一种双端口CICQ交换机的分组调度方案

Internet 中的交换机面临着高速交换和提供QoS保证的双重挑战,前者要求交换机的缓存以线速工作,后者要求交换机能完全模仿输出队列交换机。目前交叉点缓存交换机仿真输出队列交换机的方案需要交换机内部加速2倍,对硬件实现要求较高。该文利用双端口技术,提出了一种新型的交叉点缓存交换机结构,理论分析说明,该变长分组交换机在无需内部加速的情况下能够仿真输出队列交换机,并且交叉点缓存的需求是有下界的,从而表明该交换结构适合高速交换。     

两级交换机中分组有序到达算法研究

为了提高高性能分组交换机的扩展性,张尚正等人提出了一种称为负载平衡交换机(load-balancedswitch)的交换结构,该交换机分为两级交换结构,每一级都采用一种时序固定的连接方式,具有良好的扩展性;同时可以提供100%吞吐量保证。但是,负载平衡交换机的基本结构会出现分组乱序的情况。本文提出了一种在两级负载平衡交换机中保证分组顺序到达的满帧填充算法,该算法具有良好的交换特性(平均时延及吞吐量),同时也是一种分布式算法,各个端口可以独立地进行操作。     

集中式用户交换机

用户交换机 （ＰＢＸ）是一种专用 交换机,它完成企业内部之间以及与外部的电话交换,是市通信网的主要组成部分。随着通信技术的发展,特别是程控交换技术的不断发展,出现了一种新的用户交换机形式——集中式用户交换机（ＣＥＮＴＲＥＸ）。 集中式用户交换机是将原先建立于用户端的用户交换机并入公用网,以局用交换机替代原用户交换机,并保留用户交换机原有的基本功能。集中式用户交换机业务是在局用交换机上开发的新业务,它主要用于本地网内准备新建、改建、扩建用户交换机的企事业。根据用户需求,利用局用交换机软件功能,将若…     

ATM交换结构及其特点

ＡＴＭ技术已被公认为下一代网络世界的核心技术，ＡＴＭ交换机是组成ＡＴＭ网络的关键部件。文章详细讨论了ＡＴＭ交换机的各种交换结构，比较它们的优缺点，提出一种修正的Ｂａｔｃｈｅｒ－ｂａｎｙａｎ交换结构。     

一种新的基于旁路队列Banyan交换的ATM交换机结构的设计与性能分析

提出了一种新的基于旁路队列Banyan交换的ATM交换机结构,既适合于单播情况,又适合于多播情况,复杂度也比较低。本文详细讨论了交换机吞吐量的一种新算法,并依据此算法对该交换机进行了性能分析。     

数字程控用户交换机EAST8000

EAST 8000数字程控用户交换机是华为公司追踪世界先进技术,分析研究了国内外多种交换机,以世界一流交换机设备为目标,按照国标、部标独立研制成功的系列数字程控交换机之一。整机设计符合《邮电部电话交换设备总技术规范书》及《自动用户交换机进网要求》(YD-344)的要求,是一种中、大型的用户交换机,既适用于模拟网,又适用于数模混合网和数字网,还可组成各种专网,供大型厂矿、医院、大专院校等企事业单位以及     

虚拟交换机（Centrex）

虚拟交换机（Ｃｅｎｔｒｅｘ）赵敏Ｃｅｎｔｒｅｘ是一种集中交换业务，又称虚拟交换机，是数字程控交换机所具有的一种功能，是当今电话通信中最新应用技术。Ｃｅｎｔｒｅｘ意思是在用户端不装任何小交换机，而由数字程控交换机直接向这个企业提供所有电话，可做到虽无小...     

浅谈ISDN交换机

ISDN交换机是在现有数字程控电话交换机的基础上改进而成的。目前，一般的数字程控电话交换机只能进行电话交换，而且其用户线接口是模拟的，为了适应ISDN端到端的数字传输，将其改为ISDN交换系统，主要需进行3方面的改进：（1）要能实现数字接入；（2）要能进行D信道处理；（3）要能进行对分组数据的交换或能与分组交换网进行互通。因此，ISDN交换机的软件和硬件结构都要比一般数字程控电话交换机复杂得多。ISDN交换机结构示意图如图1所示。1．用户和中继线接口（L／T）ISDN交换机的用户接口有模拟用户接口和数字用户接口。模拟…     

光纤通道交换结构及其配置功能研究

对光纤通道交换结构拓扑作了简要介绍和说明,进而从整个交换结构的配置功能出发,分析讨论其建立链路参数和交换端口操作模式,选择主要交换机、分配领域标识符、分区合并和路径选择的过程,并同时给出状态转移图,研究重点放在主要交换机对领域标识符的分配上.     

光纤通道交换机接口的设计与实现

随着企业数据存储量的迅猛增长,对光纤通道交换机的数据转发速率要求越来越高.高速的交换机首先需要高速的接口.设计了一种基于FPGA的、通道速率达到2Gb/s的光纤通道交换机接口.对设计进行功能仿真,测试了其逻辑功能,并通过16×16光纤通道交换机的FPGA实现,验证了接口的功能和数据传输速率.     

Method of improving switching speed

The saturation characteristic of a switching transistor can be improved by using gold doping, buried layers, or clamp circuits. However, some important factors such as switching speed, loading capability, cost, and reliability may have to be sacrificed. The author describes a new technique to significantly improve not only the saturation characteristic, but also the switching speed by utilizing a two-collector-terminal transistor. The TCT structure and theory are presented. Results of experiments using the TCT and the conventional transistor are compared.     

VCSEL polarization modulation for pulse-per-second clock signal transfer in optical frequency distribution systems

In this paper, a novel vertical cavity surface emitting laser (VCSEL) polarization modulation technique based on polarization switching due to thermal heating in a single transverse mode class 10 G VCSEL at 1 310 nm is demonstrated experimentally. The inherent orthogonal polarization switching of the VCSEL carrier with changing bias is exploited in the transmission of pulse-per-second (PPS) timing clock signal. Experimental results show that PPS pulse widths of 9.97 μs and 9.98 μs are measured for back-to-back analysis and over 3.21 km of G 652 urban fibre transmission, respectively. This work provides a novel alternative for adoption in optical frequency and time transfer applications.     

On the speedup required for a multicast parallel packet switch

A parallel packet switch (PPS) is a switch in which the memories run slower than the line rate. Arriving packets are load-balanced packet-by-packet over multiple lower speed center stage packet switches. It is known that, for unicast traffic, a PPS can precisely emulate a FCFS output-queued (OQ) switch with a speedup of two and an OQ switch with delay guarantees with a speedup of three. In this paper we ask: is it possible for a PPS to emulate the behavior of an OQ multicast switch? The main result is that for multicast traffic an N-port PPS can precisely emulate a FIFO OQ switch with a speedup of S>2√N+1, and a switch that provides delay guarantees with a speedup of S>2√(2N)+2     

Low-Voltage Bootstrapped CMOS Drivers With Efficient Conditional Bootstrapping

In this paper, a set of low-voltage bootstrapped CMOS drivers are presented to reduce power consumption and improve switching speed for driving a large capacitive load. The proposed drivers can reduce the power consumption by making bootstrap operations conditional to input statistics. They also improve switching speed by providing larger bootstrap voltages for the same amount of integrated bootstrap capacitance as compared with conventional bootstrapped drivers. The proposed drivers were designed using 0.18- CMOS technology. The comparison results indicate that the proposed drivers achieve power savings up to 97% with 13%-22% improvements on switching speed as compared with the conventional design.     

Performance study of an input and output queueing ATM switch with a window scheme and a speed constraint

In this paper, we study the performance of an input and output queueing switch with a window scheme and a speed constraint. The performance of a non-blocking ATM switch can usually be improved by increasing the switching speed. Also, the performance of a switch can be improved using a window scheme by relaxing the first-in-firstout (FIFO) queueing discipline in the input queue. Thus, one can expect that a combined scheme of windowing and a speed constraint can improve further the performance of the packet switch. Here, we analyze the maximum throughput of the input and output queueing switch with a speed constraint combined with windowing, and show that it is possible to obtain high throughput with a small increment of speed-up and window size. For analysis, we model the HOL queueing system as a virtual queueing system. By analyzing the dynamics of HOL packets in this virtual queueing model, we obtain the service probability of the HOL server as a function of output contention capabilities. Using the result, we apply the flow conservation relation to this model and obtain the maximum throughput. The analytical results are verified by simulation.     

分数阶傅里叶变换的多项式相位信号DOA估计

针对多项式相位信号波达方向(DOA)估计研究较少的问题,提出了一种基于分数阶傅里 叶变换(FRFT)的多项式相位信号(PPS)的DOA估计算法。该算法首先通过多项式相位变换,估 计出PPS的最高阶相位系数,从而可以消除最高阶项。运用这一降阶思想,依次消除高阶项 ,这样PPS可降为线性调频(LFM)信号,然后将宽带的LFM信号转化为分数阶Fourier域窄带的 平稳信号。在相应的分数阶Fourier域,运用求根MUSIC算法对信号进行DOA估计,从而把LFM 信号的DOA估计推广到了PPS的DOA估计。理论分析和仿真实验表明,该方法能很好地估计出P PS的DOA,并且简洁。     

Rise Time and Gain Fluctuations of an Electrooptical Amplified Switch Based on Multipulse Injection in Semiconductor Optical Amplifiers

Subnanosecond electrooptical switching times with 26-dB extinction ratio were obtained by using semiconductor optical amplifiers driven by a multipulse injection current. The multipulse switching current was generated by superimposing fast electronic pulse signals in a microwave resistive combiner. Although very fast switching is achievable, nonlinear behavior and circuits parasitic induce gain fluctuations and overshooting during the off–on process. Theoretical and experimental results show that the reduction of parasitics is an important parameter for improving the switching performance. The multipulse injection technique can improve the switching speed for a chosen degree of overshoot.      

ANALYSIS AND DESIGN OF THE STABLE PARALLEL PACKET SWITCH

This paper analyzes the Parallel Packet Switch(PPS) architecture and studies how to guarantee its performance. Firstly a model of Stable PPS (SPPS) is proposed. The constraints of traffic scheduling algorithms, the number of switching layers and internal speedup, for both bufferless and buffered SPPS architecture, are theoretically analyzed. Based on these results, an example of designing a scalable SPPS with 1.28T capacity is presented, and practical considerations on implementing the scheduling algorithm are discussed. Simulations are carried out to investigate the validity and delay performance of the SPPS architecture.     

GPS驯服中无偏滑动平均滤波算法的研究

 分析已有GPS驯服中滤波算法的特点,提出了基于GPS的实时频率误差处理及状态估计的无偏滑动平均滤波算法.该方法继承了普通滑动滤波算法低噪声特点,且用线性回归估计补偿了普通滑动滤波算法的偏差,利用该方法滤除频率测量误差中的频率偏差和多通道GPS接收机秒信号(GPS1PPS)的锯齿误差,并预报晶振状态.MATLAB仿真和实际测试结果都证明了无偏滑动滤波算法比普通滑动滤波有效,提高了晶振频率的长期稳定度和准确度,实际系统中恒温晶振OXCO-131的长期频率稳定度的Allan方差提高了约三个数量级,达到3.5E-12/d.     

Soliton Interaction in Optical Soliton Switching

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