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台湾科技大学IEEE Fellow韩永祥教授讲座通知
Editor:刘莹  Updated:2018-08-31  Views:15

应williamhill体育孟维晓教授、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201891-201898日来英国威廉希尔官网访问讲学和交流研讨。并将分别于201892日、97日进行学术讲座,欢迎全校感兴趣的师生加入。


讲学时间:201892日上午 10:00-11:30


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


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:201897日上午 10:00-11:30


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


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).





   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。