Sunday, April 18, 2010

many technical problems

Nowadays, with the fast growth of high data transmission service such as broad band Internet and multimedia,the demands for high speed wireless access have been rapidly increasing. Due to the bad environment in wireless communication, there are many technical problems in broad band communication. Aiming at the limited wireless frequency discount wedding dresses resource, it is one of technical problems to fully improve usage efficiency. As a smart spectrum sharing technology, cognitive radio can sense the wireless communications environment with the lace wedding dresses support of artificial intelligence; changing system parameters automatically according to certain learning and decision making algorithms; testing idle spectrums dynamically and make cheap wedding gown dresses efficiently use of them. Theoretically, it allows spectrum to multiplex and share in time, space and frequency domain. Spectrum sensing is one of the bases of cheap evening dresses constructing a cognitive radio system. Collecting statistical information about wireless environment can not only provide assistance for higher level spectrum management but also some data to support the power control of the custom made prom dresses system. Cooperative diversity is one of the effective methods to sense spectrum, which can improve agility and reduce detection time. Cooperative detection can restrain multipath fading and shadow effect to a great extent, also it can improve the detection efficiency even in sever shadow environment.
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