应哈工大电信学院孟维晓教授、于启月教授邀请，信息论与编码，信息安全领域的国际著名学者、台北大学IEEE Fellow韩永祥教授将于2018年9月1日-2018年9月8日来哈尔滨工业大学访问讲学和交流研讨。并将分别于2018年9月2日、9月7日进行学术讲座，欢迎全校感兴趣的师生参加。

讲学时间：2018年9月2日上午 10:00-11:30

讲学地点：哈工大科学园2A栋1011多媒体教室

讲学题目1:  Efficient Decoding over Unknown Impulsive Noise Channels

报告内容简介：

It has been known from many researches that communication systems are susceptible to memoryless impulsive noise characterized by, for instance, the Bernoulli-Gaussian model. In order to combat this obstacle, channel coding has long served as an effective tool, especially in the context of moderately frequent occurrence of impulses, when the statistics of impulsive noise can be realized at the decoder. In this talk, irrespective of the statistics of impulses, an efficient decoding scheme is introduced by incorporating clipping-featured technique into the Viterbi algorithm. As a result, the proposed decoding scheme, while having a complexity at the same order as that of the Viterbi algorithm, is on a par with its optimal counterpart, for which statistics of impulses is assumed known at receiver, in terms of bit error probability. In addition, the Chernoff bounds of the bit error probabilities of the devised decoding algorithm are derived for both Bernoulli-Gaussian noise model and Middleton Class-A noise model. Comparisons between the bounds we derived and the simulated error rates under a variety of settings indicate that the ensuing analysis can provide critical insights for the efficacy of the proposed decoding approach when dealing with precarious frequent strong impulses.

讲学时间：2018年9月7日上午 10:00-11:30

讲学地点：哈工大科学园2A栋1011多媒体教室

讲学题目1:  Novel FFT over Binary Finite Fields and Its Application to Reed-Solomon Erasure Codes

报告内容简介：

Abstract A fundamental issue in algebra is to reduce the computational complexities of arithmetic operations over polynomials. Many fast polynomialrelated algorithms, such as encoding/decoding of Reed-Solomon codes, are based on fast Fourier transforms (FFT). However, it is algorithmically harder as the traditional fast Fourier transform (FFT) cannot be applied directly over characteristic-2 finite fields. To the best of our knowledge, no existing algorithm for characteristic-2 finite field FFT/polynomial multiplication has provably achieved O(h log2(h)) operations. In this talk, we present a new basis of polynomial over finite fields of characteristic-2 and then apply it to the encoding/decoding of Reed-Solomon erasure codes. The proposed polynomial basis allows that h-point polynomial evaluation can be computed in O(h log2(h)) finite field operations with small leading constant. As compared with the canonical polynomial basis, the proposed basis improves the arithmetic complexity of addition, multiplication, and the determination of polynomial degree from O(h log2(h) log2 log2(h)) to O(h log2(h)). Based on this basis, we then develop the encoding and erasure decoding algorithms for the (n = 2r; k) Reed-Solomon codes. Thanks to the efficiency of transform based on the polynomial basis, the encoding can be completed in O(n log2(k)) finite field operations, and the erasure decoding in O(n log2(n)) finite field operations. To the best of our knowledge, this is the first approach supporting Reed-Solomon erasure codes over characteristic-2 finite fields while achieving a complexity of O(n log2(n)), in both additive and multiplicative complexities. As the complexity of leading factor is small, the algorithms are advantageous in practical applications.

This work was presented at the 55th Annual Symposium on Foundations of Computer Science (FOCS 2014).

报告人简介：

   韩永祥教授1984年毕业于台湾清华大学电机工程学系并于1986年于同系取得硕士学位。1993年韩教授于纽约州雪城大学获得计算机与信息科学博士。他曾于华梵人文科技学院，暨南国际大学，以及台北大学任教。从2010年8月到2017年1月，他任教于台湾科技大学电机工程系并于2011年6月荣任学校讲座教授。2015年2月起，他同时是台北大学讲座教授。目前担任东莞理工学院电子工程与智能化学院杰出人才特聘教授。

   韩教授的研究兴趣主要是在错误控制码，无线网络和资讯安全。韩教授已从事最先进的错误控制码解码研究超过20年。20年前他首先开发了基于A*算法的连续型解码演算法。当时，该演算法吸引了大量的关注，因为它是对二进制线性区块码最有效的最大似然软性决定解码演算法。此解码演算法已被收录于错误控制码的经典教科书中。

   韩教授还成功地应用编码理论于无线传感器网络的研究领域。他已出版几个关于无线传感器网络研究的高被引用着作。其中一篇关于随机密钥预分配方案着作被引用超过二千次。他还担任多个国际学术刊物的编辑。韩教授是1994年雪城大学博士论文奖得主，同时也是IEEE院士。2013年他的一篇论文赢得了久负盛名的ACM CCS Test of Time奖。此奖项为ACM资讯安全领域的年度最有影响力论文奖。