论文标题
吉尔伯特·瓦尔沙莫夫(Gilbert-Varshamov)附近的显式$ε$平衡的代码的独特解码
Unique Decoding of Explicit $ε$-balanced Codes Near the Gilbert-Varshamov Bound
论文作者
论文摘要
Gilbert-Varshamov Bound(非结构性)建立了距离$ 1/2-ε$的二进制代码和速率$ω(ε^2)$(其中已知$ O(ε^2 \ log(1/ε)$的上限)。 Ta-shma [Stoc 2017]给出了$ε$平衡的二进制代码的明确结构,其中任何两个不同的代码字处于$ 1/2-ε/2 $和$ 1/2+ε/2 $之间的距离,达到了几乎最佳的$ω(ε^{2+β})$,$β\ the $β\ the $ a $ as $ abs $ as $ abs $。 我们开发了(本质上)Ta-Shma构建的代码家族的独特和列表解码算法。我们证明了该家族中的$ε$ - $平衡的代码$ε$平衡的代码:ε^{2+β})$: - 对于所有$ε,β> 0 $都有明确的代码,可以将其唯一的解码为误差,最小距离的一半,$ n^{o_ {ε{ε,β}(1)} $。 - 对于任何独立于$ε$的固定常数$β$,都有明确的代码构造,可以将其独特地解码到时间$(\ log(1/ε))^{o(1)} \ cdot n^{o_β(1)} $的最小距离的一半。 - 对于任何$ε> 0 $,都有明确的$ε$ - 平衡的代码,其费率$ω(ε^{2+β})$,可以被解码为错误$ 1/2-ε'$ in Time $ n^{o__ {o_ {o_ {o_ {o_ {ε,ε,ε',β}(1)(1)} $,$ a $ a $ a $+to $^to 0.0 $。 我们算法的起点是Alev等人的列表解码框架。 [SODA 2020],它使用了Squares SDP层次结构。在那里获得的价格为$ε$。在这里,我们展示了如何克服该框架的最佳速率,该框架获得了唯一的解码算法,以实现接近最佳速率的显式二进制代码。这些代码基于对Ta-Shma构造的简单修改。
The Gilbert-Varshamov bound (non-constructively) establishes the existence of binary codes of distance $1/2 -ε$ and rate $Ω(ε^2)$ (where an upper bound of $O(ε^2\log(1/ε))$ is known). Ta-Shma [STOC 2017] gave an explicit construction of $ε$-balanced binary codes, where any two distinct codewords are at a distance between $1/2 -ε/2$ and $1/2+ε/2$, achieving a near optimal rate of $Ω(ε^{2+β})$, where $β\to 0$ as $ε\to 0$. We develop unique and list decoding algorithms for (essentially) the family of codes constructed by Ta-Shma. We prove the following results for $ε$-balanced codes with block length $N$ and rate $Ω(ε^{2+β})$ in this family: - For all $ε, β> 0$ there are explicit codes which can be uniquely decoded up to an error of half the minimum distance in time $N^{O_{ε, β}(1)}$. - For any fixed constant $β$ independent of $ε$, there is an explicit construction of codes which can be uniquely decoded up to an error of half the minimum distance in time $(\log(1/ε))^{O(1)} \cdot N^{O_β(1)}$. - For any $ε> 0$, there are explicit $ε$-balanced codes with rate $Ω(ε^{2+β})$ which can be list decoded up to error $1/2 - ε'$ in time $N^{O_{ε,ε',β}(1)}$, where $ε', β\to 0$ as $ε\to 0$. The starting point of our algorithms is the list decoding framework from Alev et al. [SODA 2020], which uses the Sum-of-Squares SDP hierarchy. The rates obtained there were quasipolynomial in $ε$. Here, we show how to overcome the far from optimal rates of this framework obtaining unique decoding algorithms for explicit binary codes of near optimal rate. These codes are based on simple modifications of Ta-Shma's construction.