改革开放以来,我国电信网数字化技术飞速发展,尤其在光纤传输数字化和数字程控交换方面,取得了举世瞩目的成就.然而整个网路中,面广量大随处可见的市内电话用户环路依旧是有线模拟网.如何实现用户环路数字化,目前有两种技术方法.其一就是所谓窄带综合业务数字网N—ISDN,将数字化信号在电缆用户线上传输至终端设备.其二就是用微蜂窝无线技术实现市话用户环路的 Since the reform and opening up, the rapid development of China’s telecom network digital technology, especially in the digital transmission of optical fiber and digital program-controlled exchange, has made remarkable achievements. However, the entire network, a large number of large and widely visible local telephone user loop still Is a wired analog network.How to achieve the user loop digital, there are two technical methods.One is the so-called narrowband integrated services digital network N-ISDN, the digital signal in the cable subscriber line to the terminal equipment. The second is the use of micro Cellular wireless technology to achieve local users loop