基于Turbo同步的联合解调译码技术研究

发布时间：2018-01-10 23:07

本文关键词：基于Turbo同步的联合解调译码技术研究　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】：采用LDPC码、Turbo码的现代通信系统可以工作在距离Shannon限很近的信噪比区域,但是该结论是建立在解调器能够完美地进行载波频率、相位与定时恢复的假设上的。在低信噪比下,传统的解调与译码分离的传输方案不能充分发挥现代信道编码方法的优势,较大的同步误差会导致Turbo/LDPC码具有很差的性能,从而使得整个系统仍然工作在距离Shannon限较远的区域。研究表明,基于Turbo原理的迭代载波相位与符号定时恢复(也称为Turbo同步)技术为此提供了一条有效的解决方案。本文结合中国电子科技集团公司第54研究所的合作课题,利用Shannon极限码的结构特点,提出了一个基于Turbo同步技术的联合解调译码技术方案,极大地改善了低信噪比区域的同步性能。本文的具体工作成果主要包括:1.针对仅有码辅助同步的通信系统,分别给出了对应的迭代符号定时与载波同步算法,然后设计了一个基于Turbo同步的联合解调译码技术方案,将定时恢复和载波同步嵌入到迭代译码过程,并进行仿真实现。2.针对具有独特码辅助的卫星通信系统,分别给出了对应的非迭代符号定时与载波同步算法,然后利用码辅助Turbo同步的思想,提出使用VV(Viterbi A JViterbi A M)算法与加窗搜索算法相结合的方式来恢复频偏,将频偏、初相估计和信道译码构成一个Turbo迭代,并进行了分析仿真。仿真结果表明,所提出的Turbo同步方案与接收端完全已知载波相位和完美定时的系统性能相差在0.5d B之内,且比解调、译码分离形式的解调器性能提高1d B以上,从而极大地改善了低信噪比区的同步性能,使得LDPC、Turbo等Shannon极限码得以在实际系统中获得充分利用。
[Abstract]:The modern communication system using LDPC code can work in the signal-to-noise ratio (SNR) region which is very close to the Shannon limit, but the conclusion is that the demodulator can carry out the carrier frequency perfectly. Under the condition of low SNR, the traditional transmission scheme of demodulation and decoding can not give full play to the advantages of modern channel coding methods. Large synchronization error will lead to poor performance of Turbo/LDPC code, which makes the whole system still work in the region far from the Shannon limit. Iterative Carrier Phase and symbol timing recovery based on Turbo principle (also known as Turbo synchronization). Technology provides an effective solution for this. This paper combined with the China Electronic Science and Technology Corporation of the 54th Institute of cooperation. Based on the structural characteristics of Shannon limit codes, a joint demodulation and decoding scheme based on Turbo synchronization technology is proposed. The performance of synchronization in low signal-to-noise ratio region is greatly improved. The main achievements of this paper include: 1. For only code-assisted synchronization communication system. The corresponding iterative symbol timing and carrier synchronization algorithms are given respectively. Then a joint demodulation and decoding scheme based on Turbo synchronization is designed to embed timing recovery and carrier synchronization into the iterative decoding process. The corresponding non-iterative symbol timing and carrier synchronization algorithms are given for the satellite communication system with unique code-assisted. Then the idea of code-assisted Turbo synchronization is used. In this paper, the method of combining VV(Viterbi A JViterbi A M) algorithm with windowed search algorithm is proposed to recover the frequency offset. The initial phase estimation and channel decoding constitute a Turbo iteration and are analyzed and simulated. The simulation results show that. The performance of the proposed Turbo synchronization scheme is less than 0.5 dB with the receiver fully known carrier phase and perfect timing, and is demodulated. The performance of the demodulator in decode separation form is improved by more than 1dB, which greatly improves the synchronization performance in the low SNR region and makes the LDPC. Shannon limit codes such as Turbo can be fully utilized in practical systems.
【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

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