MULTI-STAGES CO-OPERATIVE/NONCOOPERATIVE SCHEMES OF SPECTRUM SENSING FOR COGNITIVE RADIO SYSTEMS

Searching for spectrum holes in practical wireless channels where primary users experience multipath fading and shadowing, with noise uncertainty, limits the detection performance significantly. Moreover, the detection challenge will be tougher when different band types have to be sensed, with different signal and spectral characteristics, and probably overlapping spectra. Besides, primary user waveforms can be known (completely or partially) or unknown to allow or forbid cognitive radios to use specific kinds of detection schemes! Hidden primary user’s problem, and doubly selective channel oblige the use of cooperative sensing to exploit the spatial diversity in the observations of spatially located cognitive radio users. Incorporated all the aforementioned practical challenges as a whole, this paper developed a new multistage detection scheme that intelligently decides the detection algorithm based on power, noise, bandwidth and knowledge of the signal of interest. The proposed scheme switches between individual and cooperative sensing and among featured based sensing techniques (cyclo-stationary detection and matched filter) and sub-band energy detection according to the characteristics of signal and band of interest.Compared to the existing schemes, performance evaluations show reliable results in terms of probabilities of detection and mean sensing times under the aforementioned conditions