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.