3G网络的介绍（专业英语）

Various systems were developed and used around the world for first-generation analog mobile communications, and three systems now coexist for second-generation digital communications (PDC in Japan, GSM in Europe and TIA standards in the US). The global standard for third-generation wireless communications has been determined by the International Telecommunication Union (ITU) under the integrated name of IMT-2000. IMT-2000 realizes mobile communications systems that offer high quality equivalent to that of fixed networks under global standard radio interfaces and can provide a wide range of services. In addition to making it possible to easily communicate with anybody, anywhere and anytime on a global scale, it also permits high-speed, large-volume data communications and image transmissions.NTT DoCoMo has been active in research and development activities relating to IMT-2000, and the W-CDMA (wideband code-division multiple access) radio interface that NTT DoCoMo has been promoting is included in IMT-2000.Now in 2001, NTT DoCoMo has launched FOMA, which is the first service in the world based on IMT-2000. FOMA realizes clearer and more comfortable communications environments than ever before and provides a new mobile environment where voice, still images and video are freely handled through the introduction of new technologies. These include large-volume communications using broad frequency bands and intelligent networks that can select the optimal communications rates and paths according to the type and volume of information being transmitted