加窗处理的情况下,可得到具有-39.53dB峰值旁瓣的Lorenz混沌调频雷达信号,比切趾滤波后的线性调频波旁瓣更低,是理想的雷达信号。     

用非线性光纤连接的长周期光栅对的光开关特性

提出用一根掺铒光纤连接两个对称的长周期光纤光栅(EDF-LPFG)对构成的新型全光开关.数值模拟了在交叉相位调制下对应于不同抽运功率的信号光的透射谱;还研究了在不同光栅的有效折射率调制幅度和光纤吸收系数下,信号光透射率随抽运光功率的变化.导出了器件的阈值开关功率公式.EDF-LPFG对光开关的阈值开关功率比单LPFG光开关的开关功率降低了5个数量级,不到25 mW.     

A Synthesis Procedure for Designing 90° Directional Couplers with a Large Number of Sections

A synthesis method for designing symmetrical directional couplers with an arbitrary realizable coupling is described. The method is based on a transformation of the coupling to the time domain, where the couplings of the different sections are easily identified. The fundamental operation of the method is the Fast Fourier Transform, which makes it very efficient in computer time and memory requirements. The method is illustrated by the design of a 8.34+-0.3-dB equal-ripple coupler with 201 sections.     

抗毁WDM网中单SRLG故障的共享子通路保护

该文针对抗毁WDM网中单个共享风险链路组(Shared Risk Link Group,SRLG)故障,提出了一种动态共享子通路保护(Dynamic Shared Sub-Path Protection,DSSPP)算法.DSSPP为每条业务请求选择一条工作通路后,按照参数m把工作通路划分成若干条等长的子通路,其中m为子通路的长度,并为每条子通路各选择一条SRLG分离的保护通路.如果两条子通路SRLG分离,则它们对应的保护通路可以共享相同资源.在进行路由选择时,DSSPP考虑了负载均衡度和资源共享度,因此能有效地提高资源利用率和降低业务阻塞率.仿真表明,DSSPP不仅能保护单SRLG故障,而且能灵活地在资源利用率(阻塞率)和保护切换时间之间进行性能折衷.     

A Framework for Differentiated Survivable Optical Virtual Private Networks

Wavelength division multiplexed (WDM) networks are matured to provide, scalable data centric infrastructure, capable of delivering flexible, value added, high speed and high bandwidth services directly from the optical domain. Optical virtual private networks (OVPNs) make use of the concept of highly reconfigurable nature of lightpaths offered by WDM, to create secure tunnels of high bandwidth across the intelligent WDM optical transport network. An OVPN is a private connection between two or more edge devices (access nodes), that allows a group of clients to fully exploit the flexibility of the switched intelligent optical network. However, OVPNs will not be a viable alternative unless they can guarantee a predictable bandwidth, availability, response time, and fault-tolerance to users. In this paper, we study the problem of dynamically establishing lightpaths for OVPNs over intelligent optical transport networks to provide varying classes of service based on the type of primary and backup lightpaths and the number of backup lightpaths, when each OVPN is specified by the desired logical connectivity and Class of Service. The type of primary and backup lightpaths determines the QoS parameters such as response time and bandwidth. Whereas, the number of backup lightpaths determines the level of fault-tolerance and availability of OVPN. Based on the service classes, any OVPN in the network falls into one of the six classes viz. single dedicated primary and single dedicated backup (SDPSDB), single dedicated primary and multiple dedicated backups (SDPMDB), single dedicated primary and single shared backup (SDPSSB), single shared primary and single shared backup (SSPSSB), single shared primary and multiple shared backups (SSPMSB), and best-effort (BE). In BE, we consider two variations—(1) OVPN as dedicated logical ring topology (DLRT) and (2) OVPN as shared logical ring topology (SLRT). We conduct extensive simulation experiments to compare and evaluate the effectiveness of different classes of OVPNs for varying network configurations–varying number of fibers, wavelengths on physical links, and number of nodes in OVPN.     

WLAN网络规划设计

随着WLAN网络的日益普及,网络规划的重要性越来越突出.本文从调研及勘查、覆盖设计、频率规划、容量规划、网络优化几方面对无线局域网的规划进行介绍和分析,为WLAN网络的部署提供参考.     

GPRS无线网络的规划设计

概括地介绍了GPRS技术特征及优势，阐述了GSM向GPRS网络演进方案，并对GPRS无线网络设计思路和方法进行了初步探索。     

光缆进线室列架设计之新理念

根据目前光缆进线室存在的问题，提出了光缆进线室设计的新理念，详细描述固话铜缆上线列架与光缆上线列架的不同之处，并对进线室的大小、上线列架的方式进行探讨．对双伸臂式列架进行全面的介绍。     

科尔沁区清河镇HFC网络设计方案

介绍通辽市科尔沁区清河镇有线电视发展的现状,提出清河镇有线电视网络的规划设计方案,对网络指标进行具体验算,并简要分析网络建设中光缆路由的敷设方式。     

SRAM静态低功耗设计

在标准的Fabless CMOS工艺线上,由于没有对静态存储器生产进行过专门的工艺优化,在有大规模SRAM嵌入设计的ASIC与SoC电路中,静态电流较大。文章讨论了静态存储器单元静态漏电模式,采用了国内某标准CMOS工艺线提供的0.25μm SPICE模型,使用HSPICE软件对六管静态存储器单元的静态漏电进行了模拟,介绍了一种高可靠、基于0．25μm标准CMOS工艺的低功耗静态存储器设计的解决方案,适用于要求低待机功耗的标准静态存储器、嵌入式静态存储器电路设计。     

一种低信噪比QPSK解调器设计方法研究

主要讨论了一种适用于较低信噪比情况下QPSK相干解调器的原理和实现方法,本方法以改进的costas环实现载波同步和以Gardner算法实现符号同步。讨论了costas的原理以及环相位误差提取、环路滤波器参数选取和相位模糊消除的方法,给出了此解调器的仿真结果和硬件测试结果。     

Intelligent Dynamical Buffer Scheduling Mechanism for Intermittently Connected Mobile Network

According to the store-carry-forward packet transmission method, nodes can communicate with each other in intermittently connected mobile network flexibly. As can be seen, the successful transmission of packets is assisted by multiple copies injected into the network. Therefore, the limited buffer should be utilized reasonably in this situation. In this paper, an adaptive buffer scheduling mechanism is proposed with the aid of packet transmission status estimation. According to the activity degree of node and the number of packet copies, the status of packet transmission in the network can be evaluated. Furthermore, with the estimated outcome of packet redundancy, the packets in the buffer are scheduled dynamically. Numerical results show that the activity degree can be estimated accurately, especially when the networks become larger. The number of packet copies can be proved that it follows normal distribution. Compared with other buffer scheduling mechanisms, our mechanism displays better performance, e.g., the packet delivery probability is enhanced by 21–50 %, and the latency is reduced by 15–23 %.