OFDM系统中的高维星座旋转技术研究

发布时间：2018-04-15 21:20

本文选题：欧洲第二代地面数字电视广播 + 代数构造　；参考：《西安电子科技大学》2014年硕士论文

【摘要】：本文以OFDM系统中普遍采用的二维星座旋转技术为研究基础,以DVB-T2系统为例首先介绍了数字电视概念、优势和广播方式等概况,研究了国内外地面数字电视广播技术的发展情况,同时列举了各大主流数字电视广播传输标准,继而介绍了本文研究出发点DVB-T2系统的提出背景、系统组织结构和星座旋转技术在该系统中的应用。然后简单研究了国内外现有的实现高维星座旋转技术：代数数论构造旋转矩阵的方法和通过两次旋转实现四维星座旋转的方法。代数数论构造旋转矩阵的方法实现比较复杂,使用时需要根据不同条件找出对应的最小多项式以及满足系统条件的映射函数,而且现在没有对应复杂度比较低的解映射方法,但是构造过程中提到的很多理论对于新方法的设计和分析有很大帮助。该方法从最小化信噪比上界出发的思路也是后续设计高维星座方法的重要出发点,通过该方法可以实现不同维度的星座旋转。原有的通过两次二维星座旋转达到四阶分集增益的方法实现的步骤比较简单,复杂度也比较低,但是设计的信号重组方式不适合复杂信道情况。本文在对上述几种方法进行推导和分析的基础上提出了新的实现四维星座旋转的方法,虽然新方法还是从旋转角度出发基于两次二维星座旋转来实现四阶分集增益,但是抛开了原来的信号重组方法,针对复杂信道环境设计了新的信号组合方式,本文最后针对新四维星座旋转算法的旋转矩阵分析提出了一种改进的最大似然检测算法,使用改进检测算法后系统性能并没有损失同时和原来的四维星座旋转方法相比复杂度也没有增加。同时该设计方法应用在系统里不需要使实虚部经历不同的信道衰落,这样可以避免Q路循环延时技术带来的一些弊端,有助于系统性能的提升。本文第四章以QPSK调制方式为例重点介绍了该方法的步骤和仿真结果。并且对旋转矩阵进行分析比较了不同方法实现最大分集阶数的条件。
[Abstract]:Based on the two-dimensional constellation rotation technology commonly used in OFDM system, this paper firstly introduces the concept, advantages and broadcasting methods of digital television, and studies the development of terrestrial digital television broadcasting technology at home and abroad.At the same time, this paper enumerates the main digital television broadcasting transmission standards, and then introduces the background of the research starting point DVB-T2 system, the system organization structure and the application of constellation rotation technology in this system.Then, the existing techniques to realize the rotation of high-dimensional constellations at home and abroad are briefly studied: the method of constructing rotation matrix by algebraic number theory and the method of realizing rotation of four-dimensional constellations by twice-rotation.The method of constructing rotation matrix based on algebraic number theory is very complicated. It is necessary to find out the corresponding minimum polynomial and the mapping function satisfying the system condition according to different conditions, and there is no solution mapping method with lower corresponding complexity.However, many of the theories mentioned in the construction process are of great help to the design and analysis of new methods.The idea of minimizing the upper bound of signal-to-noise ratio (SNR) is also an important starting point for the subsequent design of high-dimensional constellations, by which the rotation of constellations of different dimensions can be realized.The original method to achieve the fourth order diversity gain by two two dimensional constellation rotation is simple and low complexity, but the signal recombination method is not suitable for complex channel.Based on the derivation and analysis of the above methods, a new method to realize the rotation of four dimensional constellations is proposed in this paper, although the new method is based on the rotation of two two dimensional constellations to realize the fourth order diversity gain.But the original signal recombination method is put aside, and a new signal combination method is designed for complex channel environment. In the end, an improved maximum likelihood detection algorithm is proposed for the rotation matrix analysis of the new four-dimensional constellation rotation algorithm.After using the improved detection algorithm, the system performance is not lost and the complexity is not increased compared with the original four-dimensional constellation rotation method.At the same time, it is not necessary to make the real virtual part go through different channel fading in the system, which can avoid some disadvantages brought by the Q-path cyclic delay technology and help to improve the performance of the system.In chapter 4, the QPSK modulation method is taken as an example to introduce the steps of the method and the simulation results.The conditions of realizing the maximum diversity order by different methods are analyzed and compared.
【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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