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arXiv cs/0408008cs.ITmath.IT
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基于图上编码的迭代Quantization

Iterative Quantization Using Codes On Graphs

Emin Martinian, Jonathan S. Yedidia

摘要:

我们研究代码的图形结合迭代消息传递算法的量化。具体来说,我们考虑的二进制擦除量化(BEQ)问题,这是二元擦除信道(BEC)编码问题的对偶。我们表明,实现BEC产量代码接近最低可能的BEQ率的能力的代码的最大化。相比之下,低密度奇偶检验码不能达到最小速率,除非它们的密度至少随块长度成比例地增长。此外,我们表明,有效的迭代解码算法的BEC产生有效的编码算法的BEQ。因此,我们的研究结果表明,图形模型可能会产生近最佳的代码在信源编码以及在信道编码和对偶起着关键作用,在这样的建设。

英文摘要:

We study codes on graphs combined with an iterative message passing algorithm for quantization. Specifically, we consider the binary erasure quantization (BEQ) problem which is the dual of the binary erasure channel (BEC) coding problem. We show that duals of capacity achieving codes for the BEC yield codes which approach the minimum possible rate for the BEQ. In contrast, low density parity check codes cannot achieve the minimum rate unless their density grows at least logarithmically with block length. Furthermore, we show that duals of efficient iterative decoding algorithms for the BEC yield efficient encoding algorithms for the BEQ. Hence our results suggest that graphical models may yield near optimal codes in source coding as well as in channel coding and that duality plays a key role in such constructions.

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