Research On Spectrum Sensing Technique Based On Wavelet

With the rapid development of wireless communication, a shortage of spectrum availability at frequencies revealed. Cognitive radio is an attractive way to deal with the issue of the spectrum scarcity. Spectrum sensing plays a key role in the Cognitive radio system. The key ideas of CR technique are as follows:an unlicensed user to discover a vacant spectrum for spectrum access under the avoid causing interference to primary users, to improve spectral efficiency. The spectrum sensing as the key technology of CR system must be able to detect the vacant spectrum as quickly and accurately for the use of CR users. This dissertation presents spectrum sensing based on wavelet, which is a new kind of spectrum sensing technology. It has the characteristics of flexible multi-resolution for the spectrum sensing.Firstly, this dissertation introduces the available digital TV channel. The detection model is proposed in this dissertation is wavelet channel scanning detection with wavelet fine spectrum detection, which is used to detect the OFDM based digital television signals. Taking the advantages of the multi-resolution characteristics of wavelet, entire expected frequency band is scanned at first, and a smoothing progressing optimization algorithm for reducing the false alarm probability is performed to estimate the values of both carrier frequency and bandwidth of signals. Improve the frequency resolution to estimate the number of the subcarriers of the signals at the fine detection. The result is compared with the frequency domain energy detection. Proposed AND and OR decision which can be chosen according to the detection requirements.The simulation results show that the proposed algorithm is adaptive to spectrum sensing in cognitive radio systems, which can according to the needing for quick scanning detection or fine detection. In order to determine if there are primary users in the expect frequency.