Abstract: Recently, demand for high-speed Internet access is rapidly increasing and a lot of people enjoy broadband wired Internet access services using ADSL ( Asymmetric Digital Subscriber Line) or cable modems at home. On the other hand , the cellular phone is getting very popular and users enjoy its location-free and wire-free services. The cellular phone also enables people to connect their laptop computers to the Internet in location-free and wire-free manners. However , present cellular systems like GSM (Global System for Mobile communications) can provide much lower data rates compared with those provided by the wired access systems, over a few Mbps(Mega bit per second).Even in the next generation cellular system, UMTS ( Universal Mobile Telecommunications System), the maximum data rate of its initial service is limited up to 384kbps; therefore even UMTS cannot satisfy users’ expectation of high-speed wireless Internet access.
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