星基增强系统传输技术研究

发布时间：2018-02-25 16:46

本文关键词： 星基增强系统链路预算 QC-LDPC码信号捕获系统同步　出处：《西安电子科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：作为全球卫星导航系统(Global Navigation Satellite System,GNSS)的组成部分,星基增强系统(Satellite-Based Augmentation System,SBAS)由于其重要的作用而受到国内外学者的广泛关注。SBAS能够为用户提供额外的信息,从而增强定位信号、导航信号和授时信号质量,并能提升导航系统的定位精度、可用性、连续性和完好性。在星基增强系统中,增强信息经地星-星地传输链路传输至用户接收机,该传输链路是否有效、可靠,直接决定了该增强系统的性能。本文对星基增强系统中的地星-星地链路信息传输技术进行了系统的研究,主要工作及所取得的研究成果如下:1.对星基增强系统及其传输链路进行了研究。通过研究已有的星基增强系统及其传输链路结构,给出了系统设计所需考虑的参数;通过链路预算,获得系统链路可用的最低比特信噪比,并提出了一种基于高效编译码的系统传输链路方案。理论分析表明:该方案可满足较高的信息传输速率和较低的系统误码率要求。2.对准循环低密度奇偶校验码(QC-LDPC)进行了研究。介绍了QC-LDPC码的校验矩阵构造方法和编译码方法,重点探讨了基于循环置换矩阵的构造方法和对数域BP译码算法;针对系统高信息传输速率和低误码率的要求,设计了一种1/2码率的(2488,3,6)QC-LDPC码。仿真结果表明:该码在10-7误码率水平可提供约8.8dB的编码增益。3.对星基增强系统的接收端关键技术进行了研究。详细比较了常用的信号捕获算法,针对本系统的信号特点提出了一种基于串行搜索和非相干累加的弱信号捕获方案;研究了锁相环的基本原理,并给出了基于Costas环的载波跟踪方案和基于DLL环的码跟踪方案;采用巴克码滑动相关法实现了系统的位同步和帧同步;基于Matlab仿真平台,搭建了传输链路仿真系统,给出了整体仿真流程图及模块间的衔接关系,并进行了性能仿真分析。
[Abstract]:As an integral part of Global Navigation Satellite system Navigation, the satellite-based Augmentation system SBASs has attracted extensive attention from scholars at home and abroad for its important role. SBAS can provide additional information to users and thus enhance positioning signals. The quality of navigation signals and timing signals, and the improvement of positioning accuracy, availability, continuity and integrity of navigation systems. In space-based augmentation systems, enhancement information is transmitted to the user receiver via the earth-satellite transmission link, Whether the transmission link is effective and reliable directly determines the performance of the enhanced system. The main work and research results are as follows: 1. The space-based enhancement system and its transmission link are studied. By studying the existing space-based enhancement system and its transmission link structure, the parameters that need to be considered in the design of the system are given. Through the link budget, the minimum bit signal-to-noise ratio (SNR) available for the system link is obtained, A system transmission link scheme based on efficient encoding and decoding is proposed. Theoretical analysis shows that the scheme can meet the requirements of higher transmission rate and lower bit error rate (BER) of the system. QC-LDPC is used to align the cyclic low density parity check code. The construction method of check matrix and the method of encoding and decoding of QC-LDPC code are introduced. The construction method based on cyclic permutation matrix and logarithmic domain BP decoding algorithm are discussed, and the requirements of high information transmission rate and low bit error rate of the system are discussed. A 1/2 bit rate QC-LDPC code is designed. The simulation results show that the code can provide a coding gain of about 8.8 dB at the 10-7 bit error rate level. The key technologies of the receiver of the space-based enhancement system are studied, and the commonly used signal acquisition algorithms are compared in detail. According to the signal characteristics of this system, a weak signal acquisition scheme based on serial search and incoherent accumulation is proposed, and the basic principle of phase-locked loop is studied, and the carrier tracking scheme based on Costas loop and the code tracking scheme based on DLL loop are given. Buck code sliding correlation method is used to realize bit synchronization and frame synchronization, and based on Matlab simulation platform, the transmission link simulation system is built, and the overall simulation flow chart and the connection relationship between modules are given, and the performance simulation analysis is carried out.
【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】：TN967.1

【参考文献】