T-S-T三级交换网络路径搜索算法的研究

这几年光纤通讯技术的飞速发展使得目前高速通讯网络性能的瓶颈集中在高速交换系统,研究、设计和制造高速交换系统对目前高速通讯网络具有极其重要的意义.提出一种新的三级交换的矩阵模型,在这种模型上设计无阻塞交换算法.介绍这种T-S-T网络的调度算法的实现和实验结果.算法设计和实现的过程中,大量的实验表明,该算法具有良好的特性,而且通过芯片级联可实现.     

Research Model for Time-Separation Integrated Communication

A new communication system concept which is an important step toward an all-digital telecommunication plant is discussed. A research model, called ESSEX (Experimental Solid State Exchange), which combines remote line concentration, time-separation switching and PCM transmission is introduced to demonstrate the concept. The model, which uses solid state devices, works at the speed of a full-size system.     

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.     

多模光纤模式群分集复用系统

多模光纤(MMF)已成为"最后一千米"短距离通信的理想介质,但多模光纤的模间色散限制了其传输能力.模式群分集复用(MGDM)是种光路的多输入多输出(MIMO)技术,该技术利用多模光纤中不同的模式群作为相互独立的信道来传输多路信号,极大地提升了多模光纤的传输能力.设计实现了一个基于75 m梯度型多模光纤(GIMMF)直接检测的两路MGDM通信系统,不同模式群的激发利用选择模式激发实现,利用偏置连接器和多模耦合器实现模式群的复用及解复用,并利用该系统实现了模拟视频信号和非归零码(NRZ)数字信号的传输.     

Computer simulation of a converter-fed DC drive using thetransmission-line modeling technique

A modeling technique for the discrete time domain analysis of power electronics and drive systems is discussed. A discrete model for a converter-fed DC motor drive system has been developed and simulated using this technique. All system components, including the DC machine and power converter, are modeled in a discrete manner as a network of transmission line sections with the same characteristics as the drive system. The technique isolates the nonlinearity due to the devices' switching action from the system equation and enables a constant system matrix to be used irrespective of the switching state of the power circuit. The algorithm developed provides an exact solution to the discrete model and is easily implemented on desktop computers     

通信综合实训系统的设计与实现

根据普通高等院校以及通信类大公司的通信专业技能的实训需求,提出了一个通信综合实训系统设计方案。该系统包括接入、传输、程控、软交换和移动通信五大实验模块,涵盖了现代电信网的主要技术层面,具有成本低、部署方便、功能丰富等特点。     

大功率LED的脉冲响应及其大电流光调制技术研究

LED作为可见光通信(VLC)的发射光源时为保证足够 大的光信号覆盖范围和信号强度,应采用大电流脉冲调制。本文研究了大功率LED的光 -电脉冲响应比小功率器件较慢、从而造成光调制带宽降低的原因,以及LED注入电 子和空穴的缓慢复 合与驱动电路晶体管在大电流工作时的存储效应;由此设计了FPGA控制下的光脉冲整形方案 ,信号脉冲经由FPGA再生同时产生另外两路相位关联的短脉冲,同步控制驱动电路分别 在信号脉冲上 升沿施加一个瞬时高压加速载流子注入,在脉冲下降沿使LED两端短路将剩余载流子泄放, 使光脉冲边沿加速进行整形。对接收信号 的眼图和误码率(BER)的测试结果表明,在接近安培量级的 峰-峰值调 制电流下,通过这种同步控制方法使光信号质量得到有效改善,传输速率得到明显提高。     

What is telecommunications circuit switching?

This article is an attempt to provide one with no knowledge of telecommunications circuit switching with some insight into its complexity and technological progress. This subject has for many practicing telecommunication engineers been treated as enigmatic. The problem is that switching is a combination of many details. The power of modern technology has added to the complexity of the features and services that can be offered economically by these systems. Perhaps in no other area of telecommunication does the evaluation of the choice of technology and system architecture so obfuscate the true purpose of the system. The functional requirements of a switching system are relatively simple and easily understood, but the service and feature requirements are growing and being implemented at a rate greater than ever before. With its growth has emerged a new era of switching. It is the desire of the author to place the past and current technology, as well as the fundamentals into prospective so that the reader may be prepared for the new era in telecommunication circuit switching.     

基于uClinux的嵌入式系统在通信用高频开关组合电源监控中的应用

uClinux操作系统和ARM微处理器的结合是工业控制领域的有效方案,该方案实现了对通信高频开关组合电源的监控,不仅使嵌入式电源监控系统具有丰富的网络功能、灵活的软硬件扩展性能,而且使通信电源具有良好通用性、稳定性和可靠性。     

An efficient algorithm for the link allocation problem on ATM-basedpersonal communication networks

The personal communication network (PCN) is an emerging wireless network that promises many new services for the telecommunication industry. The proliferation of demands for extending wireless services to integrated services which supports the transmission of data and multimedia information has resulted in the need for broadband wireless systems that are able to provide service capabilities similar to those of wireline networks. The ATM cell-relay paradigm is one possible approach to provide broadband wireless transmission with PCNs using the ATM switching networks for interconnection of PCN cells. In an ATM-based PCN, the communication path between a pair of mobile terminals might be elongated due to the mobility of the terminals. The link allocation problem is that of allocating backbone links among ATM switches to reduce the effects of terminal mobility on the performance of ATM-based PCNs. Huang and Wang (1997) have shown that this problem is NP-complete. In this paper, we propose a new efficient heuristic algorithm for the link allocation problem. One novel feature of our algorithm is that we are able to derive sufficient conditions under which our algorithm is able to guarantee optimal solutions. Our empirical study shows that the average lengths of communication paths obtained by our algorithm are shorter than those obtained by Huang and Wang's algorithm. In addition, the number of successfully established paths obtained by our algorithm is significantly more than that obtained by the aforementioned     

一种高速低功耗ECL多模分频器的设计

本文介络一种高速低功耗ECL多模分频器的电路原理、电路和版图设计特点、工艺技术及研制结果。该分频器设计了0.5mA的内部开关电流和350mV的内部逻辑摆幅,输入输出均采用互补驱动。电路分频模数多,频率高,功耗低,典型功耗75mW,为相同集成度的普通ECL电路功耗的1/30～1/40。该电路广泛用于通讯、仪器仪表和频率合成器等领域。     

Power Line Communication in Digitally Controlled DC–DC Converters Using Switching Frequency Modulation

This paper investigates power line communication (PLC) in digitally controlled high-frequency switched-mode power supplies in distributed architectures that share the same bus voltage. Communication between different DC-DC converters is obtained by using switching frequency modulation and by detecting the switching signal on the common supply bus voltage. In case of low power transmission, a small duty-cycle perturbation at half of switching frequency is added to enhance the energy of the transmitted signal. Each converter operates at three different switching frequencies: the first is associated with bit 1 transmission, the second is associated with bit 0 transmission, and the third is associated with no transmission state. In the proposed solution, there is no need for an additional power amplifier in order to inject the communication signal on the power lines, but the signal used for the PLC is inherently generated by the pulsewidth modulation of DC-DC converters. Even if aimed at a dedicated digital IC, the communication architecture has been implemented in field-programmable gate arrays. Simulation and experimental results on DC-DC synchronous buck converters confirm that the performance is achievable by the proposed PLC techniques.     

Coupled-Filter-Inductor Soft-Switching Techniques: Principles and Topologies

Pulsewidth-modulation inverters and rectifiers are required in widespread applications such as energy-storage power plants, telecommunication systems, and electric-vehicle propulsion systems. Some of the stringent requirements of these applications can be achieved by high switching frequency. On the other hand, the use of high switching frequency may degrade the overall system efficiency, which can be alleviated by the utilization of soft-switching techniques. In this paper, a generic soft-switching diagram that can generate topologies for turn-on snubber, zero-voltage transition, zero-current–zero-voltage transition inverters with coupled filter inductor is proposed. This approach facilitates the understanding of these techniques by both newcomers and senior engineers, making the advantages and disadvantages of each soft-switching technique much clearer.      

Frame-Loss-Free Optical Line Switching System for In-Service Optical Network

Fiber-to-the-home (FTTH) has now reached the stage where it is providing real-time broadband services. Since even a temporary suspension of broadcasting and telephone services cannot be permitted, it has become important to improve the reliability of FTTH network operation. We have developed an advanced optical line switching system that diverts transmission signals from an in-service line to a spare line without interrupting communication. This system is realized by equalizing the transmission times of the signals sent through dualized lines composed of an in-service line and a spare line. The transmission times are equalized by employing two techniques in the dualized lines. One is a technique that uses a free space optics system to tune the optical line length continuously. The other is a technique for measuring a wide range of time differences between signals transmitted through the dualized lines. Since the dualized lines have a Mach–Zehnder interference structure, the differences can be detected with high accuracy by employing dual-light interferometry. We applied this switching system to a gigabit Ethernet passive optical network (GE-PON) during transmission and succeeded in switching in-service lines without inducing any frame loss.      

Active Voltage control of IGBTs for high power applications

The operation of an insulated gate bipolar transistor (IGBT) in its active region is a well established technique for withstanding short circuits and also for dv/dt control. In this paper, we exploit the active behavior of the IGBT, applying a voltage feedback loop to the IGBT to control its switching. It is shown that adding a bias to the demand reference waveform shifts the IGBT into the active region and permits wide bandwidth operation over most of the switching transient. The operation of the IGBT is reported in detail, making reference to a selection of experimental waveforms for 400-A, 1700-V capsule IGBTs. The implementation required for control of such large IGBT modules and capsule devices for high power applications is described and discussed. It is concluded that the active voltage control method allows the operation of high power IGBT circuits to be closely defined.     

High gain power switching using field controlled thyristors

A technique for high gain power switching using field controlled thyristors is described. This technique uses a MOSFET connected in series with the FCT to control the current flow. The circuit exhibits normally-off behavior and is capable of operation at high voltages. The current through the FCT can be turned on and off by the application of a low voltage gate signal to the MOSFET. Turn-on and turn-off times of less than 1 μs have been observed at a current gain of over 30. The new gating technique offers the advantage of the large operating current density of the FCT even at high breakdown voltages and the high input impedance of the MOS gate used to trigger the device during power switching.     

基于COM/DCOM技术的电信网络管理

本通过对TMN(电信管理网)思想以及COM／DCOM编程原理的分析，将COM／DCOM的功能特点与TMN电信网络管理的基本要求有机地结合在一起，提出了运用COM／DCOM技术建立TMN的基本设想，其原理是，将电信网的各种网元抽象为COM组件对象，组件对象实时反映所对应网元的各种特征数据，运用DCOM通信机制对这些组件对象及其特征数据进行监控管理，从而达到管理网元之目的。COM／DCOM的面向对象及分布式属性、操作系统和平台无关性、它的事件通知功能、高效的通信机制及其网络安全技术，均符合电信管理网络的功能要求。     

Unified approaches to integrated-service networks–burst and fast packet switching

The increasing demand for communication services, coupled with recent technological advances in communication media and switching techniques, has resulted in a proliferation of new and expanded services. Currently, networks are needed which can transmit voice, data and video services in an application-independent fashion. Unified approaches employ a single switching technique across the entire network bandwidth, thus allowing services to be switched in an application-independent manner. This paper presents a taxonomy of integrated-service networks, including a look at NISDN, while focusing on unified approaches to integrated-service networks. The two most promising unified approaches are burst and fast packet switching. Burst switching is a circuit switching-based approach which allocates channel bandwidth to a connection only during the transmission of ‘bursts’ of information. Fast packet switching is a packet switching-based approach which can be characterized by very high transmission rates on network links and simple, hard-wired protocols which match the rapid channel speed of the network. Both approaches are being proposed as possible implementations for integrated-service networks. We survey these two approaches, and also examine the key performance issues found in fast packet switching. We then present the results of a simulation study of a fast packet switching network.     

Ultrahigh-Speed Diode Switch for 50 GHz Band Utilizing Avalanche Breakdown in Varactor Diodes

Ultrahigh-speed switches for the 50 GHz frequency range utilizing avalanche breakdown in varactor diodes have been developed as transmitter-modulators for millimeter-wave PCM communication systems. By switching the diode between forward conduction and avalanche breakdown, better performance was obtained than with standard switching conditions. A typical switch of transmission type with a silver-bonded Ge varactor, GSB3C for an input power of +17 dBm at 48 GHz, gave an insertion loss of 3.5 dB with a maximum attenuation of 31 dB. Some of the distinctive characteristics of diode switches utilizing avalanche break-down in varactor diodes are discussed.     

Wireless information and power transfer using single and multiple path relays

A relay‐based wireless communication model can relay information along with the power bidirectionally using the amplify‐and‐forward scheme. This paper studies such model extensively. Three information and power relaying protocols, that is, time‐based switching relaying, power‐based splitting relaying, and hybrid time switching‐based and power splitting‐based relaying (HTPSR) are used to carry forward bidirectional information and power transfer. First, a solo relay model is studied, for which, we derived a throughput expression for end‐to‐end information transfer, and this is done for all the three relaying protocols. The paper indicates that the system throughput depends upon the time switching and the power splitting ratio. Further, to make the system more reliable and robust, multiple relays are used in the path. Various relay selection schemes are used for path selection in each transmission, thereby yielding different throughput performances. The results show that an optimal throughput is obtained for a given relay location at an optimal set of values of splitting and switching ratio. Moreover, the HTPSR outperforms both the power splitting and time switching protocol in system throughput performance for a single as well as a multiple‐relay model. Whereas, in relay selection schemes, the best SNR selection scheme outperforms in all the schemes used. The simulated results confirm that the system throughput is an active function of relay placement.