LTE中Sounding信号的信噪比估计与定时估计

发布时间：2018-06-27 13:48

本文选题：LTE + 探测参考信号　；参考：《电子科技大学》2014年硕士论文

【摘要】：随着数据通信和多媒体业务的飞速发展,现有的移动通信系统已越来越不能满足人们的需求。因此,3GPP提出了3G的长期演进计划(Long Term Evolution,LTE),意在提供更高的传输速率和更大的系统带宽。作为新一代移动通信的发展方向,LTE受到了全球研究人员和通信业界的广泛关注。LTE系统以OFDM和MIMO作为其物理层关键技术,同时采用了许多新的通信技术,其中一个重要技术就是在系统上行链路定义了两种重要的参考信号:解调参考信号(DeModulation Reference Signal,DMRS)和探测参考信号(Sounding Reference Signal,SRS)。本文主要对SRS进行了研究。本文首先对LTE系统的上行物理层进行了概述,包括无线帧结构、时频资源、子载波映射方式等。简要介绍了LTE的上行多址方式SC-FDMA。接着根据3GPP协议的定义,详细分析了SRS序列的生成方式、序列的循环自相关特性、SRS带宽分配以及时频资源配置等。本文重点研究了基于SRS的信噪比估计算法和定时同步算法。在信噪比估计方面:首先给出了SRS的传输方式和信噪比估计的系统模型;然后简要介绍了三种常用的信噪比估计算法,并针对其各自的缺点,提出了两种改进的算法:改进的DFT算法和改进的DASS算法。改进的DFT算法通过在时域上修正噪声的估计区间,减小了高信噪比时有用信号能量泄露对噪声估计的影响,从而获得更准确的信噪比估计。仿真结果表明,在高信噪比区域,新算法的平均估计性能比Boumard算法和DFT算法提高了约6dB左右;改进的DASS算法通过重新定义子载波的计算方式,减小了噪声估计的误差,使得高信噪比时的性能有了明显提高,并且复杂度仅为原DASS方法的1/3。在定时估计方面:本文首先从理论上对定时误差对系统带来的影响进行了详细分析。然后在现有的两种定时估计算法基础上,提出了一种适用于SRS的改进的后向搜索算法。该方法通过重新定义门限值,根据定时度量函数和新的搜索判决技术来确定多径环境中的第1径的位置,进而得到正确的定时点位置。仿真结果表明该算法能有效地消除判决过程中的旁瓣的影响,系统的正确定时概率有明显提高。最后,本文对多用户条件下的SRS进行了研究,重点研究了码分复用情形下的SRS信噪比估计算法。分别从多用户的信道估计和噪声估计两方面展开了研究,给出了一种消除其他用户干扰的方法,将本文所提的两种改进的信噪比估计算法推广到了多用户环境,并通过计算机仿真验证了算法的有效性。
[Abstract]:With the rapid development of data communication and multimedia services, the existing mobile communication systems have become more and more unable to meet the needs of people. Therefore, 3GPP proposed the long-term evolution plan of 3G (Long Term Evolution, LTE), intended to provide higher transmission rate and larger system band width. As the development direction of the new generation of mobile communications, LTE suffers. The widespread concern of the global researchers and communications industry is the key technology of the.LTE system with OFDM and MIMO, and many new communication technologies are adopted. One of the important technologies is to define two important reference signals in the uplink of the system: the demodulation reference number (DeModulation Reference Signal, DMRS) and the detection. The reference signal (Sounding Reference Signal, SRS). This paper mainly studies SRS. This paper first summarizes the uplink physical layer of LTE system, including wireless frame structure, time frequency resources, subcarrier mapping mode and so on. This paper briefly introduces LTE's uplink multiple access mode SC-FDMA. then according to the definition of 3GPP protocol, analyzes the SRS sequence in detail. Generation mode, cyclic autocorrelation of sequence, SRS bandwidth allocation and time frequency resource allocation. This paper focuses on SRS based SNR estimation algorithm and timing synchronization algorithm. In signal-to-noise ratio estimation, the transmission mode of SRS and the system model of signal to noise ratio estimation are given first, and then three kinds of commonly used letters are briefly introduced. Two improved algorithms, the improved DFT algorithm and the improved DASS algorithm, are proposed for the noise ratio estimation algorithm. The improved DFT algorithm reduces the effect of the signal energy leakage on the noise estimation by modifying the estimation interval of the noise in the time domain, thus obtaining a more accurate estimation of the signal to noise ratio. The real results show that the average estimation performance of the new algorithm is about 6dB around the Boumard algorithm and the DFT algorithm in the high signal to noise ratio region. The improved DASS algorithm reduces the noise estimation error by redefining the calculation method of the subcarrier, and makes the performance of the high signal to noise ratio improved obviously, and the complexity is only 1/ of the original DASS method. 3. in timing estimation, this paper first analyzes the effect of timing error on the system in detail. Then, on the basis of two existing timing estimation algorithms, an improved backward search algorithm for SRS is proposed. By redefining the threshold value, the method is based on the timing measure function and the new search judgment. In order to determine the position of the first path in the multipath environment and get the correct position of the timing point, the simulation results show that the algorithm can effectively eliminate the effect of the sidelobe in the decision process, and the correct timing probability of the system is obviously improved. Finally, this paper studies the SRS under the multi user condition and focuses on the code division multiplexing situation. The SRS signal-to-noise ratio estimation algorithm is studied from two aspects of the multiuser channel estimation and noise estimation, and a method to eliminate other user interference is given. The two improved signal to noise ratio estimation algorithm proposed in this paper is extended to the multi user environment, and the effectiveness of the algorithm is verified by computer simulation.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.5

【参考文献】