【作者】 崔志刚；

【导师】 张雅绮；

【作者基本信息】 天津大学 ， 电路与系统， 2004， 硕士

【摘要】 信息化时代,通信网络是信息传递的重要媒介。传统通信网中,对语音、数据、图像、视频等多种业务分别采用不同特性的通信方式进行传输。然而随着社会的发展,单一特性的网络已无法满足信息化进程的需求,多元化的信息需要在同一网络中高速传递,由此提出了综合业务数字网ISDN的概念。如今以光纤为通信介质的宽带综合业务数字网B-ISDN已成为通信网络的主要发展方向,其核心技术异步转移模式ATM(Asynchronous Transfer Mode)具有能够动态分配信道频带,充分利用信道带宽,可适应从低速率到高速率的宽带业务要求等特点,能实现高速率、高吞吐率和高服务质量的信息交换,因此得到了广泛应用。ATM交换结构是实现ATM交换的关键技术之一。本文在深入研究ATM的基本理论、ATM交换结构、ATM交换结构控制机理及多级交换网络设计原理的基础上,提出一种基于Knockout交换结构、利用快速查表实现ATM交换的设计方法。该设计方法采用N2分离通路的模块化无阻塞互连结构,实现起来较简单且允许入线具有较高的传输速率。并利用该设计方法设计了一种基于快速查表算法的由VHDL描述的ATM交换单元。设计中使用快速查表,提高了查表效率,降低了对处理速度的要求。本文采用自顶向下(Top Down)的层次化设计方法,运用可综合的硬件描述语言VHDL对ATM交换单元中的各个功能模块分别进行描述,并利用EDA软件进行了功能仿真与逻辑综合,设计出了8×8的ATM交换单元,并可依据该交换单元设计出n×n的ATM交换单元及多级交换网。本设计采用的仿真设计环境是Modelsim 5.6,综合工具则采用Quartus II 3.0。这两款软件结合使用,可以对基于VHDL描述的数字系统进行设计输入、功能仿真、时序仿真及器件编程。本文通过对所设计的基于VHDL描述的ATM交换单元进行仿真验证可以得出如下结论:采用自顶向下的层次化设计、由VHDL描述的ATM交换单元能够实现信头变换、选路和排队三项基本功能;当多个信元同时竞争某一出端时能够对信元进行缓冲存储和排队输出;而且当有广播信元到来时还可以对所有出端进行广播输出。更多还原

【Abstract】 Information times, communication networks have become very important media for transferring information. In traditional communication mode, Voice, Data, Image and Video are transferred by communication networks with different transfer property. With the development of society, single characteristic network can’t satisfy the demand of modern communication, all kinds of information need speedily transporting in single network, therefore Integrated Services Digital Network (ISDN) is put forward. Now B-ISDN based on fiber has been the major trend. As a core transfer mode of B-ISDN, Asynchronous Transfer Mode (ATM) can dynamically allot and make the best of frequency band of channel, and fulfill high-speed, high-throughput and high-QoS information exchange. As a result, it is widely used.ATM switch fabric is one of the key technologies of realizing ATM switching. In this paper on the basis of thoroughly researching the basic principle of ATM, ATM switch fabric, the control principle of ATM switch fabric and design principle of multistage switching network, a design method that is based on Knockout switch fabric and makes use of lookup table to achieve ATM switching is brought forward. The method uses a N2 separate access, modularization and nonblocking interconnection frame. The frame is easily fulfilled, and its inputs have high transfer rate. ATM switch fabric based on the algorithm of speediness lookup table and VHDL is designed by this method. In this design lookup table is used, and improves the lookup efficiency and reduces the demand for the process rate. In this paper a hierarchical design method of Top Down is adopted, all of function blocks of ATM switch unit are described by synthesizable VHDL, and are functionally simulated and logically synthesized, so 8×8 ATM switch unit is obtained. According to this unit, n×n ATM switch unit and multistage switch network are also obtained. In this design Modelsim 5.6 is used as the simulation software, and synthesis software is Quartus II 3.0, by which the design entry, function simulation, timing simulation and device programming can be done. By simulating the switch unit, it can be seen that ATM switch unit that is designed by use of hierarchical design of top <WP=5>down with VHDL can perform the basic function of cell head changing, routing and queuing. If many cells race one output channel, the ATM switch can put these cells into a buffer, then queue and output them. When the broadcast cell advents, it can be delivered to all channels.更多还原