散射信道测量方案的研究

发布时间：2018-05-02 06:48

本文选题：散射信道 + SAGE算法　；参考：《西安电子科技大学》2014年硕士论文

【摘要】：信道在很大程度上决定了通信系统的性能,因此信道测量成为通信系统设计中首要的不可或缺的任务。而散射信道因其变幻莫测性,通常具有路径损耗大、存在时变多径、和因信道中散射体的移动带来的多普勒频移等特点,而导致信道环境比较差,一般的信道测量方法已不能满足对散射信道的测量要求。本文首先分析了散射信道的特点,利用抽头延迟线模型给出了散射信道的有效数学模型。此模型具有较强的概括性和实用性,众多的测量方法和参数提取算法都是基于此数学模型进行的。同时,给出了用来描述信道特征的大尺度和小尺度参数,其中,大尺度参数主要对散射信道的路径损耗特征进行表述,达到对接收信号功率衰减情况的整体把握。小尺度参数包括了时延参数和多普勒参数,分别对信道的时延功率分布情况和多普勒效应进行详细描述。并且考虑到有可能存在较强径的情况,研究了莱斯因子存在的可能性和常用的提取方法。其次,概括性地介绍了信道测量理论和基本要求,调研了已有的信道测量方法,包括时域信道测量方法和频域信道测量方法。其中,重点介绍了备受青睐的滑动相关信道测量方法。根据散射信道的低信噪比且慢变化的特点,提取已有SAGE算法的核心并进行简化,应用到相关测量中来改进滑动相关测量的性能。为了进一步的改进测量可靠性和寻找更高效的测量方法,研究了脉冲压缩体制。通过比较已有脉冲压缩的匹配滤波算法和外差处理算法,采用性能更好的基于chirp信号的脉冲压缩信道测量方法,详细分析了采用这种测量方法所要考虑的各种因素。根据散射信道测量指标,进行了脉冲压缩测量方案的帧结构设计和帧同步设计,并利用chirp信号的连续周期性,创新性地改进了已有的数据处理方法,使得单个周期的测量帧不只是得到一个而是多个信道冲击响应样本,从而对信道的时变特性进行更详细的描述。最后,对已提出的数据处理算法和信道测量方法进行了仿真和实地测量实验。其中,基于SAGE算法的滑动相关信道测量采用仿真分析,对比不同路径数目下的测量性能,发现采用SAGE算法后提取的信道冲击响应的均方误差更小,且在极低信噪比下的相对收益更好。而在实地测量实验中,采用已设计的chirp脉冲压缩方案,对大尺度和小尺度特征进行了提取,较为完整的对被测散射信道进行了描述。经仿真实验和实地测量结果验证了已设计的数据处理算法和信道测量方案的可行性及有效性。
[Abstract]:The channel determines the performance of the communication system to a great extent, so the channel measurement becomes the most important task in the design of the communication system. However, due to its uncertainty, high path loss, time-varying multipath and Doppler frequency shift caused by the movement of scatterers in the channel, the channel environment is poor. General channel measurement methods can not meet the requirements of scattering channel measurement. In this paper, the characteristics of the scattering channel are analyzed, and the effective mathematical model of the scattering channel is given by using the tap delay line model. The model has strong generality and practicability, and many measurement methods and parameter extraction algorithms are based on the mathematical model. At the same time, the large scale and small scale parameters are given to describe the channel characteristics, in which the large scale parameters are mainly used to describe the path loss characteristics of the scattering channel, so as to achieve the overall grasp of the power attenuation of the received signal. Small-scale parameters include delay parameters and Doppler parameters. The power distribution of delay and Doppler effect of the channel are described in detail. Considering the possible existence of strong paths, the possibility of the existence of Rice factor and the common extraction methods are studied. Secondly, the theory and basic requirements of channel measurement are introduced, and the existing channel measurement methods, including time-domain channel measurement and frequency-domain channel measurement, are investigated. Among them, the popular method of sliding correlation channel measurement is introduced. According to the characteristic of low signal-to-noise ratio (SNR) and slow variation of scattering channel, the core of existing SAGE algorithm is extracted and simplified, and applied to the correlation measurement to improve the performance of sliding correlation measurement. In order to improve the reliability of measurement and find a more efficient measurement method, the pulse compression system is studied. By comparing the existing matched filtering algorithm and heterodyne processing algorithm, the better performance of pulse compression channel measurement method based on chirp signal is adopted, and the various factors to be considered in this measurement method are analyzed in detail. According to the measurement index of scattering channel, the frame structure design and frame synchronization design of pulse compression measurement scheme are carried out, and the existing data processing methods are innovatively improved by using the continuous periodicity of chirp signal. The measurement frame of a single period is not only one but a number of channel impulse response samples so that the time-varying characteristics of the channel are described in more detail. Finally, the proposed data processing algorithms and channel measurement methods are simulated and measured in the field. Among them, the sliding correlation channel measurement based on SAGE algorithm is simulated and compared with the measurement performance under different path numbers. It is found that the mean square error of channel impulse response extracted by SAGE algorithm is smaller. And the relative profit is better at very low SNR. In the field measurement experiments, the large scale and small scale characteristics are extracted by using the designed chirp pulse compression scheme, and the scattering channel is described completely. The feasibility and effectiveness of the proposed data processing algorithm and channel measurement scheme are verified by simulation experiments and field measurements.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN926

【相似文献】