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Seminars 2020
| Title: | Innovation in Constrained Codes |
| Speaker: | Professor Kees Schouhamer Immink |
| Date: | 22 December 2020 |
| Time: | 5.00pm |
| Venue: | Zoom (ID and PW will be given upon registration) |
| Host: | Assistant Professor Kiah Han Mao |
| Abstract: | Constrained, or line, coding is a somewhat nebulous term which we may define by either inclusion or exclusion. A constrained code converts user data into a signal format which facilitates detection in the presence of channel impairments. It further caters for receiver timing on bit, codeword, and frame level. In virtually all recording systems, as well as communication systems, some data sequences are much more prone to error than others. A constrained system is defined by a constrained set of "good" or "allowable" sequences to be recorded or transmitted. Constrained coding focuses on the analysis of constrained systems and the design of efficient encoders and decoders that transform arbitrary user sequences into constrained sequences. Constrained coding has extensively been used since the advent in the 1950s of electronic storage devices. They find application in all hard disk, non-volatile memories, optical discs, such as CD, DVD and Blu-Ray Disc, and they are now projected for usage in DNA-based storage. The speaker surveys the theory and practice of constrained coding, tracing the evolution of the subject from its origins in Shannon’s classic 1948 paper to present-day applications in DNA-based data storage systems. Open problems and future research directions are addressed. Specifically, he will discuss spectral shaping, run-length limited, two-dimensional, and Pearson codes. View Seminar Recording |
| Title: | Shannon's Information Measures and Markov Structures |
| Speaker: | Professor Raymond W. Yeung |
| Date: | 15 December 2020 |
| Time: | 5.00pm |
| Venue: | Zoom (ID and PW will be given upon registration) |
| Host: | Assistant Professor Kiah Han Mao |
| Abstract: | Originally studied in statistical physics, Markov random fields find applications in statistics, image processing, and in recent years social networks and big data. This talk is about Markov structures related to Markov random fields and their information-theoretic characterizations. In the 1990’s, the theory of I-Measure was developed as a full-fledged set-theoretic interpretation of Shannon’s information measures. In the first part of the talk, we give an overview of this theory. Then we discuss a set of tools developed on the I-Measure that is most suitable for studying a special Markov structure called full conditional mutual independence (FCMI), which turns out to be a building block for Markov random fields. One application of these tools is to show that the I-Measure of a Markov chain (a special case of a Markov random field) exhibits a very simple structure and is always nonnegative. In the second part of the talk, we discuss some recent results along this line: i. the Markov structure of a subfield of a Markov random field; ii. the Markov chain being the only Markov random field such that the I-Measure is always nonnegative; iii. how to construct information diagrams for Markov random fields. View Seminar Recording |
| Title: | The Information Bottleneck: A Unified Information Theoretic View |
| Speaker: | Professor Shlomo Shamai |
| Date: | 8 December 2020 |
| Time: | 5.00pm |
| Venue: | Zoom (ID and PW will be given upon registration) |
| Host: | Assistant Professor Kiah Han Mao |
| Abstract: | This presentation focuses on connections between relatively recent notions and variants of the Information Bottleneck and classical information theoretic frameworks, such as: Remote SourceCoding; Information Combining; Common Reconstruction; The Wyner-Ahlswede-Korner Problem; The Efficiency of Investment Information; CEO Source Coding under Log-Loss, Hypothesis Testing Error Exponent and others. We overview the upink Cloud Radio Access Networks (CRAN) with oblivious processing, which is an attractive model for future wireless systems and highlight the basic connections to distributed Gaussian information bottleneck framework. For this setting, the optimal trade-offs between rates (i.e. complexity) and information (i.e. accuracy) in the discrete and vector Gaussian schemes is determined, taking an information-estimation viewpoint. Further, the performance cost of the simple 'oblivious' universal processing in CRAN systems is exemplified via novel bounding techniques. View Seminar Recording |
| Title: | Arıkan meets Shannon: Polar codes with asymptotically fast convergence to channel capacity |
| Speaker: | Professor Venkatesan Guruswami |
| Date: | 1 December 2020 |
| Time: | 9.00am |
| Venue: | Zoom (ID and PW will be given upon registration) |
| Host: | Assistant Professor Kiah Han Mao |
| Abstract: | We establish a constructive version of Shannon’s noisy coding theorem for binary codes, with information rate converging near-optimally fast to channel capacity as a function of code length. Specifically, let W be an arbitrary binary-input memoryless symmetric channel with Shannon capacity I(W), and fix any delta > 0. We construct binary linear codes of length N and rate I(W) - O(N^{-0.5+delta}) that enable reliable communication on W with efficient encoding and decoding. Previously such a construction was only known for the erasure channel. An inverse square-root rate of convergence to capacity is information-theoretically the best possible, and matches the non-constructive bounds implied by Shannon's theorem. Our codes are a variant of Arıkan's celebrated polar codes. We employ multiple carefully constructed local kernels in the recursive construction of polar codes, one for each intermediate channel that arises in the decoding. A key technical ingredient in the analysis is a strong converse to the noisy coding theorem that shows extreme unpredictability of even a single message bit when communicating via random linear codes at rates just above capacity. Based on joint work with Andrii Riazanov and Min Ye View Seminar Recording |
| Title: | Physical Layer Security in Wireless Networks |
| Speaker: | Professor H. Vincent Poor |
| Date: | 24 November 2020 |
| Time: | 9.00am |
| Venue: | Zoom (ID and PW will be given upon registration) |
| Host: | Assistant Professor Kiah Han Mao |
| Abstract: | The increasing deployment of wireless systems poses security challenges in emerging dynamic and decentralized networks consisting of very large numbers of low-cost and low-complexity devices. Over the last two decades alternative/complementary means to secure data exchange in wireless settings have been investigated in the framework of physical layer security (PLS), addressing jointly the issues of reliability and secrecy. PLS takes advantage of the inherent randomness of wireless communication channels and/or the unclonability of hardware fabrication processes, to harvest entropy and deliver authentication, confidentiality, message integrity, and privacy in demanding scenarios. In this talk, we review these issues from an information theoretic security perspective. PLS relies on information theoretic proofs of (weak or strong) perfect secrecy, a notion first introduced by Shannon in 1949. As such, PLS systems cannot be “broken” irrespective of the adversarial computational power, i.e., the proofs do not rely on any assumptions regarding the hardness of particular families of algebraic problems. There are some fundamental differences between information theoretic security and classical cryptography, and we will also discuss some of the pros and cons of each. View Seminar Recording |
| Title: | Random and deterministic dimension reduction in state-space systems. A geometric explanation of the reservoir computing phenomenon. |
| Speaker: | Professor Juan-Pablo Ortega |
| Date: | 3 July 2020 |
| Time: | 3.00pm – 4.00pm |
| Venue: | Zoom (ID and PW will be given upon registration) |
| Host: | Professor Bernhard Schmidt |
| Abstract | The last years have seen the emergence of significant interplays between machine learning, control theory, dynamical systems, and stochastic processes, with interesting applications in time series analysis and forecasting. The resulting techniques are based on the use of randomly generated state-space systems with cheap-to-estimate parameters and have revolutionized the way in which we learn and path-continue complex and high-dimensional dynamic processes. In this seminar, I will start by giving a short but self-contained overview of this body of work that is generically referred to as reservoir computing. In the second part, I will proceed by describing recent progress on two dimension reduction techniques for the kind of systems that are customarily used in this approach to machine learning. The first one has to do with finite-dimensional random projections of certain universal infinite-dimensional approximants that yield randomly generated state-affine systems with linear readouts that, more importantly, provide a deep geometric explanation of the reservoir computing phenomenon. Finally, we will discuss a second and purely deterministic approach that is an extension to this framework of the so-called “optimal reduction” method that I introduced with Tudor Ratiu twenty years ago in the context of symmetric Hamiltonian systems. |
| Title: | Combinatorial Game Theory |
| Speaker: | Dr Urban Larsson |
| Date: | 31 March 2020 |
| Time: | 2.30pm – 3.30pm |
| Venue: | SPMS-MAS-03-06, EC Room 1 |
| Host: | Dr Bei Xiaohui |
| Abstract: | We discuss the classical theory of combinatorial perfect information 2-player games, starting with Bouton’s Nim (1902) and the Sprague-Grundy theory (1930s) for impartial games. Berlekamp, Conway, Guy (1970-1980s) discovered that the class of partizan combinatorial games (such as Chess, Go and Checkers) is a partially ordered group, under the disjunctive sum operator, with large equivalence classes. Conway famously revealed that such games constitute a vast generalization of our standard number system (together with Knuth). We will review this development and learn a rough classification of rulesets according to their temperatures as being ``cold’’, ``tepid’’ or ``hot’’. |
| Title: | FinTech Seminar Series: From Traditional Career to becoming a FinTech Founder |
| Speaker: | Michele Ferrario (CEO & Co-founder of StashAway) |
| Date: | 6 February 2020 |
| Time: | 3.30pm – 4.30pm |
| Venue: | SPMS-MAS-03-06, EC Room 1 |
| Host: | Asst Prof Pun Chi Seng (Director of MSc in FinTech) |
| Abstract: | Traditional Career to FinTech Founder: Join StashAway’s Co-founder and CEO Michele Ferrario as he shares his own experience of starting out at McKinsey in Italy and New York, transitioning to private equity, starting in internet companies in Italy, Pakistan and Southeast Asia and then taking the jump to co-found a FinTech firm. You will learn one person’s experience of what it takes to make calculated risks, succeed in different work cultures, and endure the ups and downs of starting a business. |
| Title: | An open conjecture on colliding permutations |
| Speaker: | Professor Claudia Malvenuto |
| Date: | 4 February 2020 |
| Time: | 2.30pm – 3.30pm |
| Venue: | SPMS-MAS-03-06, EC Room 1 |
| Host: | Associate Professor Chan Song Heng |
| Abstract: | We call two permutations of the first n naturals colliding if they map at least one number to consecutive naturals. The notion has been introduced in 2006 by Jànos Korner and myself. We asked for the maximum number of pairwise colliding permutations of n. We conjectured that such maximum is assumed in the central binomial coefficient $\binom{n}{\lfloor n/2 \rfloor}$. Variations such as cyclic colliding permutations have been considered later (with Gerard Cohen), or graph-different permutations (with J.Korner and Gàbor Simonyi). I will give an account of the 'state of the art' on this still open conjecture. |
| Title: | FinTech Seminar Series: Frontiers of Financial Inclusion: Marketplace Lending |
| Speaker: | it Raikar (CEO & Co-founder of Validus Capital) |
| Date: | 16 January 2020 |
| Time: | 3.30pm – 4.30pm |
| Venue: | SPMS-MAS-03-06, EC Room 1 |
| Host: | Asst Prof Pun Chi Seng (Director of MSc in FinTech) |
| Abstract: | Marketplace Lending: Traditionally, banks have been the backbone small businesses relied upon to access financing. With the advent of FinTech and the emergence of online lending in recent years, innovators are disrupting traditional lending models by offering small businesses alternative options to access and easily secure financing. This session will focus on Marketplace Lending and how it has transformed SME financing. Learn how FinTech innovations can support SME financing, what key drivers of FinTech credit are, and how Marketplace Lending is helping to drive financial inclusion for SMEs in Southeast Asia. |
| Title: | Towards Optimal Secure Computation protocols |
| Speaker: | Akshayaram Srinivasan |
| Date: | 14 January 2020 |
| Time: | 10.00am –11.00am |
| Venue: | SPMS-MAS-03-07, EC Room 2 |
| Host: | Associate Professor Chan Song Heng |
| Abstract: | Secure computation allows a set of mutually distrusting parties to compute a joint function of their private inputs such that the parties only learn the output of the functionality and nothing else about the inputs of the other parties. Secure computation is one of the central primitives in cryptography that encompasses several cryptographic abstractions and has many practical applications. The seminal results from the 1980s showed that every efficiently computable functionality can also be computed securely. However, these protocols were prohibitively inefficient and could only be considered as feasibility results. One of the central problems in cryptography is to construct secure computation protocols that are optimal in all efficiency parameters. In this talk, I will give an overview of my recent works that make progress towards constructing such optimal secure computation protocols. |
| Title: | Enumeration of Simultaneous Core Partitions |
| Speaker: | Professor Jaebum Sohn |
| Date: | 14 January 2020 |
| Time: | 2.00pm – 3.00pm |
| Venue: | SPMS-MAS-03-06, EC Room 1 |
| Host: | Associate Professor Chan Song Heng |
| Abstract: | In this talk, we are concerned with (n, n+1, . . . , n+p)-core partitions. Amderberhan conjectured that the number of (n, n+1, n+2)-core partitions is same as the nth Motzkin number. This conjecture was proved by several authors. We give an alternative proof of this result by establishing a bijection between the set of (n, n+1, n+2)-core partitions and that of Motzkin paths of length n. Similarly, we give a bijection between the set of (n, n+1, . . . , n+p)-core partitions and that of Motzkin paths of length n with some restrictions. Also, we show the recurrence relation for the number of (n, n+1, . . . , n+p)-core partitions with certain restrictions. Moreover, we enumerate the number of (n, n+1, . . . , n+p)-core partitions with a specified number of corners. |