| Cognitive radio technology is an important part of the new generation broadband wireless mobile com-munication network,and also important technical features of the next generation mobile communication sys-tem. This technology takes chance to access to the authorized or unauthorized users frequency band under the premise without harmful interference,or with the method of public resource pool, can make multiple systems sharing spectrum, in order to improve spectrum efficiency.lt provides a strong technical support for solving the problem of insufficient spectrum resources and realizing the dynamic management as well as improving the spectrum utilization.At the present stage studies mainly focus on cognitive radio spectrum sensing,the physical layer transmission technology, radio resource management, network security and other aspects, including spectrum sensing is the basic support of the whole cognitive radio technology, the rest is done for quick and accurate spectrum detection. This thesis focused on this key technology and discussed in detail.Firstly,we review the research background and significance of cognitive radio technology, and introduces the popular direction of the research on cognitive radio, then introduce the derivation of spectrum sensing technology.This thesis has carried on the research of cognitive radio spectrum sensing method, are discussed from the point of view of cognitive radio spectrum to detect different aspects of the problem, given the challenges associated with spectrum sensing and introduces some early spectrum sensing technology such as energy detection, matched filtering detection, etc. The thesis explains the concept of collaborative detection as well as its different forms, the properties used for the detection of some wireless standards are presented.We discussed the DTMB digital television signal and the signal features as well as spectrum sensing algorithm for DTMB.Based on the characteristics of DTMB signal frame structure, we studied the use of the frame head of the PN sequence related PNAC and PNCC algorithm. And for the second frame head pattern of DTMB TV signal spectrum sensing method based on linear combination is presented.This algorithm can be not affected by the influence of the phase shift, at the same time detection performance is also improved.In the basis of existing collaborative spectrum detection algorithm based on matrix, we proposed based on fast Fourier transform blind spectrum detection algorithm. The algorithm eliminates the noise uncertain-ty,And compared with the matched filter algorithm and smooth loop detection algorithm, is a kind of blind detection algorithm, so there is no need to signal a priori information.and the performance is also better than energy detection algorithm.Because to avoid the eigenvalue decomposition calculation significantly reduces the computational complexity, it ensure the effective simple project implementation.In this chapter the algo-rithm steps are described in detail, and the theoretical value of decision threshold are derived.Based on the received signal covariance matrix, this thesis puts forward a goodness-of-fit algorithm, this algorithm can make full use of its eigenvalues of the covariance matrix, we improved the known AD algo-rithm, and the eigenvalues of the normalized processing, based on the random matrix theory, the cumulative probability density function s derived for the normalized chaotic characteristic value of random matrix. Sim- ulation results show that our proposed algorithm detection performance is better than that MME algorithm, and the signal with strong correlation detection algorithm performance is better than noise power known cases of energy detection. |
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