【摘要】：高速發(fā)展的無線通信業(yè)務導致無線頻譜資源日益緊張,因此,具有高效頻譜資源利用率的新型無線通信技術一直是研究的熱點。作為高時間利用率無線通信技術的典型代表,認知無線電通過引入動態(tài)頻譜接入機制,有效的提高了頻譜利用率。頻譜可控的直擴通信技術不僅具有擴頻通信的優(yōu)勢,同時能夠生成具有零陷特征的頻譜,且該零陷特征可控,將其作為認知無線電的具體實現(xiàn)技術,可有效降低認知用戶頻譜接入時對于授權用戶的干擾,同時保證認知用戶自身的通信性能。通過兩者的結合,可構建一種新型的認知無線通信系統(tǒng)——頻譜可控的直擴認知通信系統(tǒng)。本文針對頻譜可控的直擴認知通信系統(tǒng)關鍵技術進行研究,并結合壓縮感知理論在認知無線電和擴頻通信中的應用,做了如下的研究工作:(1)對于認知無線電的寬帶頻譜感知,基于壓縮感知理論的壓縮寬帶頻譜感知方法是解決系統(tǒng)前端高采樣率需求問題的有效方案。而在壓縮寬帶頻譜感知中,對于頻譜稀疏度的依賴阻礙了該技術在實際中的廣泛應用,針對該問題,提出一種稀疏度自適應的壓縮采樣匹配追蹤算法(SACoSaMP),并給出該算法能夠精確重構稀疏信號的理論分析。所提算法不依賴于信號真實稀疏度,且具有較好的重構效果,將其應用于壓縮寬帶頻譜感知中,能有效實現(xiàn)稀疏度未知情況下的頻譜檢測。(2)為了獲得頻譜可控的擴頻序列,借鑒mW復合序列思路,分別提出基于譜零陷碼的頻譜可控復合序列和基于塊編碼的頻譜可控復合序列,推導復合序列功率譜表達式,分析其頻譜可控性及頻譜特征與序列參數(shù)、序列復合方式的對應關系,給出所需頻譜形狀的設計方法,分析比較各復合序列的特性。構建直擴認知通信系統(tǒng),采用所提出的復合序列實現(xiàn)認知用戶的頻譜接入,分析系統(tǒng)中授權用戶和認知用戶的誤碼率性能。(3)針對mW復合序列的參數(shù)估計問題,分別提出采用其頻譜和循環(huán)譜來實現(xiàn)參數(shù)的估計。為了降低頻譜獲取所需采樣率,采用調制寬帶轉換(MWC)來重構信號頻譜,通過檢測頻譜峰值來實現(xiàn)mW復合序列中Walsh序列序號及信號載頻的估計。為了提升估計性能,推導mW復合序列的循環(huán)譜表達式,給出循環(huán)譜切面峰值位置與復合序列參數(shù)的對應關系。針對mW復合序列循環(huán)譜獲取所需采樣率高的問題,采用壓縮循環(huán)譜理論重構信號循環(huán)譜,并通過檢測循環(huán)譜切面峰值來實現(xiàn)mW復合序列中Walsh序列序號、m序列碼片速率和信號載頻的估計。(4)為了利用復合序列所具有的特征來提升擴頻接收機的性能,介紹一種新型的壓縮擴頻接收機。該接收機從擴頻信號所具有的稀疏性角度出發(fā),通過壓縮感知理論來實現(xiàn)擴頻信號的接收,結構極其簡單,但誤碼率性能較傳統(tǒng)的相關接收機有所下降。在復合序列參數(shù)估計方法研究的基礎上,提出基于支撐集估計的壓縮擴頻接收機,該接收機首先通過對接收信號的參數(shù)估計獲得待重構信號的支撐集,然后利用估計的支撐集來提升壓縮擴頻接收機的誤碼率性能。
[Abstract]:With the rapid development of wireless communication services, wireless spectrum resources are increasingly scarce. Therefore, new wireless communication technologies with high efficiency of spectrum resource utilization have been the focus of research. Utilization rate. Spectrum-controllable DS/SS communication technology not only has the advantage of spread spectrum communication, but also can generate spectrum with zero-pitch feature, and the zero-pitch feature is controllable. As a specific implementation technology of cognitive radio, it can effectively reduce the interference of cognitive users to authorized users when spectrum access, while ensuring the cognitive users themselves. Communication performance. A new cognitive wireless communication system, spectrum-controllable DSSS cognitive communication system, can be constructed by combining the two. In this paper, the key technologies of spectrum-controllable DSSS cognitive communication system are studied, and the application of compressed sensing theory in cognitive radio and spread spectrum communication is studied as follows. Work: (1) Compressed broadband spectrum sensing based on compressed sensing theory is an effective solution to the problem of high sampling rate in front of the system for cognitive radio. A sparsity adaptive compression sampling matching pursuit algorithm (SACoSaMP) is proposed and the theoretical analysis of the algorithm is given. The proposed algorithm does not depend on the true sparsity of the signal, and has a good reconstruction effect. It can be applied to compressed broadband spectrum sensing to effectively realize sparsity unknown. (2) In order to obtain a spectrum-controllable spread spectrum sequence, a spectrum-controllable composite sequence based on spectrum null-notch code and a spectrum-controllable composite sequence based on block coding are proposed, respectively. The power spectrum expression of the composite sequence is deduced, and its spectrum controllability, spectrum characteristics and sequence parameters are analyzed. According to the corresponding relationship, the design method of spectrum shape is given, and the characteristics of each complex sequence are analyzed and compared. A DS-SS cognitive communication system is constructed. The spectrum access of cognitive users is realized by using the proposed complex sequence. The BER performance of authorized users and cognitive users in the system is analyzed. (3) For the problem of parameter estimation of mW composite sequence, the system is divided into two parts. In order to reduce the sampling rate needed for spectrum acquisition, the modulation broadband conversion (MWC) is used to reconstruct the signal spectrum, and the Walsh sequence number and the carrier frequency of the signal are estimated by detecting the peak value of the spectrum. To solve the problem of high sampling rate in obtaining cyclic spectrum of mW composite sequence, the cyclic spectrum of signal is reconstructed by compressed cyclic spectrum theory, and the sequence number, chip rate and sum of Walsh sequences in mW composite sequence are realized by detecting the peak value of cyclic spectrum section. (4) In order to improve the performance of spread spectrum receiver by utilizing the characteristics of composite sequence, a new compressed spread spectrum receiver is introduced. The receiver is based on the sparsity of spread spectrum signal and the theory of compressed sensing. The structure of the receiver is very simple, but the BER performance is very good. Compressed spread spectrum receiver based on support set estimation is proposed. The support set of the reconstructed signal is obtained by estimating the parameters of the received signal, and then the error of the compressed spread spectrum receiver is improved by using the estimated support set. Rate performance.
【學位授予單位】：哈爾濱工程大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TN914.42;TN925

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