基于循环平稳特征的频谱感知技术研究

发布时间：2018-06-20 10:18

本文选题：认知无线电 + 频谱感知　；参考：《华中科技大学》2014年博士论文

【摘要】：在过去的几十年,无线通信技术飞速发展,涌现出越来越多的新技术,同时对频谱资源的需求也越来越高。随着频谱资源的短缺状况越来越明显,认知无线电技术越来越受到人们的关注。通过允许认知无线电用户租用授权用户的频谱资源,或者授权用户将其频谱资源共享给认知无线电用户使用,认知无线电技术将大大提高频谱的利用效率。在认知无线电技术中,关键技术之一是频谱感知技术。本论文研究如何利用循环平稳特征进行授权用户信号检测,其主要贡献如下： (1)由于具备恒虚警率性质以及低信噪比状况下仍保持较好的检测性能,Dandawate-Giannakis算法在许多循环平稳频谱感知方法中得到广泛的应用。这是一种广义似然比检验算法,其假定循环自相关估计的分布在无效假设和备择假设上具有相同的渐近协方差。事实上,本论文通过研究揭示：在频谱感知领域这样的假设并不完全正确。本文推导了在频谱感知中的广义似然比检验统计量,并给出其渐近分布,证明其依然具备恒虚警率的特性。仿真结果表明,本文提出的广义似然比算法在检测性能上优于Dandawate-Giannakis算法。 (2)本文将所提出的广义似然比检验算法扩展到多天线频谱感知。通过将各个天线自身的循环自相关以及任意一对天线间的循环互相关纳入检验算法,使其检验性能较单天线环境有明显提高。仿真结果证实了该方法的有效性。本文还将多天线广义似然比算法和直接多天线扩展Dandawate-Giannakis算法进行了对比,验证了本文所提方法的优势。 (3)大部分通信调制信号(如BPSK、QPSK)的循环自相关在正负循环频率上是共轭的,由于它们在实际的通信环境中所受到的噪声和多径衰落影响一般相互独立,因此可以将这一特性运用于频谱感知以提高检验性能。本文给出了多径衰落情况下双循环频率的循环自相关函数,并将Dandawate-Giannakis算法扩展到双循环频率循环平稳特征频谱感知中,以获得频率分集效果。仿真结果表明,本文提出的方法较单频率循环平稳频谱感知性能有明显提高。 (4)本文提出了一种在正交频分复用信号中采用跳频子载波的循环平稳特征签名方法,在频率选择性衰落信道中具有高可检测性,并具备很低的开销。
[Abstract]:In the past few decades, wireless communication technology has developed rapidly, and more and more new technologies have emerged. At the same time, the demand for spectrum resources is becoming more and more high. As the shortage of spectrum resources becomes more and more obvious, cognitive radio technology is getting more and more attention. By allowing users to rent the spectrum resources of authorized users. Source, or authorizing users to share their spectrum resources to cognitive radio users, cognitive radio technology will greatly improve the efficiency of spectrum utilization. In cognitive radio technology, one of the key technologies is spectrum sensing technology. This paper studies how to use cyclostationary features to carry out authorized user signal detection, the main contributions of this paper are as follows: Below:
(1) the Dandawate-Giannakis algorithm has been widely used in many cyclostationary spectrum sensing methods because of the constant false alarm rate and good detection performance under low SNR conditions. This is a generalized likelihood ratio test algorithm, which assumes that the distribution of the cyclic autocorrelation estimator is on the invalid hypothesis and the alternative hypothesis. The same asymptotic covariance. In fact, this paper reveals that the hypothesis in the domain of spectrum sensing is not completely correct. This paper derives the generalized likelihood ratio test statistics in spectrum sensing, and gives its asymptotic distribution, proving that it still possesses the characteristic of constant false alarm rate. The simulation results show that the generalized similarity of this paper is shown in this paper. The algorithm is superior to the Dandawate-Giannakis algorithm in terms of detection performance.
(2) this paper extends the proposed generalized likelihood ratio test algorithm to multi antenna spectrum sensing. By incorporating the cyclic autocorrelation of each antenna itself and the cyclic cross correlation of any pair of antennas into the test algorithm, the test performance is significantly higher than that of the single antenna environment. The simulation results confirm the effectiveness of the method. This paper will also prove the validity of the method. The multi antenna generalized likelihood ratio algorithm is compared with the direct multi antenna extended Dandawate-Giannakis algorithm, which verifies the advantages of the proposed method.
(3) the cyclic autocorrelation of most communication modulation signals (such as BPSK, QPSK) is conjugated on the positive and negative cycle frequency. Because of their noise and multipath fading in the actual communication environment, they are generally independent. Therefore, this characteristic can be applied to spectrum sensing to improve the performance of the test. This paper gives the multipath fading situation. The cyclic autocorrelation function of the lower double cycle frequency and the Dandawate-Giannakis algorithm are extended to the frequency spectrum sensing of the double loop frequency cyclostationary feature to obtain the frequency diversity effect. The simulation results show that the proposed method is better than the stationary frequency spectrum sensing performance of the single frequency cycle.
(4) this paper proposes a cyclostationary signature scheme using frequency hopping subcarriers in orthogonal frequency division multiplexing (fwdm) signals, which has high detectability in frequency selective fading channels and has very low overhead.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN925

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