阈值系统中的LDPC译码随机共振研究

发布时间：2018-10-30 12:51

【摘要】：随机共振指的是利用输入信号、噪声和非线性系统间的某种匹配关系,令噪声能量向信号转移,使得噪声降低的同时,信号能量增强,进而使得输出信噪比增强并达到极大值点。利用随机共振可以将噪声视为有利因素,这对非线性系统中信号处理领域的研究具有显著的意义。本文研究了随机共振在信道译码方面的应用,主要工作内容如下:首先,以误比特率(Bit Error Ratio,BER)为测度,研究高斯噪声作用下阈值阵列系统中的随机共振现象及噪声改善LDPC码译码性能的情况。特别研究了阈值单元个数及系统阈值大小的变化对随机共振现象的影响,并发现当信号是阈下时,噪声强度增加,误码率先降后增,随机共振发生,且在阈值单元个数较多时,随机共振现象越明显;当信号是阈上时,噪声总是恶化译码的性能,随机共振不存在。其次,研究了两种图像传输中常见的噪声——瑞利噪声和莱斯噪声作用下,阈值阵列系统中LDPC码的译码性能改善效果。通过对比不同噪声作用的仿真结果,可以发现不同噪声之间的效果差异。特别研究了阈值单元个数及阈值大小的改变对随机共振现象的影响,并发现莱斯噪声作用下阈上随机共振的存在性。最后,研究了图像在LDPC编译码系统中的传输。以峰值信噪比(Peak Signal-to-noise Ratio,PSNR)为衡量标准,展示了噪声对其传输效果的改善作用,以及不同噪声分布对接收端图像质量的影响,证实了噪声对LDPC译码效果改善作用的可应用性。
[Abstract]:Stochastic resonance refers to the use of a certain matching relationship between input signal, noise and nonlinear system to transfer the noise energy to the signal, so as to reduce the noise and increase the signal energy. Then the output signal-to-noise ratio is enhanced and the maximum value is reached. Noise can be regarded as a favorable factor by using stochastic resonance, which is of great significance to the research of signal processing in nonlinear systems. In this paper, the application of stochastic resonance in channel decoding is studied. The main work is as follows: firstly, the bit error rate (Bit Error Ratio,BER) is taken as the measure. The stochastic resonance phenomenon in threshold array system with Gao Si noise and the improvement of decoding performance of LDPC codes by noise are studied. The effects of the number of threshold units and the threshold value of the system on the stochastic resonance are studied. It is found that when the signal is subthreshold, the noise intensity increases, the bit error rate decreases first and then increases, and the stochastic resonance occurs when the number of threshold units is large. The more obvious the phenomenon of stochastic resonance; When the signal is on the threshold, the noise always deteriorates the decoding performance, and the stochastic resonance does not exist. Secondly, the improvement of decoding performance of LDPC codes in threshold array system is studied under the influence of Rayleigh noise and Rice noise, which are common in image transmission. By comparing the simulation results of different noises, we can find the difference between different noises. In particular, the effects of the number of threshold units and the threshold size on the stochastic resonance phenomenon are studied, and the existence of suprathreshold stochastic resonance is found under the influence of Rice noise. Finally, the transmission of image in LDPC codec and decode system is studied. The peak signal-to-noise ratio (Peak Signal-to-noise Ratio,PSNR) is taken as the standard to show the improvement of the transmission effect of noise and the influence of different noise distribution on the image quality of the receiver. It is proved that noise can improve the effect of LDPC decoding.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN911.22

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