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arXiv 1810.02451cs.ITmath.IT
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一类柔性指标编码问题的紧信息论逆解

Tight Information Theoretic Converse Results for some Pliable Index Coding Problems

Tang Liu, Daniela Tuninetti

摘要:

研究了内容型分销网络的柔性指数编码问题(PICOD)。在PICOD $(t)$问题中,存在$m$消息、$n$用户,并且每个用户具有不同的消息侧信息集,如在经典索引编码问题(IC)中一样。从IC(其中每个用户具有要解码的预先指定的消息集)继承地,在PICOD $(t)$中,用户是“易受影响的”,并且如果其能够解码不在其辅助信息集中的任何$t$消息,则用户是满意的。我们的目标是找到一个长度最短的代码,满足所有用户的需求。在确定所需消息集方面的这种灵活性使得PICOD $(t)$的行为与IC完全不同,并且其分析具有挑战性。本文主要研究具有$m$消息的\emph{complete--$S$} PICOD $(t)$,其中集合$S\subset[m]$包含边信息集的大小,用户数为$n=\sum_{s\in S}\binom{m}{s}$,没有两个用户具有相同的边信息集。示出了以下的容量结果:(i)\emph{consecutive}完全- $S$ PICOD $(t)$,其中$S=[s_{\min}:s_{\max}]$用于一些$0 \leq s_{\min} \leq s_{\max} \leq m-t$,以及(ii)\emph{complement-consecutive}完全- $S$ PICOD $(t)$,其中$S=[0:m-t]\backslash[s_{\min}:s_{\max}]$用于一些$0 < s_{\min} \leq s_{\max} < m-t$。新的逆向证明的灵感来自组合设计技术,关键的洞察力是考虑所有的消息,用户最终可以成功解码,甚至超过$t$所需的。这允许人们规避考虑用户处的所有可能的期望消息集分配以便找到导致最短代码长度的消息集分配的需要。此外,对于具有圆弧网络拓扑超图的PICOD $(1)$,也给出了紧逆结果。

英文摘要:

This paper studies the Pliable Index CODing problem (PICOD), which models content-type distribution networks. In the PICOD$(t)$ problem there are $m$ messages, $n$ users and each user has a distinct message side information set, as in the classical Index Coding problem (IC). Differently from IC, where each user has a pre-specified set of messages to decode, in the PICOD$(t)$ a user is "pliable" and is satisfied if it can decode any $t$ messages that are not in its side information set. The goal is to find a code with the shortest length that satisfies all the users. This flexibility in determining the desired message sets makes the PICOD$(t)$ behave quite differently compared to the IC, and its analysis challenging. This paper mainly focuses on the \emph{complete--$S$} PICOD$(t)$ with $m$ messages, where the set $S\subset[m]$ contains the sizes of the side information sets, and the number of users is $n=\sum_{s\in S}\binom{m}{s}$, with no two users having the same side information set. Capacity results are shown for: (i) the \emph{consecutive} complete--$S$ PICOD$(t)$, where $S=[s_{\min}:s_{\max}]$ for some $0 \leq s_{\min} \leq s_{\max} \leq m-t$, and (ii) the \emph{complement-consecutive} complete--$S$ PICOD$(t)$, where $S=[0:m-t]\backslash[s_{\min}:s_{\max}]$, for some $0 < s_{\min} \leq s_{\max} < m-t$. The novel converse proof is inspired by combinatorial design techniques and the key insight is to consider all messages that a user can eventually decode successfully, even those in excess of the $t$ required ones. This allows one to circumvent the need to consider all possible desired message set assignments at the users in order to find the one that leads to the shortest code length. In addition, tight converse results are also shown for those PICOD$(1)$ with circular-arc network topology hypergraph.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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