【作者】 郑瑜；

【导师】 何世彪；

【作者基本信息】 重庆大学 ， 通信与信息系统， 2010， 硕士

【摘要】 作为一种认知无线电(Cognitive Radio,CR)技术的收发信机候选方案,变换域通信系统(Transform Domain Communication System, TDCS)能够通过频谱估计与标记主动避开干扰,在变换域完成TDCS信号的设计,以此适应快速变化的无线通信环境;生成的伪随机相位矢量可以为TDCS系统各频谱分量信号提供伪随机相位,使其具有类似噪声的低截获(Low Probability of Intercept,LPI)特性;与此同时,基于变换域设计的基函数可以实现TDCS系统码分多址通信,使其具有较强的抗干扰通信能力。TDCS的提出为解决不断增长的无线通信应用需求与日益紧张的无线频谱资源之间的矛盾提供了一种有效的途径。首先,对常用的TDCS频谱估计方法进行了研究分析,基于TDCS信号的特点设计了一种TDCS空间电磁频谱环境模拟仿真模型,并通过Matlab进行了建模、仿真和分析评估。其次,在介绍TDCS伪随机相位矢量和基函数生成基本原理的基础之上,完成了对其特性的分析,并由此展开了对TDCS系统参数选择、系统多址能力以及基函数在用户数据调制中的应用探讨和研究,给出了最小公倍数相位映射和等间隔相位映射两种有效的、适合TDCS系统多址通信基函数生成的基本方法,并通过Matlab进行了仿真分析。最后,在介绍TDCS信号同步检测方法和数据相关接收方法的基础之上,完成了对TDCS系统的阻塞干扰和跳频干扰信号及其特性的分析,给出了TDCS阻塞干扰信号和跳频干扰信号产生模型,并从数学模型的角度,对TDCS系统多址信号的接收进行了解析,对其抗阻塞干扰和跳频干扰的能力进行了分析。基于Matlab,构建了高斯白噪声和多径传输两种无线信道环境,对TDCS系统抗阻塞干扰和跳频干扰的性能进行了仿真分析。仿真结果表明:①在部分频谱可用时,TDCS频谱估计适合采用ARMA谱估计方法,在全部频谱可用时,适合采用AR谱估计方法;②无论是最小公倍数相位映射,还是等间隔相位映射生成的TDCS基函数都具有良好的自相关特性、弱的互相关特性以及伪随机特性,都适用于TDCS多址通信基函数的生成;③只要TDCS频谱数量足够多,系统就具有较强的抗多径衰落、抗阻塞干扰和抗跳频干扰的能力。总而言之,TDCS是一种具有频谱自适应能力的宽带码分多址系统。更多还原

【Abstract】 Being one of the Cognitive Radio (CR) transceiver technologies, the Transform Domain Communication System (TDCS) is an interference-avoiding technology which is suitable for the variety of the electromagnetic environment, because it can actively avoid the jammed frequencies by environmental sampling, spectral estimation, thresholding and notching, and design the communicating signal in transform domain. Basing on the random phase mapping, the pseudorandom (PR) phase vector can respectively give a random phase to every spectrum component in TDCS, and the Basis Function (BF) can make TDCS to communicate with each other in Multiple Access Environment (MAE). TDCS has the characteristic of Low Probability of Intercept (LPI) and the capability of anti-jamming. It gives an available method of solving current spectrum resource scarcity.Firstly, we investigate the spectral estimation methods of TDCS in this paper, which are modeled, simulated and evaluated in Matlab after we propose a model which can simulate the TDCS electromagnetic environment.Secondly, we analyse the characteristic of the PR phase vector and the BF after their basic theories are introduced. Ulteriorly, we discuss the parameter choice, the Multiple Access Capability (MAC) and the symbol demodulation of TDCS, and propose the Least Common Multiple Phase Mapping (LCMPM) and the Equal Interval Phase Mapping (EIPM), which all can generate the BF of TDCS and are simulated in Matlab.Thirdly, we analyse the characteristic of the narrowband block interference, broadband block interference and frequency hopping interference in TDCS after the synchronization detection and symbol demodulation methods are introduced, and we propose two models which can generate the corresponding jamming signal. Ulteriorly, we give the mathematical description of obtaining some or other user signal from the TDCS multiple access signals and analyse the anti-jamming capability of TDCS. In Matlab, we simulate the the anti-jamming performance in Additive White Gaussian Noise (AWGN) and multi-path fading channels.Computer simulation results show that the Autoregressive Moving Average (ARMA) spectral estimation is more suitable for part spectrum available case, whenas the Autoregressive (AR) spectral estimation is more suitable for all spectrum available case, both the LCMPM and the EIPM can generate the BFs in TDCS, and TDCS can effectively combat the narrowband block interference, the broadband block interference and the frequency hopping interference in AWGN and multi-path fading channels as long as it can obtain sufficient spectrum. In a word, TDCS is a spectrum agile and broadband Code Division Multiple Access (CDMA) technology.更多还原