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Today's wireless networks are characterized by a fixed spectrum assignment policy. However, a large portion of the assigned spectrum is utilized from 15% to 85% with a high variance in time. Cognitive radio can improved the spectrum efficient through dynamic spectrum access. In this paper, a scheme is proposed in which cognitive radio networks (CRN)(More)
In this paper, a coarse synchronization scheme is proposed through introducing a digital matched filter combining diversity according to the same time hopping (TH) as the expected user in ultra wideband (UWB) communications. By analyzing the signal characteristic, the filter window parameters are set to utilize sufficient energy from the receiving signal in(More)
To cope with the interference between UWB system and traditional narrow band wireless systems, CR (Cognitive Ratio) technology is introduced into UWB. The CUWB (Cognitive UWB) system realized by IR needs to generate sending pulse waveform whose spectrum can be adapted to the changing spectrum environment. In this paper, a CUWB pulse design method based on(More)
Cognitive radio technology uses the ability of dynamic spectrum access to solve the problem of spectrum efficiency, but considered the view of application, the designs depended cognitive radio technology face the hardware restriction, and the cost is too expensive. Therefore the spectrum auction mechanism referenced to economic theory has a high value of(More)
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