短波通信中64QAM软信息提取及数字跳频数据检测技术

发布时间：2018-06-08 22:19

本文选题：信道估计 + 软信息　；参考：《西安电子科技大学》2014年硕士论文

【摘要】：短波通信在无线通信中一直占有重要地位,但由于多径传播和信道畸变造成的码间干扰会影响系统性能。电子信息技术的发展使短波通信广泛应用,消除码间串扰提高可靠性尤为重要,因此提出了时域均衡技术和块式数据检测技术。首先介绍了短波通信信道的特性,针对短波信道的时变特性,需要一种实时信道估计算法来准确的跟踪信道的变化。文中给出四种实时信道估计方法,对比分析每种算法的适用条件。然后介绍了软判决所需要的软信息,给出64QAM调制信号软信息提取的三种方法,分别为精确对数似然比算法,近似对数似然比算法和简化算法。针对方形64QAM调制星座图,推导了简化方法的计算公式,随后对这三种方法进行了仿真。仿真结果显示,简化算法的性能与其它两种算法的性能相当,但计算复杂度却远远低于另两者。Turbo均衡是一种迭代均衡,利用均衡器与译码器相互传递软信息,来消除码间干扰,提高系统性能。本文根据美军标MIL-STD-188-110C要求,使用256/32的数据块结构、64QAM调制、3 4编码率的LDPC编码,采用基于线性MMSE准则及软干扰抵消准则的时域Turbo均衡技术进行仿真研究。然后,论文研究了消除码间干扰的非迭代块式数据检测技术,分别推导了线性数据检测技术和非线性数据检测技术,这两种技术都是通过交替发送训练序列和未知数据,采用判决反馈的形式来消除码间干扰。结合短波数字跳频通信,论文对非线性块式数据检测算法进行仿真,达到了系统性能要求。
[Abstract]:Shortwave communication plays an important role in wireless communication, but the inter-symbol interference (ISI) caused by multipath propagation and channel distortion will affect the performance of the system. With the development of electronic information technology, shortwave communication is widely used, so it is very important to eliminate inter-symbol crosstalk and improve reliability. Therefore, time-domain equalization and block data detection techniques are proposed. Firstly, the characteristics of HF communication channel are introduced. In view of the time-varying characteristics of HF channel, a real-time channel estimation algorithm is needed to track the channel changes accurately. Four real-time channel estimation methods are presented, and the applicable conditions of each algorithm are compared and analyzed. Then the soft information needed by soft decision is introduced, and three methods for extracting soft information from 64QAM modulation signal are presented, which are exact logarithmic likelihood ratio algorithm, approximate logarithmic likelihood ratio algorithm and simplified algorithm. Based on the quadrate 64QAM modulation constellation, the calculation formula of the simplified method is derived, and then the simulation of the three methods is carried out. Simulation results show that the performance of the simplified algorithm is comparable to that of the other two algorithms, but the computational complexity is much lower than that of the other two. Turbo equalization is an iterative equalization. Improve system performance. According to the requirement of MIL-STD-188-110C, the LDPC code with 256- / 32 data block structure is used to modulate the QAM / 34 coding rate, and the time-domain Turbo equalization technique based on linear MMSE criterion and soft interference cancellation criterion is used to carry out simulation research. Then, this paper studies the non-iterative block data detection technology to eliminate the inter-symbol interference, and deduces the linear data detection technology and the nonlinear data detection technology, both of which are transmitted training sequence and unknown data alternately. Decision feedback is used to eliminate inter-symbol interference (ISI). Combined with HF digital frequency hopping communication, this paper simulates the nonlinear block data detection algorithm and achieves the system performance requirements.
【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】：TN911.22;TN925

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