Updated on 2022/05/17

写真a

 
NOMURA, Ryo
 
Affiliation
Affiliated organization, Center for Data Science
Job title
Professor

Concurrent Post

  • Affiliated organization   Global Education Center

Education

  •  
     
     

    Waseda University   School of Science and Engineering  

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    Waseda University  

Degree

  • 早稲田大学   博士(工学)

Research Experience

  • 2019.04
    -
    Now

    Waseda University   Center for Data Science   Professor

  • 2018.04
    -
    2019.03

    Senshu University   School of Network and Information   Professor

  • 2012.04
    -
    2018.03

    Senshu University   School of Network and Information   Associate Professor

  • 2010.04
    -
    2012.03

    Senshu University   School of Network and Information   Lecturer

  • 2008.04
    -
    2010.03

    Assistant Professor

  • 2004.10
    -
    2008.03

    Research Assistant, Aoyama Gakuin University

  • 2000.04
    -
    2003.03

    Research Assistant, Waseda University

▼display all

Professional Memberships

  •  
     
     

    IEEE

  •  
     
     

    電子情報通信学会

 

Research Areas

  • Theory of informatics   Theory of informatics

  • Communication and network engineering   Communication/Network engineering

Research Interests

  • >Information Theory

  • >Information Theory, Shannon Theory

Papers

  • Optimum Intrinsic Randomness Rate with Respect to f -Divergences Using the Smooth Min Entropy.

    Ryo Nomura, Hideki Yagi

    IEEE International Symposium on Information Theory(ISIT)     1784 - 1789  2021

    DOI

  • Source Resolvability and Intrinsic Randomness: Two Random Number Generation Problems With Respect to a Subclass of f-Divergences

    Ryo Nomura

    IEEE TRANSACTIONS ON INFORMATION THEORY   66 ( 12 ) 7588 - 7601  2020.12

     View Summary

    This paper deals with two typical random number generation problems in information theory. One is the source resolvability problem (resolvability problem for short) and the other is the intrinsic randomness problem. In the literature, optimum achievable rates in these two problems with respect to the variational distance as well as the Kullback-Leibler (KL) divergence have already been analyzed. On the other hand, in this study we consider these two problems with respect to f-divergences. The f-divergence is a general non-negative measure between two probabilistic distributions on the basis of a convex function f. The class of f-divergences includes several important measures such as the variational distance, the KL divergence, the Hellinger distance and so on. Hence, it is meaningful to consider the random number generation problems with respect to f-divergences. In this paper, we impose some conditions on the function f so as to simplify the analysis, that is, we consider a subclass of f-divergences. Then, we first derive general formulas of the first-order optimum achievable rates with respect to f-divergences. Next, we particularize our general formulas to several specified functions f. As a result, we reveal that it is easy to derive optimum achievable rates for several important measures from our general formulas. The second-order optimum achievable rates and optimistic optimum achievable rates have also been investigated.

    DOI

  • Stochastic Discrete First-Order Algorithm for Feature Subset Selection

    Kota Kudo, Yuichi Takano, Ryo Nomura

    IEICE TRANSACTIONS ON INFORMATION AND SYSTEMS   E103D ( 7 ) 1693 - 1702  2020.07

     View Summary

    This paper addresses the problem of selecting a significant subset of candidate features to use for multiple linear regression. Bertsimas et al. [5] recently proposed the discrete first-order (DFO) algorithm to efficiently find near-optimal solutions to this problem. However, this algorithm is unable to escape from locally optimal solutions. To resolve this, we propose a stochastic discrete first-order (SDFO) algorithm for feature subset selection. In this algorithm, random perturbations are added to a sequence of candidate solutions as a means to escape from locally optimal solutions, which broadens the range of discoverable solutions. Moreover, we derive the optimal step size in the gradient-descent direction to accelerate convergence of the algorithm. We also make effective use of the L-2-regularization term to improve the predictive performance of a resultant subset regression model. The simulation results demonstrate that our algorithm substantially outperforms the original DFO algorithm. Our algorithm was superior in predictive performance to lasso and forward stepwise selection as well.

    DOI

  • Relationship Between Source Resolvability with Normalized f -Divergence and Fixed-Length Coding.

    Ryo Nomura

    IEEE Information Theory Workshop(ITW)     1 - 5  2020

    DOI

  • Optimum Source Resolvability Rate with Respect to f-Divergences Using the Smooth Rényi Entropy.

    Ryo Nomura, Hideki Yagi

    IEEE International Symposium on Information Theory(ISIT)     2286 - 2291  2020

    DOI

  • Overflow Probability of Variable-Length Codes With Codeword Cost

    Ryo Nomura

    IEEE TRANSACTIONS ON INFORMATION THEORY   65 ( 12 ) 8194 - 8206  2019.12

     View Summary

    Lossless variable-length source coding with codeword cost is considered for general sources. The problem setting, where we impose on unequal costs on code symbols, is called the variable-length coding with codeword cost. In this problem, the infimum of average codeword cost have already been determined for general sources. On the other hand, the overflow probability, which is defined as the probability of codeword cost being above a threshold, have not been considered yet. In this paper, we first determine the infimum of achievable threshold in the first-order sense and the second-order sense for general sources with additive memoryless codeword cost. Then, we compute it for some special sources such as i.i.d. sources and mixed sources. A generalization of the codeword cost is also discussed.

    DOI

  • Optimum Overflow Thresholds in Variable-Length Source Coding Allowing Non-Vanishing Error Probability

    Ryo Nomura, Hideki Yagi

    IEEE TRANSACTIONS ON INFORMATION THEORY   65 ( 12 ) 8213 - 8221  2019.12

     View Summary

    The variable-length source coding problem allowing the error probability up to some constant is considered for general sources. In this problem, the optimum mean codeword length of variable-length codes has already been determined. On the other hand, in this paper, we focus on the overflow (or excess codeword length) probability instead of the mean codeword length. The infimum of overflow thresholds under the constraint that both of the error probability and the overflow probability are smaller than or equal to some constant is called the optimum overflow threshold. In this paper, we first derive finite-length upper and lower bounds on these probabilities so as to analyze the optimum overflow thresholds. Then, by using these bounds, we determine the general formula of the optimum overflow thresholds in both of the first-order and second-order forms. Next, we consider another expression of the derived general formula so as to reveal the relationship with the optimum coding rate in the fixed-length source coding problem. Finally, we apply the general formula derived in this paper to the case of stationary memoryless sources.

    DOI

  • Source resolvability problem with respect to a certain subclass of f-divergence

    Ryo Nomura

    2019 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY (ISIT)     2234 - 2238  2019

     View Summary

    This paper deals with the source resolvability problem which is one of typical random number generation problems. In the literatures, the achievable rate in the source resolvability problem with respect to the variational distance as well as the Kullback-Leibler (KL) divergence have been analyzed. On the other hand, in this study we consider the problem with respect to a subclass of f-divergence. The f-divergence is a general non-negative measure between two probabilistic distributions and includes several important measures such as the variational distance, the KL divergence, the Hellinger distance and so on. Hence, it is meaningful to consider the source resolvability problem with respect to the f-divergence. We derive the general formula of the optimum achievable rate for a certain subclass of the f-divergence. Then, we reveal that it is easy to derive previous results from our general formula.

  • Intrinsic Randomness Problem with Respect to a Subclass of f-divergence

    Ryo Nomura

    2019 IEEE INFORMATION THEORY WORKSHOP (ITW)     80 - 84  2019

     View Summary

    This paper deals with the intrinsic randomness (IR) problem, which is one of typical random number generation problems. In the literature, the optimum achievable rates in the IR problem with respect to the variational distance as well as the Kullback-Leibler (KL) divergence have already been analyzed. On the other hand, in this study we consider the IR problem with respect to a subclass of f-divergences. The f-divergence is a general non-negative measure between two probabilistic distributions and includes several important measures such as the total variational distance, the chi(2)-divergence, the KL divergence, and so on. Hence, it is meaningful to consider the IR problem with respect to the f-divergence. In this paper, we assume some conditions on the f-divergence for simplifying the analysis. That is, we focus on a subclass of f-divergences. In this problem setting, we first derive the general formula of the optimum achievable rate. Next, we show that it is easy to derive the optimum achievable rate with respect to the variational distance, the KL divergence, and the Hellinger distance from our general formula.

  • Plane graphs without homeomorphically irreducible spanning trees

    Ryo Nomura, Shoichi Tsuchiya

    ARS COMBINATORIA   141   157 - 165  2018.10

     View Summary

    A homeomorphically irreducible spanning tree (HIST) of a graph G is a spanning tree without vertices of degree 2 in G. Malkevitch conjectured that every 4-connected plane graph has a HIST. In order to solve Malkevitch-conjecture, it is natural to show the existence of a HIST in 3-connected, internally 4-connected (or essentially 4 connected) plane graphs. In this paper, we construct 3-connected, internally 4-connected plane graphs without HISTs. Consequently, such a strategy does not work when we solve Malkevitch-conjecture.

  • First- and Second-Order Hypothesis Testing for Mixed Memoryless Sources

    Te Sun Han, Ryo Nomura

    ENTROPY   20 ( 3 )  2018.03

     View Summary

    The first- and second-order optimum achievable exponents in the simple hypothesis testing problem are investigated. The optimum achievable exponent for type II error probability, under the constraint that the type I error probability is allowed asymptotically up to e, is called the s-optimum exponent. In this paper, we first give the second-order s-optimum exponent in the case where the null hypothesis and alternative hypothesis are a mixed memoryless source and a stationary memoryless source, respectively. We next generalize this setting to the case where the alternative hypothesis is also a mixed memoryless source. Secondly, we address the first-order s-optimum exponent in this setting. In addition, an extension of our results to the more general setting such as hypothesis testing with mixed general source and a relationship with the general compound hypothesis testing problem are also discussed.

    DOI

  • Source Resolvability with Kullback-Leibler Divergence

    Ryo Nomura

    2018 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY (ISIT)     2042 - 2046  2018

     View Summary

    The first- and second-order optimum achievable rates in the source resolvability problem are considered for general sources. In the literature, the achievable rates in the resolvability problem with respect to the variational distance as well as the normalized Kullback-Leibler (KL) divergence have already been analyzed. On the other hand, in this study we consider the source resolvability problem with respect to (unnormalized) KL divergence and derive general formulas of the first- and second-order optimum achievable rates. Relationships with other problems in information theory have also been discussed.

  • Overflow Probability of Codeword Cost in Variable-Length Coding Problem Allowing Non-Vanishing Error Probability

    Ryo Nomura, Hideki Yagi

    PROCEEDINGS OF 2018 INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY AND ITS APPLICATIONS (ISITA2018)     364 - 368  2018

     View Summary

    The variable-length source coding with unequal cost allowing error probability is considered for general sources. In this setting, the first-and second-order optimum mean codeword cost have already been determined. On the other hand, we focus on the overflow probability of codeword cost and determine the general formulas of the first-and second-order optimum achievable overflow threshold. We also apply our general formulas to the stationary memoryless source.

  • Variable-Length Coding with Cost Allowing Non-Vanishing Error Probability

    Hideki Yagi, Ryo Nomura

    IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES   E100A ( 8 ) 1683 - 1692  2017.08

     View Summary

    We consider fixed-to-variable length coding with a regular cost function by allowing the error probability up to any constant epsilon. We first derive finite-length upper and lower bounds on the average codeword cost, which are used to derive general formulas of two kinds of minimum achievable rates. For a fixed-to-variable length code, we call the set of source sequences that can be decoded without error the dominant set of source sequences. For any two regular cost functions, it is revealed that the dominant set of source sequences for a code attaining the minimum achievable rate under a cost function is also the dominant set for a code attaining the minimum achievable rate under the other cost function. We also give general formulas of the second-order minimum achievable rates.

    DOI

  • First- and Second-Order Hypothesis Testing for Mixed Memoryless Sources with General Mixture

    To Sun Han, Ryo Nomura

    2017 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY (ISIT)   20 ( 3 ) 126 - 130  2017

     View Summary

    The first- and second-order optimum achievable exponents in the simple hypothesis testing problem are investigated. The optimum achievable exponent for type II error probability, under the constraint that the type I error probability is allowed asymptotically up to epsilon, is called the epsilon-optimum exponent. In this paper, we first give the second-order epsilon-exponent in the case where the null hypothesis and the alternative hypothesis are a mixed memoryless source and a stationary memoryless source, respectively. We next generalize this setting to the case where the alternative hypothesis is also a mixed memoryless source. We address the first- order epsilon-optimum exponent in this setting.

    DOI

  • Overflow Probability of Variable-Length Codes Allowing Non-Vanishing Error Probability

    Ryo Nomura, Hideki Yagi

    2017 IEEE INFORMATION THEORY WORKSHOP (ITW)     589 - 593  2017

     View Summary

    The variable-length coding problem allowing the error probability up to some constant is considered for general sources. In this problem, we focus on the overflow (or excess codeword length) probability We also consider another expression of our general formula so as to reveal the relationship with the optimum coding rate in the fixed-length source coding problem.

  • First- and Second-Order Coding Theorems for Mixed Memoryless Channels With General Mixture

    Hideki Yagi, Te Sun Han, Ryo Nomura

    IEEE TRANSACTIONS ON INFORMATION THEORY   62 ( 8 ) 4395 - 4412  2016.08

     View Summary

    This paper investigates the first-and second-order maximum achievable rates of codes with/without cost constraints for mixed channels whose channel law is characterized by a general mixture of (at most) uncountably many stationary and memoryless discrete channels. These channels are referred to as mixed memoryless channels with general mixture and include the class of mixed memoryless channels of finitely or countably memoryless channels as a special case. For the mixed memoryless channels with general mixture, the first-order coding theorem which gives a formula for the e-capacity is established, and then a direct part of the second-order coding theorem is provided. A subclass of mixed memoryless channels whose component channels can be ordered according to their capacity is introduced, and the first-and second-order coding theorems are established. It is shown that the established formulas reduce to several known formulas for restricted scenarios.

    DOI

  • Variable-Length Lossy Source Coding Allowing Some Probability of Union of Overflow and Excess Distortion

    Ryo Nomura, Hideki Yagi

    2016 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY     2958 - 2962  2016

     View Summary

    We consider a new concept of achievability in the variable-length lossy source coding on the basis of the probability of the union of the overflow of codeword length and the excess distortion. In this setting, our main concern is to determine the achievable rate-distortion region for a given source and distortion measure. To this end, we first derive non-asymptotic upper and lower bounds, and then we derive general formulas of this achievable rate-distortion region in the first- and second-order sense. Finally, we apply our general formulas to stationary memoryless sources with an additive distortion measure.

    DOI

  • Variable-Length Coding with Cost Allowing Non-Vanishing Error Probability

    Hideki Yagi, Ryo Nomura

    PROCEEDINGS OF 2016 INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY AND ITS APPLICATIONS (ISITA 2016)     16 - 20  2016

     View Summary

    We derive a general formula of the minimum achievable rate for fixed-to-variable length coding with a regular cost function by allowing the error probability up to a constant. E. For a fixed-to-variable length code, we call the set of source sequences that can be decoded without error the dominant set of source sequences. For any two regular cost functions, it is revealed that the dominant set of source sequences for a code attaining the minimum achievable rate with a cost function is also the dominant set for a code attaining the minimum achievable rate with the other cost function. We also give a general formula of the second-order minimum achievable rate.

  • 文字列のもつ帰納的構造の代数的性質に関する考察

    坂本量平

    情報科学研究所 所報   85   >1-7  2015

     View Summary

    共同研究により担当分抽出不可能.指導および構成を担当

  • Variable-Length Coding with Epsilon-Fidelity Criteria for General Sources

    Hideki Yagi, Ryo Nomura

    2015 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY (ISIT)     2181 - 2185  2015

     View Summary

    This paper addresses two problems of variable length coding with a fidelity criterion for general sources, in which either the probability of codeword length overflow or that of excess distortion for a given threshold is allowed up to epsilon. In each problem, a general formula for the achievable region of coding rates and distortion levels is established via information spectrum methods. It is shown that there is a tight connection between the two problems, and the achievable regions are the same under a mild condition on the distortion measure. As a consequence, it turns out that superficially different general formulas for the two coding problems coincide with each other.

    DOI

  • Information Spectrum Approach to Fixed-Length Lossy Source Coding Problem with Some Excess Distortion Probability

    Ryo Nomura, Hideki Yagi

    2015 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY (ISIT)     306 - 310  2015

     View Summary

    This paper deals with a fixed-length lossy source coding problem with some excess distortion probability called the source coding problem with epsilon-fidelity criterion. In this problem, the rate-distortion function and the distortion-rate function have already been characterized for i.i.d. sources with an additive distortion measure in the sense of first-order and second-order coding rates. However, general formulas for these functions have not been revealed up to present. Hence, in this paper we derive general formulas for the rate-distortion function and the distortion-rate function with the epsilon-fidelity criterion in both of the first-order and second-order cases. A relationship between our general formulas and previous results are also discussed.

    DOI

  • First- and Second-Order Coding Theorems for Mixed Memoryless Channels with General Mixture

    Hideki Yagi, Te Sun Han, Ryo Nomura

    2015 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY (ISIT)     2969 - 2973  2015

     View Summary

    This paper studies the first- and second-order maximum achievable rates of codes with/without cost constraints for general mixed channels whose channel law is characterized by a mixture of uncountably many stationary and memoryless discrete channels. These channels are referred to as general mixed memoryless channels and include mixed memoryless channels of finitely or countably many memoryless channels as a special case. For general mixed memoryless channels, the first-order coding theorem which gives a formula for the epsilon-capacity is established, and then a direct part of the second-order coding theorem is provided. A subclass of general mixed memoryless channels whose component channels can be ordered according to their capacity is introduced, and the first- and second-order coding theorems are established. It is shown that the established formulas reduce to several known formulas for restricted scenarios.

  • Second-Order Slepian-Wolf Coding Theorems for Non-Mixed and Mixed Sources

    Ryo Nomura, Te Sun Han

    IEEE TRANSACTIONS ON INFORMATION THEORY   60 ( 9 ) 5553 - 5572  2014.09

     View Summary

    The second-order achievable rate region in Slepian-Wolf source coding systems is investigated. The concept of second-order achievable rates, which enables us to make a finer evaluation of achievable rates, has already been introduced and analyzed for general sources in the single-user source coding problem. Analogously, in this paper, we first define the second-order achievable rate region for the Slepian-Wolf coding system to establish the source coding theorem in the second-order sense. The Slepian-Wolf coding problem for correlated sources is one of typical problems in the multiterminal information theory. In particular, Miyake and Kanaya, and Han have established the first-order source coding theorems for general correlated sources. On the other hand, in general, the second-order achievable rate problem for the Slepian-Wolf coding system with general sources remains still open up to present. In this paper, we present the analysis concerning the second-order achievable rates for general sources, which are based on the information spectrum methods developed by Han and Verdu. Moreover, we establish the explicit second-order achievable rate region for independently and identically distributed (i.i.d.) correlated sources with countably infinite alphabets and mixtures of i.i.d. correlated sources, respectively, using the relevant asymptotic normality.

    DOI

  • Single-Letter Characterization of Epsilon-Capacity for Mixed Memoryless Channels

    Hideki Yagi, Ryo Nomura

    2014 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY (ISIT)     2874 - 2878  2014

     View Summary

    For the class of mixed channels decomposed into stationary memoryless channels, single-letter characterizations of the epsilon-capacity have not been known except for restricted classes of channels such as the regular decomposable channel introduced by Winkelbauer. This paper gives single-letter characterizations of epsilon-capacity for mixed channels decomposed into at most countably many memoryless channels with a finite input alphabet with/without cost constraints. It is shown that the given characterization reduces to the one for the channel capacity given by Ahlswede when epsilon is zero. Some properties of the function of the epsilon-capacity are analyzed.

    DOI

  • Channel Dispersion for Well-Ordered Mixed Channels Decomposed into Memoryless Channels

    Hideki Yagi, Ryo Nomura

    2014 INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY AND ITS APPLICATIONS (ISITA)     35 - 39  2014

     View Summary

    For a class of mixed channels that are decomposed into finitely many stationary memoryless channels, the optimum second-order coding rate, or equivalently, channel dispersion, is derived. The addressed channel, which is an instance of non-ergodic channels, is a sub-class of regular decomposable channels introduced by Winkelbauer. The second-order coding theorem can be viewed as an extension of the coding theorem established by Polyanskiy, Poor, and Verdu for the mixed channel of finitely many binary symmetric channels.

  • Recent Development on Slepian-Wolf Coding Problem

    ノムラ リョウ

      21   >77-85  2013.03

  • Second-Order Resolvability, Intrinsic Randomness, and Fixed-Length Source Coding for Mixed Sources: Information Spectrum Approach

    Ryo Nomura, Te Sun Han

    IEEE TRANSACTIONS ON INFORMATION THEORY   59 ( 1 ) 1 - 16  2013.01

     View Summary

    The second-order achievable asymptotics in typical random number generation problems such as resolvability, intrinsic randomness, and fixed-length source coding are considered. In these problems, several researchers have derived the first-order and the second-order achievability rates for general sources using the information spectrum methods. Although these formulas are general, their computations are quite hard. Hence, an attempt to address explicit computation problems of achievable rates is meaningful. In particular, for i.i.d. sources, the second-order achievable rates have earlier been determined simply by using the asymptotic normality. In this paper, we consider mixed sources of two i.i.d. sources. The mixed source is a typical case of non-ergodic sources and whose self-information does not have the asymptotic normality. Nonetheless, we can explicitly compute the second-order achievable rates for these sources on the basis of two-peak asymptotic normality. In addition, extensions of our results to more general mixed sources, such as a mixture of countably infinite i.i.d. sources or Markov sources, and a continuous mixture of i.i.d. sources, are considered.

    DOI

  • Second-Order Slepian-Wolf Coding Theorems for Non-Mixed and Mixed Sources

    Ryo Nomura, Te Sun Han

    2013 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY PROCEEDINGS (ISIT)     1974 - +  2013

     View Summary

    The second-order achievable rate region in Slepian-Wolf source coding systems is investigated. The concept of second-order achievable rates, which enables us to make a finer evaluation of achievable rates, has already been introduced and analyzed for general sources in the single-user source coding problem. Accordingly, in this paper, we first define the second-order achievable rate region for the Slepian-Wolf coding system and establish the source coding theorem for general sources in the second-order sense. Moreover, we compute the explicit second-order achievable rate region for i.i.d. correlated sources with countably infinite alphabets and mixed correlated sources, respectively, using the relevant asymptotic normality.

  • Information Spectrum Approach to Overflow Probability of Variable-Length Codes with Conditional Cost Function

    Ryo Nomura, Toshiyasu Matsushima

    2012 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY PROCEEDINGS (ISIT)     >1102-1106  2012

     View Summary

    Lossless variable-length source coding with unequal cost function is considered for general sources. In this problem, the codeword cost instead of codeword length is important. The infimum of average codeword cost has already been determined for general sources. We consider the overflow probability of codeword cost and determine the infimum of achievable overflow threshold. Our analysis is on the basis of information-spectrum methods and hence valid through the general source.

  • Second-Order Achievable Rates in Random Number Generation for Mixed Sources

    Ryo Nomura, Te Sun Han

    2012 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY PROCEEDINGS (ISIT)     816 - 820  2012

     View Summary

    The second-order achievable rates in typical random number generation problems are considered. In these problems, several researchers have derived the first-order and the second-order achievability rates for general sources using the information spectrum methods. Although these formulas are general, their computation are quite hard. Hence, an attempt to address explicit computation problems of achievable rates is meaningful. In this paper, we consider mixed sources of two i.i.d. sources and compute the second-order achievable rates explicitly.

  • An Analysis of Slepian-Wolf Coding Problem Based on the Asymptotic Normality

    Ryo Nomura, Toshiyasu Matsushima

    IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES   E94A ( 11 ) 2220 - 2225  2011.11

     View Summary

    Source coding theorem reveals the minimum achievable code length under the condition that the error probability is smaller than or equal to some small constant. In the single user communication system, the source coding theorem was proved for general sources. The class of general source is quite large and it is important result since the result can be applied for a wide class of sources. On the other hand there are several studies to evaluate the achievable code length more precisely for the restricted class of sources by using the restriction. In the multi-user communication system, although the source coding theorem was proved for general correlated sources, there is no study to evaluate the achievable code length more precisely. In this study, we consider the stationary memoryless correlated sources and show the coding theorem for Slepian-Wolf type problem more precisely than the previous result.

    DOI

  • On the Overflow Probability of Fixed-to-Variable Length Codes with Side Information

    Ryo Nomura, Toshiyasu Matsushima

    IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES   E94A ( 11 ) 2083 - 2091  2011.11

     View Summary

    The overflow probability is one of criteria that evaluate the performance of fixed-to-variable length (FV) codes. In the single source coding problem, there were many researches on the overflow probability. Recently, the source coding problem for correlated sources, such as Slepian-Wolf coding problem or source coding problem with side information, is one of main topics in information theory. In this paper, we consider the source coding problem with side information. In particular, we consider the FV code in the case that the encoder and the decoder can see side information. In this case, several codes were proposed and their mean code lengths were analyzed. However, there was no research about the overflow probability. We shall show two lemmas about the overflow probability. Then we obtain the condition that there exists a FV code under the condition that the overflow probability is smaller than or equal to some constant.

    DOI

  • KL情報量を制約としたResolvability問題における達成可能条件の評価

    電子情報通信学会論文誌   J93-A ( 3 ) >216-221  2010.03

  • 多端子情報理論にもとづくセンサネットワークのモデル化と信頼度評価

    野村 亮

    情報処理学会論文誌:数理モデル化と応用   3 ( 1 ) >13-24  2010.01

  • On the Overflow Probability of Fixed-to-Variable Length Codes with Side Information

    Ryo Nomura, Toshiyasu Matsushima

    2010 DATA COMPRESSION CONFERENCE (DCC 2010)     548 - 548  2010

     View Summary

    We consider the source coding problem with side information. Especially, we consider the FV code in the case that the encoder and the decoder can see side information. We obtain the condition that there exists a FV code under the condition that the overflow probability is smaller than or equal to some constant.

    DOI

  • On the Overflow Probability of Lossless Codes with Side Information

    Ryo Nomura, Toshiyasu Matsushima

    2010 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY     131 - 135  2010

     View Summary

    Lossless fixed-to-variable(FV) length codes are considered. The overflow probability is one of criteria that evaluate the performance of FV code. In the single source coding problem, there were many researches on the overflow probability. Recently, the source coding problem for correlated sources, such as Slepian-Wolf coding problem or source coding problem with side information, is one of main topics in information theory. In this paper, we consider the source coding problem with side information. Especially, we consider the FV code in the case that the encoder and the decoder can see side information. In this case, several codes were proposed and their mean code lengths were analyzed. However, there was no research about the overflow probability. We shall show two lemmas about the overflow probability. Then we obtain the condition that there exists a FV code under the condition that the overflow probability is smaller than or equal to some constant.

    DOI

  • On the Condition of epsilon-Transmissible Joint Source-Channel Coding for General Sources and General Channels

    Ryo Nomura, Toshiyasu Matsushima, Shigeichi Hirasawa

    IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES   E92A ( 11 ) 2936 - 2940  2009.11

     View Summary

    The joint source-channel coding problem is considered. The joint source-channel coding theorem reveals the existence of a code for the pair of the source and the channel under the condition that the error probability is smaller than or equal to epsilon asymptotically. The separation theorem guarantees that we can achieve the optimal coding performance by using the two-stage coding. In the case that epsilon = 0, Han showed the joint source-channel coding theorem and the separation theorem for general sources and channels. Furthermore the epsilon-coding theorem (0 <= epsilon < 1) in the similar setting was studied. However, the separation theorem was not revealed since it is difficult in general. So we consider the separation theorem in this setting.

    DOI

  • The Minimum Error Decoding Function and the Channel Capacity in Universal Channel Coding

    野村 亮

    International Journal of Mathematical Sciences and Engineering Applications   3 ( 3 ) >21-33  2009.09

  • On Precise Achievable Conditions in Resolvability Problem Based on the Asymptotic Normality

    野村 亮

    Far East Journal of Electronics and Communications   3 ( 2 ) >85-99  2009.08

  • On the Condition of epsilon-Transmissibility in Joint Source-Channel Coding for Mixed Sources and Mixed Channels

    Ryo Nomura, Toshiyasu Matsushima, Shigeichi Hirasawa

    2008 INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY AND ITS APPLICATIONS, VOLS 1-3     1299 - +  2008

     View Summary

    In this study, we consider a joint source-channel coding problem. The joint source-channel coding theorem reveals the existence of a code for the pair of the source V and the channel W under the condition that the probability of error is smaller than or equal to E asymptotically. We show the separation theorem for general sources and general channels.

  • A note on the epsilon-overflow probability of lossless codes

    Ryo Nomura, Toshiyasu Matsushima, Shigeichi Hirasawa

    IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES   E90A ( 12 ) 2965 - 2970  2007.12

     View Summary

    In this letter, we generalize the achievability of variable-length coding from two viewpoints. One is the definition of an overflow probability, and the other is the definition of an achievability. We define the overflow probability as the probability of codeword length, not per symbol, is larger than eta(n) and we introduce the epsilon-achievability of variable-length codes that implies an existence of a code for the source under the condition that the overflow probability is smaller than or equal to epsilon. Then we show that the epsilon-achievability of variable-length codes is essentially equivalent to the epsilon-achievability of fixed-length codes for general sources. Moreover by using above results, we show the condition of epsilon-achievability for some restricted sources given epsilon.

    DOI

  • 無歪み情報源符号化におけるオーバーフロー確率について

    電子情報通信学会論文誌   J90-A ( 4 ) >292-304  2007.04

     View Summary

    担当:1-6章(14/14頁)/現在の圧縮アルゴリズム(符号)の性能評価には主に平均符号長に基づいて行われてきた。JPEG2000にも採用されている算術符号も、平均符号長の点から考えて高性能な符号である。平均符号長とはその符号を用いて符号化した際の符号化後の平均的な長さを表しており、その符号の平均的な性能を表している。一方、センサーネットワーク等への応用を考えた際にはアルゴリズムの平均的な性能の評価のみでは不十分であると言われており、様々な評価基準が提案されている。オーバーフロー確率もその一つであり、平均的な性能ではなく、その符号にとって悪条件の場合の性能を表している。本研究では、各種符号のオーバーフロー確率を理論的に評価した。対象とした符号の中には、平均符号長の意味で最適な符号も含まれており、現在実用化されている符号のオーバーフロー確率を評価したと考えられる。この結果は実用化対象の符号を理論的な側面から評価した

  • On the epsilon-overflow probability of lossless codes

    Ryo Nomura, Toshiyasu Matsushima, Shigeichi Hirasawa

    2007 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY PROCEEDINGS, VOLS 1-7   E90-A ( 12 ) 441 - +  2007

     View Summary

    In this paper, we generalize the achievability of variable-length coding from two viewpoints. One is the definition of an overflow probability, and the other is the definition of an achievability. We define the overflow probability as the probability of codeword length, not per symbol, is larger than eta(n) and we introduce the epsilon-achievability of variable-length codes that implies an existence of a code for the source under the condition that the overflow probability is smaller than or equal to epsilon.Then we show that the epsilon-achievabitity of variable-length codes is essentially equivalent to the epsilon-achievability of fixed-length codes for general sources. Moreover we show the condition of epsilon-achievability for some restricted sources given epsilon.

    DOI

  • メモリ量を低減した近似ベイズ符号化アルゴリズム

    電子情報通信学会論文誌   J86-A ( 1 ) >46-59  2003.01

     View Summary

    担当:1-5章(14/14頁)/現在、zipやlzhとして実用化されている圧縮ソフトウェアは1970年代後半に提案されたLZアルゴリズムが元となっている。一方1990年代後半に理論上はその性能を上回るアルゴリズムが提案されており、実用化が待たれている。しかし、そのベイズ符号化アルゴリズムは(時間)計算量にいては効率的であるものの必要とするメモリ容量(空間計算量)がデータ長に対して指数的に増えるという欠点を持っていた。本論文では、ベイズ符号化アルゴリズムの実用化に向けてメモリ容量を低減した近似アルゴリズムを提案した。さらに提案したアルゴリズムの圧縮性能について理論と実験の双方から評価した。従来、この分野では実用化に向けてメモリ容量の問題点を改善したアルゴリズムの提案はされていたが、提案のみで理論的な評価が行われている研究はほとんどんない。すなわち、本研究は理論的な性能評価と実用化への課題を双方行っているという意味で非常に意味

  • ウェーブレットパケット基底を用いた信号推定におけるベイズ決定理論の適用に関する一考察

    電子情報通信学会論文誌   J85-A ( 5 ) >584-596  2002.05

▼display all

Books and Other Publications

  • 漸近正規性を用いた可変長無歪み情報源符号化の性能評価に関する研究

    野村 亮( Part: Sole author)

    早稲田大学  2007.12

     View Summary

    学位論文

Misc

  • Fixed-Length Lossy Source Coding Theorems with Small Excess Distortion Probability

    NOMURA Ryo, YAGI Hideki

    IEICE technical report. Information theory   114 ( 138 ) 71 - 76  2014.07

     View Summary

    This paper deals with a fixed-length lossy source coding problem with a fixed excess distortion probability called the source coding problem with ε-fidelity criterion. Several researchers have determined the rate-distortion function and the distortion-rate function with the ε-fidelity criterion for discrete memoryless sources in the first-order and the second-order sense. However, there have been no studies about general formulas for this problem. In this paper, we derive the rate-distortion function and the distortion-rate function with the ε-fidelity criterion for general sources in the first-order sense and the second-order sense. Then, we consider the relationship between our general formulas and previous results.

    CiNii

  • Coding with a Fidelity Criterion Allowing Some Overflow Probability

    YAGI Hideki, NOMURA Ryo

    IEICE technical report. Information theory   114 ( 138 ) 77 - 82  2014.07

     View Summary

    This paper addresses a problem of variable length coding for which the probability of codeword length overflow is admitted up to e with a fidelity criterion for general sources. A general formula for the achievable region of coding rates and distortion levels is established for general sources via information spectrum methods. It is shown that there is a tight connection between variable-length coding admitting the overflow probability up to e and fixed-length coding admitting the excess distortion probability up to s with a fidelity criterion. As a consequence, it turns out that superficially different general formulas for the two coding problems coincide with each other.

    CiNii

  • Overflow Probability of Variable Length Codes with Cost Function for Mixed Sources

    NOMURA Ryo

    IEICE technical report. Information theory   112 ( 382 ) 59 - 64  2013.01

     View Summary

    ossless variable-length source coding with cost function is considered for mixed i.i.d. sources. The problem setting, where we impose on unequal costs on code symbols, is called the variable-length coding with codeword cost or the variable-length coding with cost function. In this problem, the infimum of average codeword cost have been determined for general sources. The overflow probability, which is defined as the probability of codeword cost being above a threshold, has also been considered for general sources. In particular, the general formula for the infimum of achievable threshold has been determined. However, the computation of its general formula is quite hard in general. So in this paper, we try to specify this quantity for mixed i.i.d. sources.

    CiNii

  • 「無歪み情報源符号化におけるオーバーフロー確率について」

    電子情報通信学会論文誌(電子情報通信学会)   J90-A ( 4 ) 292 - 304  2007

  • On the epsilon-overflow probability of lossless codes

    Ryo Nomura, Toshiyasu Matsushima, Shigeichi Hirasawa

    2007 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY PROCEEDINGS, VOLS 1-7   E90-A ( 12 ) 441 - +  2007

     View Summary

    In this paper, we generalize the achievability of variable-length coding from two viewpoints. One is the definition of an overflow probability, and the other is the definition of an achievability. We define the overflow probability as the probability of codeword length, not per symbol, is larger than eta(n) and we introduce the epsilon-achievability of variable-length codes that implies an existence of a code for the source under the condition that the overflow probability is smaller than or equal to epsilon.
    Then we show that the epsilon-achievabitity of variable-length codes is essentially equivalent to the epsilon-achievability of fixed-length codes for general sources. Moreover we show the condition of epsilon-achievability for some restricted sources given epsilon.

    DOI

Research Projects

  • Information Spectrum Approach to Source Coding Problems with Unknown Parameters

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

    Project Year :

    2018.04
    -
    2022.03
     

  • Explicit Analysis of Multi-Terminal Information Theory with Unknown Parameters

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

    Project Year :

    2014.04
    -
    2018.03
     

    Nomura Ryo

     View Summary

    We have analyzed fundamental properties of information theory. In particular, we have considered mixed sources and mixed channels, and derived the fundamental limits on the reliable communication. The situation where we know the class of probabilistic model but we do not know its parameter, can be formulated by the mixed probabilistic models. Hence, our approach is meaningful from the view point of the practical situation.
    We have determined the optimal first- and second-order achievable rates or rate regions in several problems.

  • A Unified Analysis and Optimization of Information Security System with Probabilistic Components from Viewpoints of Convenience and Safety

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

    Project Year :

    2013.04
    -
    2016.03
     

    MATSUSHIMA Toshiyasu, UKITA Yoshifumi, YOSHIDA Takahiro, NOMURA Ryo, SUKO Tota, HORII Shunsuke

     View Summary

    Information security problem with probabilistic components has been formulated by probabilistic models. Theoretical criteria for evaluation such as convenience and safety have been defined clearly and optimal attack or an authentication method has been derived theoretically. Theoretical safety bounds have been evaluated with respect to mathematical models with unified framework for each cipher or security system. A theoretical safety bound or optimality has been clarified with respect to a tradeoff between convenience and safety. New theoretical criteria have been derived for information security systems. Approximation algorithms with high performance for optimal attack or an authentication method have been constructed applying results of studies on problems in related fields such as learning or optimization theory that is formulated by probabilistic models equivalent to our study. Convenience or safety of information security systems has been simulated by applying these algorithms.

  • Reliable communication on the sensor network with unknown probabilistic structure

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)

    Project Year :

    2011
    -
    2013
     

    NOMURA Ryo

     View Summary

    We have analyzed fundamental properties of sensor network on the basis of the multi-terminal information theory. In particular, we have considered the mixed sources and mixed channels, and derived the fundamental limits on the reliable communication. This is because some situations in which we know the class of probabilistic model but we do not know its parameter, can be formulated by the mixed models. We have determined the optimal second-order achievable rates in the single source coding problem and the optimal achievable rate region in the multi-terminal source coding problem. Moreover, we have observed that the optimal achievable rates in some problems on channel coding can be determined by using the similar approach.

  • A Study on Unified Attack against Stream Ciphers based on Probabilistic Inference Algorithms

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

    Project Year :

    2010
    -
    2012
     

    MATSUSHIMA Toshiyasu, UKITA Yoshihumi, NOMURA Ryo

     View Summary

    Attack against Stream Cipher reduces to attack against a pseudo random generator. In this study, attack against a pseudo-random number generator was classified based on the choice of target variables and its order and the choice of the local relationships used for attack. We proposed efficient and accurate attack algorithms based on probabilistic inference by studying the problem in unified framework. We revealed the class of pseudo-random number generators that we can attack against based on the acquired knowledge of probabilistic inference so far.

  • An Evaluation of the Reliability in Sensor Network with Partially Unknown Structure on the basis of the Multi-terminal Information Theory

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)

    Project Year :

    2009
    -
    2010
     

    NOMURA Ryo

     View Summary

    In this research, we have analyzed fundamental properties of sensor network on the basis of multi-terminal information theory. In almost all previous researches in multi-terminal information theory, the probabilities of sensing objects and/or noise in communication were assumed to be known. However, in practical setting, these probabilities maybe unknown and hence we have considered the situation that these probabilities are unknown. In this situation, we have clarified the condition that there exists a code, whose error probability is required to be smaller than or equal to some constant.

  • 情報伝送における信頼度の限界と高信頼度達成アルゴリズムに関する研究

    日本学術振興会  科学研究費助成事業 若手研究(B)

    Project Year :

    2003
     
     
     

    野村 亮

  • Performance Evaluation of Source Code Based on Asymptotic Normality

  • Universal Source Coding

▼display all

Presentations

  • f-ダイバージェンスの部分クラスと情報源Resolvability

    情報理論研究会  (やまと会議室(奈良県))  電子情報通信学会

    Presentation date: 2018.07

  • Source resolvability with Kullback-Leibler divergence

    2018 IEEE International Symposium on Information Theory  (Vail, Colorado, USA)  IEEE Information Theory Society

    Presentation date: 2018.06

  • Overflow Probability of Variable-Length Codes Allowing Non-Vanishing Error Probability

    IEEE Information Theory Workshop 2017  (Kaohsiung, Taiwan)  IEEE

    Presentation date: 2017.11

  • First- and Second-Order Optimistic Coding Theorems on Variable-Length Codes Allowing Non-Vanishing Error Probability

    IEICE Technical Committee Conference on Information Theory  IEICE

    Presentation date: 2017.09

  • First- and second-order hypothesis testing for mixed memoryless sources with general mixture

    2017 IEEE International Symposium on Information Theory  IEEE

    Presentation date: 2017.06

  • Overflow Probability of Variable-Length Codes Allowing Non-Vanishing Error Probability

    IEICE Technical meeting of Information Theory  IEICE

    Presentation date: 2017.03

  • Variable-Length Coding with Cost Allowing Non-Vanishing Error Probability

    2016 International Symposium on Information Theory and Its Applications  (Monterey, California)  IEICE

    Presentation date: 2016.10

  • Variable-Length Coding with Cost Allowing Non-Vanishing Error Probability

    Presentation date: 2015.11

  • First- and Second-Order Coding Theorems for Mixed Memoryless Channels with General Mixture

    2015 IEEE International Symposium on Information Theory  (Hong Kong)  IEEE

    Presentation date: 2015.07

  • Optimistic Coding with an Epsilon-Fidelity Criterion and Strong Converse Theorem

    SITA2014  IEICE

    Presentation date: 2014.12

  • Source Coding Theorem with a Fidelity Criterion Allowing Some Probability of Union of Overflow and Excess Distortion

    SITA2014  IEICE

    Presentation date: 2014.12

  • Channel Dispersion for Well-Ordered Mixed Channels Decomposed Into Memoryless Channels

    International Symposium on Information Theory and Its Applications  IEICE

    Presentation date: 2014.10

  • Coding with a Fidelity Criterion Allowing Some Overflow Probability

    Technical Meeting of Information Theory  IEICE

    Presentation date: 2014.07

  • Fixed-Length Lossy Source Coding Theorems with Small Excess Distortion Probability

    IEICE

    Presentation date: 2014.07

  • Single-Letter Characterization of Epsilon-Capacity for Mixed Memoryless Channels

    Technical Meeting on Information Theory  IEICE

    Presentation date: 2014.03

  • Channel Dispersion for a Class of Mixed Channels Decomposed into Stationary Memoryless Channels

    36th Symposium on Information Theory and its Applications 

    Presentation date: 2013.11

  • Evaluation of the Minimum Overflow Threshold for Bayes Codes

    36th Symposium on Information Theory and its Applications  SITA

    Presentation date: 2013.11

  • Relationship between the Overflow Probability of Variable-length Coding and the Error Probability of Fixed-length Coding

    36th Symposium on Information Theory and its Applications  Sub-Society of Information Theory and its Applications

    Presentation date: 2013.11

  • Second-order achievable rates in resolvability problem with respect to KL-Divergence

    Presentation date: 2013.10

  • Second-Order Slepian-Wolf Coding Theorems for Non-Mixed and Mixed Sources

    IEEE International Symposium on Information Theory  IEEE

    Presentation date: 2013.07

  • Overflow Probability of Variable Length Codes with Cost Function for Mixed Sources

    Presentation date: 2013.01

  • Second-Order Slepian-Wolf Source Coding Theorems

    The 35th Symposium on Information Theory and Its Applications 

    Presentation date: 2012.12

  • Second-Order Achievable Rates in Random Number Generation for Mixed Sources

    2012 IEEE International Symposium on Information Theory  IEEE

    Presentation date: 2012.07

  • Overflow Probability of Variable-length Codes with Unequal Costs on Code symbols

    Presentation date: 2011.11

  • Second-Order Source Coding Theorem for Slepian-Wolf Coding Problem

    電子情報通信学会情報理論研究会  電子情報通信学会

    Presentation date: 2011.09

  • Achievable Condition in Resolvability Problem for Mixed Sources

    33rd ymposium on Information Theory and its Applications 

    Presentation date: 2010.12

  • On the Overflow Probability of Lossless Codes with Side Information

    2010 IEEE International Symposium on Information Theory  (Austin, Texas)  IEEE

    Presentation date: 2010.06

  • On the Overflow Probability of Fixed-to-Variable Length Codes with Side Information

    Presentation date: 2010.03

  • A Note on the Second Order Separate Source Coding Theorem for Sources with Side Information

    Presentation date: 2009.12

  • WDMパッシブローカル網の光パス接続制御方式の研究

    電子情報通信学会フォトニックネットワーク研究会  電子情報通信学会

    Presentation date: 2009.11

  • 相関のある情報源における符号化定理に関する一考察

    第7回シャノン理論ワークショップ  情報理論とその応用学会

    Presentation date: 2009.09

  • A Note on Fixed-Length Coding Theorem for Sources with Side Information

    電子情報通信学会情報理論研究会  電子情報通信学会

    Presentation date: 2009.09

  • 光ハブを用いた光ローカルネットワークの構成

    電子情報通信学会第5回ネットワークソフトウェア研究会  電子情報通信学会

    Presentation date: 2008.12

  • On the Joint Source-Channel Coding for Mixed Sources and Mixed Channels

    2008 International Symposium on Information Theory and Its Applications 

    Presentation date: 2008.12

  • An Information Spectrum Consideration on the Universal Joint Source-Channel Coding

    Pre-ICM International Convention on Mathematical Sciences  Pre-ICM International Convention on Mathematical Sciences

    Presentation date: 2008.12

  • On the Overflow Probability of Lossless Codes for Mixed Sources

    Presentation date: 2008.10

  • A Note on the Weak Universal Joint Source-Channel Coding

    Presentation date: 2008.01

  • 混合情報源におけるε達成可能なオーバーフローしきい値に関する考察

    第30回情報理論とその応用学会  情報理論とその応用学会

    Presentation date: 2007.11

  • On the epsilon-overflow probability of Lossless codes

    2007 IEEE International Symposium on Information Theory 

    Presentation date: 2007.06

  • On the Condition of Epsilon-Achievable Overflow Thresholds for Parametric Compound Source

    電子情報通信学会情報理論研究会  電子情報通信学会

    Presentation date: 2007.05

  • A note on the epsilon-overflow probability of lossless codes

    第29回情報理論とその応用学会  情報理論とその応用学会

    Presentation date: 2006.11

  • 光導波路を用いたAE検出システムの検討

    第16回マイクロエレクトロニクスシンポジウム  エレクトロニクス実装学会

    Presentation date: 2006.10

  • ユニバーサル通信路符号化における通信路容量について

    電子情報通信学会情報理論研究会  電子情報通信学会

    Presentation date: 2004.03

  • 拡張された階層モデルにおける予測アルゴリズムについて

    第25回情報理論とその応用シンポジウム  情報理論とその応用学会

    Presentation date: 2002.12

  • On the Channel Capacity of Universal Channel Coding

    Presentation date: 2002.12

  • On the evaluation of the achievable code length of Fixed-length coes

    2002 International Symposium on Information Theory and Its Applications 

    Presentation date: 2002.10

  • パラメータが時間変化する情報源とその符号化に関する一考察

    電子情報通信学会情報理論研究会  電子情報通信学会

    Presentation date: 2001.07

  • ユニバーサル符号における固定長符号の誤り率と可変長符号におけるオーバーフロー確率について

    第23回情報理論とその応用シンポジウム  情報理論とその応用学会

    Presentation date: 2000.11

  • Ziv-Lempel符号の冗長度に関する一考察

    電子情報通信学会情報理論研究会  電子情報通信学会

    Presentation date: 2000.07

  • On the variance and the probability of length overflow of lossless codes

    IEEE

    Presentation date: 2000.06

  • 符号長の分散とオーバーフロー確率について

    第22回情報理論とその応用シンポジウム  情報理論とその応用学会

    Presentation date: 1999.12

  • CELP音声符号化方式のランダム駆動信号に関する一考察

    電子情報通信学会情報理論研究会  電子情報通信学会

    Presentation date: 1999.07

  • An Approximation Algorithm of Bayes Coding for FSMX Sources

    1998 International Symposium on Information Theory and its Applications  情報理論とその応用学会

    Presentation date: 1998.10

  • ベイズ符号化法におけるメモリの問題点に関する一考察

    第20回情報理論とその応用学会  情報理論とその応用学会

    Presentation date: 1997.12

  • メモリに制限がある場合のベイズ符号化法について

    電子情報通信学会情報理論研究会  電子情報通信学会

    Presentation date: 1996.07

▼display all

Specific Research

  • 情報スペクトル理論に基づく不完全データを伴う仮説検定問題に関する基礎的研究

    2021  

     View Summary

    本研究は情報理論で近年発展している情報スペクトル理論を様々な問題に適用することを目標としたものである.特に,2021年度は確率構造が未知の状況における仮説検定問題を対象とし,誤り指数の解析を行った.情報理論における代表的な仮説検定問題の解析対象に,第一種の誤り確率が漸近的に一定値以下になるもとでの,第二種の誤り確率の誤り指数の導出がある.2021年度は二つの一般情報源に対してこのデータにノイズが混入する状況を通信路を用いてモデル化し,このもとでの誤り指数の解析を行った.

  • 確率構造が未知の乱数生成問題に対する情報スペクトル的アプローチ

    2020  

     View Summary

    本研究は情報理論で近年発展している情報スペクトル理論を様々な問題に適用することを目標としたものである.特に,2020年度は確率構造が未知の状況における乱数生成問題を対象とした.情報理論における代表的な乱数生成問題としては,任意の与えられた確率分布を一様乱数を用いて近似する問題(RESOLVABILITY問題)および,一様乱数から任意の確率分布を近似する問題(INTRINSIC RANDOMNESS問題)の二つがある.いずれの問題においても重要な指標は,確率分布の近似尺度と一様乱数のサイズである.確率分布の近似尺度としては従来変動距離やKullback-Leibler距離などがあるが本研究ではこれをより一般的なf-ダイバージェンスまで拡張し,その上で,目的とする確率分布と作成した確率分布の間のf-ダイバージェンスが一定値以下になるもとでの一様乱数サイズについて分析することが目標となる.2020年度はResolvability問題における最適一様乱数サイズについて,従来得られている表現と異なる数量で評価できることが分かった.また同様の考えをIntrinsic Randomness問題に対して適用可能であることも分かった.今後この研究を発展させて確率構造が未知のIntrinsic Randomness問題について調査する.

  • ユニバーサル予測問題に対する情報スペクトル的アプローチ

    2019  

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    本研究は情報理論で近年発展している情報スペクトル理論をユニバーサル予測問題に適用することを目標としたものである.本年度はその前準備として任意の確率分布を一様乱数を用いて近似する問題を考えた.この問題は情報源resolvability問題と呼ばれている.情報源resolvability問題の近似尺度として従来変動距離やKullback-Leibler距離などがあるが本研究ではこれをより一般的なf-ダイバージェンスまで拡張し,その上で情報源resolvability問題と情報源符号化問題の関係について考察した.これらの成果は今後論文誌に投稿予定である.

  • データ伝送・保存における高圧縮無杢符号化に関する研究

    2002  

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    本研究では無歪データ圧縮符号の性質に関して評価を行った.無歪データ圧縮符号は通常平均符号長を用いて評価されており,その評価基準の下では最適な符号が提案されている.平均符号長はあくまで平均を評価しているためひとつの情報系列を符号化した際にその符号長が短くなるという保証はない.その様な視点から近年オーバーフロー確率という評価基準が提案された.これは符号長がある値より長くなってしまう確率を評価したものである.本研究では,このオーバーフロー確率についてまずオーバーフロー確率が最小になる符号を提案し,それを用いてオーバーフロー確率が最小になる限界を評価した.また,平均符号長の意味で最適な符号のオーバーフロー確率を評価した.これらの成果は今後論文誌に投稿予定である.

 

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Committee Memberships

  • 2022.01
    -
    Now

    IEEE Information Theory Society Japan Chapter  Vice Chair

  • 2018.06
    -
    Now

    電子情報通信学会  和文論文誌A編集委員

  • 2018.06
    -
    Now

    IEICE  Associate Editor (EA)

  • 2015.05
    -
    2021.05

    電子情報通信学会 情報理論研究専門委員会委員

  • 2018.01
    -
    2019.12

    IEEE Information Theory Society Japan Chapter  Secretary

  • 2015.06
    -
    2017.05

    電子情報通信学会 コミュニケーション委員会 委員

  • 2015.05
    -
    2017.05

    電子情報通信学会 基礎・境界ソサイエティ特別委員

  • 2014.05
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    2015.05

    電子情報通信学会 情報理論研究専門委員会幹事補佐

  • 2013.05
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    2015.05

    電子情報通信学会 情報理論とその応用サブソサイエティ委員

  • 2012.05
    -
    2014.05

    電子情報通信学会 情報理論研究専門委員会幹事

  • 2011.05
    -
    2012.05

    電子情報通信学会 代議員(互選)

  • 2009.05
    -
    2011.05

    電子情報通信学会 基礎・境界ソサイエティ 庶務幹事

  • 2009.05
    -
    2011.05

    電子情報通信学会 著作権管理委員会委員

  • 2006.04
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    2008.03

    情報理論とその応用学会 国際担当幹事

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Social Activities

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