一、概述1.定义与建议 为了适应新业务的发展,近几年各种用户环路新技术的开发和应用特别活跃,复用设备、数字交叉连接设备、无线用户环路和光用户环路等技术的引入,使得用户网的功能和能力得到了很大扩展,逐渐突破了传统用户线路网的概念。为此国际电联标准部(ITU-T)根据近年来的发展演变趋势,提出了用户接入网(AccessNetwork,AN)的概念,并提出了一系列的建议。定义接入网(AN)为;本地交换机与用户端设备之间的实施系统,它可部分或全部代替传统的本地线路网,可含复用、交叉连接和传输功能。由此可见,接入网的组织形式在通信发展的不同阶段是 I. Overview 1. Definition and Suggestion In order to adapt to the development of new services, the development and application of new technologies for various subscriber loops have been particularly active in recent years. Multiplexing equipment, digital cross-connect equipment, wireless subscriber loops, and optical subscriber loops With the introduction of technology, the functions and capabilities of user networks have been greatly expanded, gradually breaking the concept of traditional subscriber line networks. To this end, the ITU Telecommunication Standardization Department (ITU-T) has put forward the concept of Access Network (AN) based on the evolution in recent years and put forward a series of suggestions. Definition An access network (AN) is an implementation system between a local switch and a client device that partially or fully replaces the traditional home network with multiplexing, cross-connect and transport functions. Thus, the form of access network at different stages of the development of communications is