一、前言 随着信息高速公路的迅速发展,如何为用户提供宽带业务的问题显得越来越突出。发达国家对宽带接入技术的研究特别重视,提出了许多方法,但目前都还存在各种问题,远未成熟。 诸多宽带接入技术提供者主要分为两大类,一类是LECs(Local Exchange Carriers)市话交换通信公司,希望能利用双绞线用户环来提供宽带业务,但有许多技术难关。另一类是经营有线电视系统的公司MSOs(Multiple SystemOperators),希望在传送电视信号的同时提供宽带综合业务。 I. Introduction With the rapid development of information superhighway, how to provide broadband services to users becomes more and more prominent. The developed countries pay special attention to the research of broadband access technology and put forward many methods. However, there are still various problems that are far from being mature. Many broadband access technology providers are mainly divided into two categories, one is LECs (Local Exchange Carriers) local exchange carriers, hoping to use twisted pair subscriber ring to provide broadband services, but there are many technical difficulties. The other is the MSOs (Multiple System Operators), a company that operates cable television systems, hoping to provide broadband integrated services while transmitting television signals.