OFDM信号频谱感知技术的研究与硬件实现

发布时间：2018-03-28 02:14

本文选题：频谱感知　切入点：OFDM　出处：《哈尔滨工业大学》2014年硕士论文

【摘要】：无线通信技术在近几年发展非常迅速,因此对频谱的利用造成了拥塞的现象,而另一方面,授权频谱的使用率却非常低,传统的静态频谱分配机制导致的频谱使用率不均匀与日益增长的频谱需求之间的矛盾日益显著。认知无线电的概念就在这样的背景下被提出,认知无线电技术被认为是解决目前频谱资源紧张的一个有效而且可行的手段,它的的核心思想是感知空闲的频段加以利用,同时实时监测该频段,如果有授权用户进入则立即释放,从而提高频谱利用率,频谱感知技术是实现这一目标的关键技术。目前常见的频谱感知传统算法有:匹配滤波器检测法、能量检测法、循环平稳特性检测法等。正交频分复用技术,近几年逐渐受到关注,越来越多的应用在很多场合,比如数字电视、音频广播、无线网络和宽带网络,而且,OFDM技术将会成为未来宽带无线通信系统的关键技术,所以对OFDM的频谱感知就变得格外重要。本文选用算法是自相关系数检测法(Cyclic Prefix Correlation Coefficient,CPCC),自相关系数检测法是利用OFDM信号的循环前缀的相关性原理来进行检测的,在单径信道条件下,由对接收信号的协方差矩阵的估计推导出自相关系数的估计值,在虚警概率为0.05条件下,matlab仿真得出检测概率与信噪比的关系,然后,完成CPCC算法的FPGA设计与实现,主要在Quartus II开发平台上使用verilog硬件描述语言完成各个模块的设计,用Modelsim对每个模块进行仿真,最后,将程序下载到FPGA开发板并运行,利用Signal Tap II进行实时获取FPGA运行时的内部信号,就完成了CPCC算法的硬件实现,构成CPCC算法需要的模块包括ROM模块、乘法器模块、控制模块、加法模块和检测模块。所使用的OFDM基带信号由matlab产生。并在不同信噪比情况下进行多次测试,得出与理论基本一致的结果。通过对CPCC算法的分析得出,CPCC算法在只有噪声情况下,相关很小,但在频段被使用的情况下,相关性非常大。CPCC算法是一个简单并且计算高效的OFDM信号频谱感知方法。
[Abstract]:Wireless communication technology has developed very rapidly in recent years, so the use of spectrum has caused congestion. On the other hand, the use of authorized spectrum is very low. The contradiction between the uneven spectrum utilization caused by the traditional static spectrum allocation mechanism and the growing spectrum demand is increasingly obvious. The concept of cognitive radio is proposed in this context. Cognitive radio technology is considered to be an effective and feasible means to solve the current spectrum resource shortage. The core idea of cognitive radio is to use the idle frequency band and monitor the frequency band in real time. If an authorized user enters it, it can be released immediately to improve the spectrum efficiency. Spectrum sensing technology is the key technology to achieve this goal. At present, the traditional spectrum sensing algorithms are: matched filter detection method, energy detection method, The orthogonal Frequency Division Multiplexing (OFDM) technology has attracted more and more attention in recent years. More and more applications have been used in many fields, such as digital television, audio broadcasting, wireless network and broadband network. Moreover, OFDM technology will become the key technology of broadband wireless communication system in the future. Therefore, spectrum sensing of OFDM becomes more and more important. In this paper, the algorithm is cyclic Prefix Correlation coefficient detection, and autocorrelation coefficient detection is based on the correlation principle of cyclic prefix of OFDM signal. Under the condition of single path channel, the detection method of autocorrelation coefficient is based on the correlation principle of cyclic prefix of OFDM signal. The estimation of covariance matrix of received signal is derived from the estimated value of correlation coefficient. Under the condition of false alarm probability 0. 05, the relationship between detection probability and SNR is obtained by simulation in MATLAB. Then, the FPGA design and implementation of CPCC algorithm are completed. Mainly in the Quartus II development platform using verilog hardware description language to complete the design of each module, using Modelsim to simulate each module, finally, the program is downloaded to the FPGA development board and run. Using Signal Tap II to acquire the internal signal of FPGA runtime in real time, the hardware implementation of CPCC algorithm is completed. The modules that constitute CPCC algorithm include ROM module, multiplier module and control module. Addition module and detection module. The OFDM baseband signal used is generated by matlab, and has been tested many times under different SNR, and the results are basically consistent with the theory. Through the analysis of CPCC algorithm, it is found that the CPCC algorithm is only noisy. The correlation is very small, but when the frequency band is used, the correlation is very large. CPCC algorithm is a simple and efficient spectrum sensing method for OFDM signals.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.53

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