通用移动通信系统的回顾

通用移动通信系统的回顾(中文2800字,英文2100字)
1.1 UMTS网络架构
欧洲/日本的3G标准，被称为UMTS。UMTS是一个在IMT-2000保护伞下的ITU-T批准的许多标准之一。随着美国的CDMA2000标准的发展，它是目前占主导地位的标准，特别是运营商将cdmaOne部署为他们的2G技术。在写这本书时，日本是在3G网络部署方面最先进的。三名现任运营商已经实施了三个不同的技术，J-PHONE使用UMTS，KDDI拥有CDMA2000网络，最大的运营商NTT DoCoMo正在使用品牌的FOMA（自由对媒体接入）系统。FOMA是基于原来的UMTS协议，而且更加的协调和标准化。
UMTS标准被定义为一个通过通用分组无线系统（GPRS）和全球演进的增强型数据技术（EDGE）的第二代GSM标准到UNTS标准的迁移。如图所示。这是一个广泛应用的基本原理，自2003年4月起，全球有超过847万GSM用户，占全球的移动用户数字的68%。重点是保持尽可能多的GSM网络与新系统的操作。
 
原文：
Review of UMTS
1.1 UMTS Network Architecture
The European/Japanese 3G standard is referred to as UMTS. UMTS is one of a number of standards ratified by the ITU-T under the umbrella of IMT-2000. It is currently the dominant standard, with the US CDMA2000 standard gaining ground, particularly with operators that have deployed cdmaOne as their 2G technology. At time of writing,Japan is the most advanced in terms of 3G network deployment. The three incumbent operators there have implemented three different technologies: J-Phone is using UMTS,KDDI has a CDMA2000 network, and the largest operator NTT DoCoMo is using a system branded as FOMA (Freedom of Multimedia Access). FOMA is based on the original UMTS proposal, prior to its harmonization and standardization.