基于exponentiated Weibull模型的无线光通信LDPC信道编码技术研究

发布时间：2018-03-16 12:36

本文选题：无线光通信　切入点：exponentiated　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】：无线光通信技术是可以实现双向高速传送的一种技术。它具有带宽高、成本低、抗干扰能力突出等优点,受到了研究人员的广泛关注。大气作为无线光通信的传输媒介,充斥着各种物质如气体分子、悬浮微粒等,容易造成光在传输过程中被吸收和散射,进而影响通信质量。针对这一技术问题,研究人员尝试通过信道编码、孔径平均和分集等技术降低大气信道对通信系统性能的影响,取得了较好的效果。低密度奇偶校验码(LDPC)作为线性分组码的典型代表,在高速数据传输以及大容量存储信道中具有逼近Shannon限的误码率性能,被多项国际、国内工业技术标准列为信道编码的主要纠错码。论文基于exponentiated Weibull(EW)大气衰落信道模型,研究了LDPC编码对于FSO光通信系统误码率性能的改善作用,在此基础上,研究了孔径平均、分集等技术的影响。论文主要工作如下:1.基于exponentiated Weibull分布描述接收端光强的概率密度分布,建立了无线光通信LDPC编码的系统模型,推导了OOK和BPSK调制下对数似然比的表达式。进而得到不同湍流、孔径条件、不同的LDPC码字参数和译码算法下误码率随信噪比的变化。研究表明,exponentiated Weibull模型适应于不同强度的湍流,并且与Gamma-Gamma信道模型相比,当孔径平均现象发生时,能更好地描述接收光强。校验矩阵的码率、最大迭代次数和译码算法的选取对系统误码率性能也有一定的影响。2.在上述工作的基础上,构建了无线光通信LDPC-STBC编码系统模型,利用最大似然接收准则推导了LDPC-STBC编码系统的解调算法,进而得到了LDPC译码器的对数似然比。研究了不同大气湍流条件下,LDPC-STBC编码对系统误码特性的影响。仿真结果表明,随着分集数的增加,LDPC-STBC级联编码可以获得更好的编码增益,因此信道编码和分集技术可以很好的改善系统性能。本论文研究成果为无线光通信系统信道编码的设计提供一定的理论参考。
[Abstract]:Wireless optical communication technology is a kind of technology that can realize two-way high-speed transmission. It has the advantages of high bandwidth, low cost, outstanding anti-jamming ability and so on. Filled with various substances such as gas molecules, suspended particles and so on, light is easily absorbed and scattered in the transmission process, thus affecting the quality of communication. In response to this technical problem, researchers try to code through channels. Aperture averaging and diversity techniques reduce the influence of atmospheric channel on the performance of communication system and obtain good results. Low density parity check code (LDPC) is a typical example of linear block codes. In high speed data transmission and large capacity storage channels, the BER performance of approaching the Shannon limit has been listed as the main error-correcting codes in channel coding by many international and domestic industrial technical standards. The effect of LDPC coding on the BER performance of FSO optical communication system is studied. Based on this, the average aperture is studied. The main work of this paper is as follows: 1. Based on the exponentiated Weibull distribution to describe the probability density distribution of light intensity at the receiving end, the system model of LDPC coding for wireless optical communication is established. The expressions of logarithmic likelihood ratio under OOK and BPSK modulation are derived. The variation of BER with signal-to-noise ratio under different turbulence, aperture conditions, different LDPC codeword parameters and decoding algorithm is obtained. It is shown that the modified Weibull model is suitable for turbulence with different intensity. Compared with the Gamma-Gamma channel model, when the average aperture phenomenon occurs, the bitrate of the received light intensity and check matrix can be better described. The maximum number of iterations and the selection of decoding algorithms also affect the BER performance of the system. 2. Based on the above work, a wireless optical communication LDPC-STBC coding system model is constructed. The demodulation algorithm of LDPC-STBC coding system is derived by using the maximum likelihood reception criterion, and the logarithmic likelihood ratio of LDPC decoder is obtained. The effects of LDPC-STBC coding on system error characteristics under different atmospheric turbulence conditions are studied. With the increase of the number of subsets, the concatenated LDPC-STBC code can obtain better coding gain. Therefore, channel coding and diversity techniques can improve the performance of the system. This paper provides a theoretical reference for the design of channel coding in wireless optical communication 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】：TN929.1;TN911.22

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