MPLS VPN在新闻制作系统网络中的应用

新闻制作的实际业务对网络架构有特殊的要求。为实现合理的隔离和开放，杭州电视台采用MPLS VPN技术搭建了安全高性能的新闻制作网，本文介绍了MPLS的工作原理及MPLS VPN技术，基于MPLS VPN技术设计新型架构新闻制作系统，包括系统结构、新闻制作网络VPN设计，实现功能等。     

CAD8903机芯的视频音频转换电路设计

本文概要介绍了CAD 8903机芯采用国产集成电路CD7680,CD74211,DG4053实现音频、视频切换功能的电路,并对CD7680中音频信号处理电路的特殊用法进行了说明。     

Implementation of multipoint connections in an ATM switching network

This paper presents the problems in the implementation of multipoint connections at switching level using the example of an ATM switching network. By choosing the proper routeing mechanism and the appropriate architecture of the switching element, a switching network can gradually be adapted to an increasing share of multipoint traffic. The first section describes the problems with the handling of multipoint connections within a multiple stage connection oriented switching network. In particular this refers to the routeing of the cells through the switching network. Several alternatives on this issue are discussed. Both, the selected approach based on a differentiated self-routeing mechanism and the corresponding cell format are introduced. In the second part of this article several switch architectures are compared in respect of their multipoint capability. It is demonstrated that at present the most promising solution are switching elements based on the principle of central buffering. A single chip solution using this concept is employed in the presented switching network.     

提高微机变电站综合自动化系统抗干扰能力的几项措施

在微机变电站综合自动化系统中,为了保证数字信号处理子系统采集到的信号有精度的频率、相位和足够的幅度,采用实验的手法,去观察和分析传感器输出信号、前置放大电路输出信号、电压比较电路输出信号、系统电源输出电压的波形等.根据不同电路信号频率、幅度和相位的特点与实际需要,利用LC低通无源滤波器和乘法器方式的功率因数纠正电路来过滤采集信号中含的杂波.利用窗口电压比较器使采集信号幅度位于两个指定的门限(参考电平)之间.使用这些措施得到结果是微机变电站综合自动化系统处理信号能力更准确、更快、更安全、更稳定.     

诺基亚西门子软交换容灾方案的应用及改进

对诺基亚西门子软交换容灾方案和原理进行了深入研究和分析,并对方案进行了改进。对改进后的实际测试情况进行了总结,从而证明改进方案可以大大缩短倒换所需时长。保证了软交换出现紧急情况下业务能迅速的切换和恢复。     

Optimizing offset times in Optical Burst Switching networks with variable Burst Control Packets sojourn times

In this paper, we consider the case of an Optical Burst Switching (OBS) network where the Switch Control Units (SCU) do not work at the peak rate. As a consequence, some Burst Control Packets (BCPs) will have to wait in queue to be processed, and then the BCP sojourn time will be variable. On the contrary, the optical burst does not leave the optical domain and the delay suffered is close to the propagation delay. Hence, chances are that the BCP arrives late to a given switch and, in that case, the optical burst will be dropped. We propose a Load-adaptive Offset Time algorithm (LOT) that takes into account the BCP variable sojourn time for the offset time calculation. The algorithm performs on-line calculation of the Discrete Fourier Transform (DFT) of the BCPs waiting time pdf. Our findings show that this procedure is very efficient both in terms of bandwidth usage and processing load. For example, considering a Gaussian service time for the BCPs, it turns out than less than 45 coefficients are necessary to calculate the offset time for a SCU utilization factor larger than 0.1.     

一种MPLS网络间的IP业务传送技术

当前跨多协议标记交换(MPLS)网络进行网间IP业务传送具有一定的局限性。详细描述了MPLS网络间辅以网关设备的IP业务传送技术,并提出接入网关和互连网关的设计方案,重点阐述了网关的模块组成和接口设计;结合在研的2种典型MPLS网络,利用AX4000测试仪对跨网的端到端IP业务传送性能进行分析,针对业务优先级和利用通道保护能力的IP业务传送指标进行测试,对测试数据和应用效果进行分析总结。     

城域网EPON承载IP基站回传的研究

随着3G移动互联网业务的发展,移动网络基站接口逐步呈现高速化、IP化趋势,在传统SDH网络无法满足基站承载需求的情况下,利用IP无线接入网（IPRAN）来实现3G移动基站承载已经成为技术演进方向。从节省网络投资成本及考虑到SDH网络现状等因素提出了利用城域网MPLS VPN及以太无源光网络接入技术来实现基站语音及数据业务的回传,探讨了基站回传组网中的各种安全保护技术,并通过现网测试验证了EPON接入技术承载基站回传业务的可行性。     

城域综合承载传送网的网络架构

随着业务和电信网络的IP化和宽带化,在城域（本地）网实现各种业务的综合承载传送已成为可能。根据各种承载业务的特点和网络现状,提出城域综合承载传送网络的目标网络架构、业务承载及网络演示方式。     

中性线的转换对UPS性能的影响和对策

由于低压配电系统接地故障保护（GFP）的需要,市电与备用发电机组电源转换电路必须采用4极自动转换开关（ATS）,而有些4极ATS在转换过程中存在中性线中断现象,严重影响了UPS的正常运行,由此引发的UPS故障和负载停电事件越来越受到关注。文中分析电信和数据中心常用市电和备用发电机组电源转换电路的性能及其对GFP和UPS运行的影响,提出工程实用解决方案。