频谱可控的直扩认知通信系统关键技术研究

发布时间：2018-08-23 21:23

【摘要】：高速发展的无线通信业务导致无线频谱资源日益紧张,因此,具有高效频谱资源利用率的新型无线通信技术一直是研究的热点。作为高时间利用率无线通信技术的典型代表,认知无线电通过引入动态频谱接入机制,有效的提高了频谱利用率。频谱可控的直扩通信技术不仅具有扩频通信的优势,同时能够生成具有零陷特征的频谱,且该零陷特征可控,将其作为认知无线电的具体实现技术,可有效降低认知用户频谱接入时对于授权用户的干扰,同时保证认知用户自身的通信性能。通过两者的结合,可构建一种新型的认知无线通信系统——频谱可控的直扩认知通信系统。本文针对频谱可控的直扩认知通信系统关键技术进行研究,并结合压缩感知理论在认知无线电和扩频通信中的应用,做了如下的研究工作:(1)对于认知无线电的宽带频谱感知,基于压缩感知理论的压缩宽带频谱感知方法是解决系统前端高采样率需求问题的有效方案。而在压缩宽带频谱感知中,对于频谱稀疏度的依赖阻碍了该技术在实际中的广泛应用,针对该问题,提出一种稀疏度自适应的压缩采样匹配追踪算法(SACoSaMP),并给出该算法能够精确重构稀疏信号的理论分析。所提算法不依赖于信号真实稀疏度,且具有较好的重构效果,将其应用于压缩宽带频谱感知中,能有效实现稀疏度未知情况下的频谱检测。(2)为了获得频谱可控的扩频序列,借鉴mW复合序列思路,分别提出基于谱零陷码的频谱可控复合序列和基于块编码的频谱可控复合序列,推导复合序列功率谱表达式,分析其频谱可控性及频谱特征与序列参数、序列复合方式的对应关系,给出所需频谱形状的设计方法,分析比较各复合序列的特性。构建直扩认知通信系统,采用所提出的复合序列实现认知用户的频谱接入,分析系统中授权用户和认知用户的误码率性能。(3)针对mW复合序列的参数估计问题,分别提出采用其频谱和循环谱来实现参数的估计。为了降低频谱获取所需采样率,采用调制宽带转换(MWC)来重构信号频谱,通过检测频谱峰值来实现mW复合序列中Walsh序列序号及信号载频的估计。为了提升估计性能,推导mW复合序列的循环谱表达式,给出循环谱切面峰值位置与复合序列参数的对应关系。针对mW复合序列循环谱获取所需采样率高的问题,采用压缩循环谱理论重构信号循环谱,并通过检测循环谱切面峰值来实现mW复合序列中Walsh序列序号、m序列码片速率和信号载频的估计。(4)为了利用复合序列所具有的特征来提升扩频接收机的性能,介绍一种新型的压缩扩频接收机。该接收机从扩频信号所具有的稀疏性角度出发,通过压缩感知理论来实现扩频信号的接收,结构极其简单,但误码率性能较传统的相关接收机有所下降。在复合序列参数估计方法研究的基础上,提出基于支撑集估计的压缩扩频接收机,该接收机首先通过对接收信号的参数估计获得待重构信号的支撑集,然后利用估计的支撑集来提升压缩扩频接收机的误码率性能。
[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.
【学位授予单位】：哈尔滨工程大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN914.42;TN925

【相似文献】