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一、系统概述UMTS(Universal MobileTelecommunication Sys-tems,通用移动通信系统)是采用WCDMA空中接口的第三代移动通信系统,标准由3GPP具体定义。WCDMA可以采用FDD与TDD模式,其3GPP版本分为R99、R4和R5版。R99于2000年6月版本基本稳定,9月份版本比较成熟、完善,其Iu、Iub、Iur接口均采用ATM和IP方式,网络是以ATM交换为核心的网络,电路与分组交换节点逻辑上分开。R4、R5提出了基于IP的核心网结
First, the system overview UMTS (Universal Mobile Telecommunication Sys-tems, Universal Mobile Telecommunications System) is the third generation mobile communication system using WCDMA air interface, the standard defined by the 3GPP. WCDMA can adopt FDD and TDD mode, its 3GPP edition is divided into R99, R4 and R5 edition. R99 in June 2000 version of the basic stability of the September version of the more mature and perfect, its Iu, Iub, Iur interfaces are used ATM and IP, the network is based on ATM switching network, the circuit and packet switching nodes logically separate . R4, R5 proposed based on IP core network node