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arXiv 1102.3526cs.ITcs.SYeess.SYmath.ITmath.OC
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具有任意时间可靠性的线性纠错码

Linear Error Correcting Codes with Anytime Reliability

California Institute of Technology(加州理工学院)

Ravi Teja Sukhavasi, Babak Hassibi

AI总结:

本文研究因果线性码的任意时间可靠性,证明随机线性因果码以高概率满足该性质,并针对二进制擦除信道提出一种平均复杂度恒定的最大似然译码算法。

摘要:

我们考虑码率 R = k/n 的因果线性码,它将 k 维二进制向量序列 {b_t} 映射到 n 维二进制向量序列 {c_t},使得每个 c_t 是 {b_1,b_2,...,b_t} 的函数。对于特定的二进制输入无记忆信道,如果每个时刻,关于 d 个时刻前发送的源比特的出错概率随 d 指数衰减,则称这样的码是任意时间可靠的。任意时间可靠码在交互通信问题中有用,尤其可用于通过噪声信道稳定不稳定的被控对象。Schulman 证明了此类码的存在性,由于其结构,他称之为树码;然而,至今尚未设计出显式构造和易处理的译码算法。在本文中,我们证明任意时间可靠的“线性”码以“高概率”存在,即适当选择的随机线性因果码以高概率是任意时间可靠的。关键在于考虑时不变码(即具有 Toeplitz 生成矩阵和校验矩阵的码),这避免了对所有时间进行联合界。对于二进制擦除信道,我们给出一种简单的最大似然译码算法,其平均复杂度为每时间迭代常数,且给定时间 t 的复杂度超过 KC^3 的概率随 C 指数衰减。我们通过模拟在 BEC 上稳定不稳定被控对象来展示该方法的有效性,并讨论了通信资源利用与控制性能之间的权衡。

英文摘要:

We consider rate R = k/n causal linear codes that map a sequence of k-dimensional binary vectors {b_t} to a sequence of n-dimensional binary vectors {c_t}, such that each c_t is a function of {b_1,b_2,...,b_t}. Such a code is called anytime reliable, for a particular binary-input memoryless channel, if at each time, probability of making an error about a source bit that was sent d time instants ago decays exponentially in d. Anytime reliable codes are useful in interactive communication problems and, in particular, can be used to stabilize unstable plants across noisy channels. Schulman proved the existence of such codes which, due to their structure, he called tree codes; however, to date, no explicit constructions and tractable decoding algorithms have been devised. In this paper, we show the existence of anytime reliable "linear" codes with "high probability", i.e., suitably chosen random linear causal codes are anytime reliable with high probability. The key is to consider time-invariant codes (i.e., ones with Toeplitz generator and parity check matrices) which obviates the need to union bound over all times. For the binary erasure channel we give a simple ML decoding algorithm whose average complexity is constant per time iteration and for which the probability that complexity at a given time t exceeds KC^3 decays exponentially in C. We show the efficacy of the method by simulating the stabilization of an unstable plant across a BEC, and remark on the tradeoffs between the utilization of the communication resources and the control performance.

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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