本文選題：頻譜感知　切入點：OFDM　出處：《哈爾濱工業(yè)大學(xué)》2014年碩士論文

【摘要】：無線通信技術(shù)在近幾年發(fā)展非常迅速,因此對頻譜的利用造成了擁塞的現(xiàn)象,而另一方面,授權(quán)頻譜的使用率卻非常低,傳統(tǒng)的靜態(tài)頻譜分配機制導(dǎo)致的頻譜使用率不均勻與日益增長的頻譜需求之間的矛盾日益顯著。認知無線電的概念就在這樣的背景下被提出,認知無線電技術(shù)被認為是解決目前頻譜資源緊張的一個有效而且可行的手段,它的的核心思想是感知空閑的頻段加以利用,同時實時監(jiān)測該頻段,如果有授權(quán)用戶進入則立即釋放,從而提高頻譜利用率,頻譜感知技術(shù)是實現(xiàn)這一目標的關(guān)鍵技術(shù)。目前常見的頻譜感知傳統(tǒng)算法有:匹配濾波器檢測法、能量檢測法、循環(huán)平穩(wěn)特性檢測法等。正交頻分復(fù)用技術(shù),近幾年逐漸受到關(guān)注,越來越多的應(yīng)用在很多場合,比如數(shù)字電視、音頻廣播、無線網(wǎng)絡(luò)和寬帶網(wǎng)絡(luò),而且,OFDM技術(shù)將會成為未來寬帶無線通信系統(tǒng)的關(guān)鍵技術(shù),所以對OFDM的頻譜感知就變得格外重要。本文選用算法是自相關(guān)系數(shù)檢測法(Cyclic Prefix Correlation Coefficient,CPCC),自相關(guān)系數(shù)檢測法是利用OFDM信號的循環(huán)前綴的相關(guān)性原理來進行檢測的,在單徑信道條件下,由對接收信號的協(xié)方差矩陣的估計推導(dǎo)出自相關(guān)系數(shù)的估計值,在虛警概率為0.05條件下,matlab仿真得出檢測概率與信噪比的關(guān)系,然后,完成CPCC算法的FPGA設(shè)計與實現(xiàn),主要在Quartus II開發(fā)平臺上使用verilog硬件描述語言完成各個模塊的設(shè)計,用Modelsim對每個模塊進行仿真,最后,將程序下載到FPGA開發(fā)板并運行,利用Signal Tap II進行實時獲取FPGA運行時的內(nèi)部信號,就完成了CPCC算法的硬件實現(xiàn),構(gòu)成CPCC算法需要的模塊包括ROM模塊、乘法器模塊、控制模塊、加法模塊和檢測模塊。所使用的OFDM基帶信號由matlab產(chǎn)生。并在不同信噪比情況下進行多次測試,得出與理論基本一致的結(jié)果。通過對CPCC算法的分析得出,CPCC算法在只有噪聲情況下,相關(guān)很小,但在頻段被使用的情況下,相關(guān)性非常大。CPCC算法是一個簡單并且計算高效的OFDM信號頻譜感知方法。
[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.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN929.53

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