SC-FDE系统中信道估计与均衡技术的研究

发布时间：2018-07-22 13:21

【摘要】：单载波频域均衡(SC-FDE)技术,不仅具有较强的对抗频率选择性衰落信道的特性,同时具有较低的峰均比、良好的误码率性能、对载波频偏和相位噪声敏感性小等优势,是宽带无线通信系统中的重要组成技术。在SC-FDE系统中,因为空间无线信道的复杂性,接收端必须采取相应的措施消除信道带来的影响。所以,对信道特性的估计与均衡算法在整个传输系统中起着决定性作用。除此之外,由于系统接收机的模拟前端通常采用正交下变频,这样不可避免的存在同相与正交(IQ)支路幅度和相位的不平衡问题,非常小的IQ不平衡都会影响信道估计的精度。因此,对同相与正交支路之间不平衡因子的估计与补偿算法也很重要。本文围绕单载波频域均衡技术展开研究,重点研究单载波频域均衡的信道估计与均衡算法,主要完成以下研究工作:(1)对传统的信道估计与均衡算法进行详细的理论分析,并对最小均方误差(MMSE)均衡算法中噪声方差估计方案展开研究,引入Boumard在OFDM系统中噪声方差估计方法的思路,将该方法运用到SC-FDE系统中,得到很好的噪声方差估计性能。(2)针对传统的信道估计与均衡算法的缺陷,提出一种基于特殊训练序列的信道估计与均衡改进算法,详细地阐述整个算法的各个实现步骤。由于该算法采取与数据帧等长的Chu序列作为训练序列进行信道估计,从而提高信道估计的精度。并在迫零(ZF)均衡算法基础上,再进行一次反傅里叶变换和傅里叶变换,这些操作都可以借助FFT模块实现,复杂度不是很高,但其性能却在ZF均衡算法基础上有很大提高。(3)针对同相与正交支路之间不平衡因子的估计与补偿算法进行研究,对传统的时域IQ不平衡估计与补偿算法进行详细的分析,由于该算法忽略了IQ不平衡因子与信道估计之间的相互影响,在多径衰落信道环境中,性能较差。因此,本文针对时域方法的不足提出一种频域IQ不平衡与信道联合估计的方案,该方案由于考虑了信道估计与IQ不平衡的相互影响,所以无论是在任何信道下,对IQ不平衡都有一定的补偿作用。(4)通过结合Matlab仿真结果,验证各种方案理论分析的正确性。
[Abstract]:Single carrier frequency domain equalization (SC-FDE) technology not only has strong characteristics of frequency selective fading channel, but also has the advantages of low peak-to-average ratio, good bit error rate performance and low sensitivity to carrier frequency offset and phase noise. Wideband wireless communication system is an important component technology. In SC-FDE systems, due to the complexity of the space wireless channel, the receiver must take appropriate measures to eliminate the influence of the channel. Therefore, the estimation and equalization algorithm of channel characteristics plays a decisive role in the whole transmission system. In addition, because the analog front end of system receiver usually uses quadrature downconversion, it is inevitable that the amplitude and phase of the phase and amplitude of the in phase and quadrature (IQ) branch are unbalanced. The very small IQ imbalance will affect the accuracy of channel estimation. Therefore, it is also important to estimate and compensate the imbalance factor between the same phase and the orthogonal branch. This paper focuses on single-carrier frequency-domain equalization technology, focusing on single-carrier frequency-domain equalization channel estimation and equalization algorithm. The main work is as follows: (1) the traditional channel estimation and equalization algorithm is analyzed in detail. The minimum mean square error (MMSE) equalization scheme is studied. The Boumard method of noise variance estimation in OFDM system is introduced and applied to SC-FDE system. Good performance of noise variance estimation is obtained. (2) aiming at the shortcomings of the traditional channel estimation and equalization algorithm, an improved channel estimation and equalization algorithm based on special training sequence is proposed, and the implementation steps of the whole algorithm are described in detail. The algorithm uses Chu sequence with the same length as the data frame as the training sequence to estimate the channel, thus improving the accuracy of the channel estimation. Based on the zero-forcing (ZF) equalization algorithm, the inverse Fourier transform and Fourier transform are carried out again. These operations can be implemented with FFT module, and the complexity is not very high. However, its performance is greatly improved on the basis of ZF equalization algorithm. (3) the estimation and compensation algorithm of imbalance factor between in-phase and orthogonal branches is studied, and the traditional time-domain IQ imbalance estimation and compensation algorithm is analyzed in detail. Because the algorithm ignores the interaction between IQ imbalance factor and channel estimation, the performance of the algorithm is poor in multipath fading channel. Therefore, this paper proposes a scheme of frequency domain IQ imbalance and joint channel estimation, which takes into account the interaction between channel estimation and IQ imbalance, so it can be used in any channel. It can compensate the IQ imbalance to some extent. (4) by combining the Matlab simulation results, the correctness of the theoretical analysis of various schemes is verified.
【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】：TN929.53

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