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Source-optimized irregular repeat accumulate codes with inherent unequal error protection capabilities and their application to scalable image transmission

机译:具有固有的不均等错误保护功能的源优化的不规则重复累积码及其在可伸缩图像传输中的应用

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The common practice for achieving unequal error protection (UEP) in scalable multimedia communication systems is to design rate-compatible punctured channel codes before computing the UEP rate assignments. This paper proposes a new approach to designing powerful irregular repeat accumulate (IRA) codes that are optimized for the multimedia source and to exploiting the inherent irregularity in IRA codes for UEP. Using the end-to-end distortion due to the first error bit in channel decoding as the cost function, which is readily given by the operational distortion-rate function of embedded source codes, we incorporate this cost function into the channel code design process via density evolution and obtain IRA codes that minimize the average cost function instead of the usual probability of error. Because the resulting IRA codes have inherent UEP capabilities due to irregularity, the new IRA code design effectively integrates channel code optimization and UEP rate assignments, resulting in source-optimized channel coding or joint source-channel coding. We simulate our source-optimized IRA codes for transporting SPIHT-coded images over a binary symmetric channel with crossover probability p. When p=0.03 and the channel code length is long (e.g., with one codeword for the whole 512/spl times/512 image), we are able to operate at only 9.38% away from the channel capacity with code length 132380 bits, achieving the best published results in terms of average peak signal-to-noise ratio (PSNR). Compared to conventional IRA code design (that minimizes the probability of error) with the same code rate, the performance gain in average PSNR from using our proposed source-optimized IRA code design is 0.8759 dB when p=0.1 and the code length is 12800 bits. As predicted by Shannon's separation principle, we observe that this performance gain diminishes as the code length increases.
机译:在可伸缩多媒体通信系统中实现不均等错误保护(UEP)的常见做法是在计算UEP速率分配之前设计速率兼容的穿孔信道代码。本文提出了一种新的方法,用于设计针对多媒体源进行了优化的强大的不规则重复累积(IRA)码,并利用UEP的IRA码中的固有不规则性。通过使用信道解码中第一个错误位引起的端到端失真作为代价函数(这很容易由嵌入式源代码的运算失真率函数给出),我们将该代价函数通过密度演化,并获得使平均成本函数(而不是通常的错误概率)最小化的IRA码。由于产生的IRA代码由于不规则而具有固有的UEP功能,因此新的IRA代码设计有效地集成了信道代码优化和UEP速率分配,从而实现了源优化的信道编码或联合源信道编码。我们模拟了源优化的IRA代码,以通过交叉概率p在二进制对称通道上传输SPIHT编码的图像。当p = 0.03且信道代码长度较长时(例如,对于整个512 / spl次/ 512图像使用一个代码字),我们可以在信道容量只有9.38%的情况下以代码长度132380位运行,从而实现就平均峰值信噪比(PSNR)而言,最好的发布结果。与具有相同码率的常规IRA码设计(最大限度地降低错误概率)相比,当p = 0.1且码长为12800位时,使用我们建议的经过源优化的IRA码设计,平均PSNR的性能增益为0.8759 dB 。正如香农的分离原理所预测的那样,我们观察到,随着代码长度的增加,这种性能增益会降低。

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