毕业设计论文英文原文.docVIP

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毕业设计(论文)英文翻译原文 院 (系): 信息与通信学院 专 业: 电子信息工程 学生姓名: 张 晨 学 号: 030220606 指导教师: 田克纯 职 称: 高级工程师 2007年 6 月 6 日 UMTS   For effective, efficient communications, standardization is critical, and nowhere is this more evident than in the areas of mobile computing and cellular telephony.   If you need data access or e-mail through your cell phone, you’re likely to be using one of two different technologies: Code Division Multiple Access (CDMA) or Global Service of Mobile Communication (GSM).   Both CDMA and GSM are second-generation (2G) technologies, and they have co-existed for several years. Each technology has its supporters. CDMA phones are engineered specifically for an individual carrier, whereas GSM phones make use of a removable memory card called the Subscriber Identity Module (SIM). A SIM card contains all the key information required to activate a phone, including the user’s telephone number, personal identification number, address book and encoded network identification details. A user can easily move a SIM from one phone to another.   Though GSM phones are interoperable with one another, different countries use different parts of the frequency spectrum, so “world phones” typically must be capable of using several frequencies.   Today, the fastest-growing use of cellular networks is for the transmission of all kinds of data and rich media, including Web sites, video, music, images, and maps and driving directions. The older 2G networks simply couldn’t handle that volume of traffic, and they couldn’t offer the speed needed for transmitting large files. The answer was to make the services faster and build out the networks to deal with more traffic.   Here, too, the CDMA and GSM paths continued their separate but parallel development. CDMA brought us CDMA2000 and 1xRTT networks. The most recent developments are 1x Evolution Data Optimized, or EV-DO, and 1x Evolution Data/Voice,

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