外文翻译蜂窝无线通信系统研究.docxVIP

附录Ⅰ 外文翻译(原文) RESEARCH OF CELLULAR WIRELESS COMMUNATION SYSTEM Abstract 1897, Marconi demonstrates the first practical application of the mobile radio communication, opening up a precedent of mobile communication, wireless communication in the modern sense was born. From that day onwards, the wireless communication technology is committed to achieving better communication quality, lower power consumption, smaller size and cheaper price. In the next 60 years, a number of landmark technological breakthroughs to promote the further development of mobile communications. Know the early 1980s, with the establishment of a cellular mobile communication systems, mobile communication system has now entered a period of prosperity and development. The cellular system has experienced rapid exponential growth, clearly showing that wireless communication has a bright future.Cellular communication systems allow a large number of mobile users to seamlessly and simultaneously communicate to wireless modems at fixed base stations using a limited amount of radio frequency (RF) spectrum. The RF transmissions received at the base stations from each mobile are translated to baseband, or to a wideband microwave link, and relayed to mobile switching centers (MSC), which connect the mobile transmissions with the Public Switched Telephone Network (PSTN). Similarly, communications from the PSTN are sent to the base station, where they are transmitted to the mobile. Cellular systems employ either frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), or spatial division multiple access (SDMA). 1 Introduction A wide variety of wireless communication systems have been developed to provide access to the communications infrastructure for mobile or fixed users in a myriad of operating environments. Cellular mobile communication system by the exchange of Network Subsystem (NSS), the wireless base station subsystem (BSS) and mobile station