IT-Forum

IT-Forum: Topic TBA

Topic: 
TBA
Abstract / Description: 

Description TBA


 

The Information Theory Forum (IT-Forum) at Stanford ISL is an interdisciplinary academic forum which focuses on mathematical aspects of information processing. With a primary emphasis on information theory, we also welcome researchers from signal processing, learning and statistical inference, control and optimization to deliver talks at our forum. We also warmly welcome industrial affiliates in the above fields. The forum is typically held in Packard 202 every Friday at 1:15 pm during the academic year.

The Information Theory Forum is organized by graduate students Jiantao Jiao and Yanjun Han. To suggest speakers, please contact any of the students.

Date and Time: 
Friday, April 13, 2018 - 1:15pm
Venue: 
Packard 202

IT-Forum: Topic TBA

Topic: 
TBA
Abstract / Description: 

Description TBA


 

The Information Theory Forum (IT-Forum) at Stanford ISL is an interdisciplinary academic forum which focuses on mathematical aspects of information processing. With a primary emphasis on information theory, we also welcome researchers from signal processing, learning and statistical inference, control and optimization to deliver talks at our forum. We also warmly welcome industrial affiliates in the above fields. The forum is typically held in Packard 202 every Friday at 1:15 pm during the academic year.

The Information Theory Forum is organized by graduate students Jiantao Jiao and Yanjun Han. To suggest speakers, please contact any of the students.

Date and Time: 
Friday, March 16, 2018 - 1:15pm
Venue: 
Packard 202

IT-Forum: Topic TBA

Topic: 
TBA
Abstract / Description: 

Topic description TBA


 

The Information Theory Forum (IT-Forum) at Stanford ISL is an interdisciplinary academic forum which focuses on mathematical aspects of information processing. With a primary emphasis on information theory, we also welcome researchers from signal processing, learning and statistical inference, control and optimization to deliver talks at our forum. We also warmly welcome industrial affiliates in the above fields. The forum is typically held in Packard 202 every Friday at 1:15 pm during the academic year.

The Information Theory Forum is organized by graduate students Jiantao Jiao and Yanjun Han. To suggest speakers, please contact any of the students.

Date and Time: 
Friday, February 23, 2018 - 1:15pm
Venue: 
Packard 202

IT-Forum: BATS: Network Coding in Action

Topic: 
BATS: Network Coding in Action
Abstract / Description: 

Multi-hop wireless networks can be found in many application scenarios, including IoT, fog computing, satellite communication, underwater communication, etc. The main challenge in such networks is the accumulation of packet loss in the wireless links. With existing technologies, the throughput decreases exponentially fast with the number of hops.

In this talk, we introduce BATched Sparse code (BATS code) as a solution to this challenge. BATS code is a rateless implementation of network coding. The advantages of BATS codes include low encoding/decoding complexities, high throughput, low latency, and low storage requirement. This makes BATS codes ideal for implementation on IoT devices that have limited computing power and storage. At the end of the talk, we will show a video demonstration of BATS code over a Wi-Fi network with 10 IoT devices acting as relay nodes.


 The Information Theory Forum (IT-Forum) at Stanford ISL is an interdisciplinary academic forum which focuses on mathematical aspects of information processing. With a primary emphasis on information theory, we also welcome researchers from signal processing, learning and statistical inference, control and optimization to deliver talks at our forum. We also warmly welcome industrial affiliates in the above fields. The forum is typically held in Packard 202 every Friday at 1:15 pm during the academic year.

The Information Theory Forum is organized by graduate students Jiantao Jiao and Yanjun Han. To suggest speakers, please contact any of the students.

Date and Time: 
Friday, February 9, 2018 - 1:15pm
Venue: 
Packard 202

IT-Forum: Deterministic Random Matrices

Topic: 
Deterministic Random Matrices
Abstract / Description: 

Random matrices have become a very active area of research in the recent years and have found enormous applications in modern mathematics, physics, engineering, biological modeling, and other fields. In this work, we focus on symmetric sign (+/-1) matrices (SSMs) that were originally utilized by Wigner to model the nuclei of heavy atoms in mid-50s. Assuming the entries of the upper triangular part to be independent +/-1 with equal probabilities, Wigner showed in his pioneering works that when the sizes of matrices grow, their empirical spectra converge to a non-random measure having a semicircular shape. Later, this fundamental result was improved and substantially extended to more general families of matrices and finer spectral properties. In many physical phenomena, however, the entries of matrices exhibit significant correlations. At the same time, almost all available analytical tools heavily rely on the independence condition making the study of matrices with structure (dependencies) very challenging. The few existing works in this direction consider very specific setups and are limited by particular techniques, lacking a unified framework and tight information-theoretic bounds that would quantify the exact amount of structure that matrices may possess without affecting the limiting semicircular form of their spectra.

From a different perspective, in many applications one needs to simulate random objects. Generation of large random matrices requires very powerful sources of randomness due to the independence condition, the experiments are impossible to reproduce, and atypical or non-random looking outcomes may appear with positive probability. Reliable deterministic construction of SSMs with random-looking spectra and low algorithmic and computational complexity is of particular interest due to the natural correspondence of SSMs and undirected graphs, since the latter are extensively used in combinatorial and CS applications e.g. for the purposes of derandomization. Unfortunately, most of the existing constructions of pseudo-random graphs focus on the extreme eigenvalues and do not provide guaranties on the whole spectrum. In this work, using binary Golomb sequences, we propose a simple completely deterministic construction of circulant SSMs with spectra converging to the semicircular law with the same rate as in the original Wigner ensemble. We show that this construction has close to lowest possible algorithmic complexity and is very explicit. Essentially, the algorithm requires at most 2log(n) bits implying that the real amount of randomness conveyed by the semicircular property is quite small.


 

The Information Theory Forum (IT-Forum) at Stanford ISL is an interdisciplinary academic forum which focuses on mathematical aspects of information processing. With a primary emphasis on information theory, we also welcome researchers from signal processing, learning and statistical inference, control and optimization to deliver talks at our forum. We also warmly welcome industrial affiliates in the above fields. The forum is typically held in Packard 202 every Friday at 1:15 pm during the academic year.

The Information Theory Forum is organized by graduate students Jiantao Jiao and Yanjun Han. To suggest speakers, please contact any of the students.

Date and Time: 
Friday, February 2, 2018 - 1:15pm
Venue: 
Packard 202

IT-Forum: Recent Advances in Algorithmic High-Dimensional Robust Statistics

Topic: 
Recent Advances in Algorithmic High-Dimensional Robust Statistics
Abstract / Description: 

Fitting a model to a collection of observations is one of the quintessential problems in machine learning. Since any model is only approximately valid, an estimator that is useful in practice must also be robust in the presence of model misspecification. It turns out that there is a striking tension between robustness and computational efficiency. Even for the most basic high-dimensional tasks, such as robustly computing the mean and covariance, until recently the only known estimators were either hard to compute or could only tolerate a negligible fraction of errors.

In this talk, I will survey the recent progress in algorithmic high-dimensional robust statistics. I will describe the first robust and efficiently computable estimators for several fundamental statistical tasks that were previously thought to be computationally intractable. These include robust estimation of mean and covariance in high dimensions, and robust learning of various latent variable models. The new robust estimators are scalable in practice and yield a number of applications in exploratory data analysis.


 

The Information Theory Forum (IT-Forum) at Stanford ISL is an interdisciplinary academic forum which focuses on mathematical aspects of information processing. With a primary emphasis on information theory, we also welcome researchers from signal processing, learning and statistical inference, control and optimization to deliver talks at our forum. We also warmly welcome industrial affiliates in the above fields. The forum is typically held in Packard 202 every Friday at 1:15 pm during the academic year.

The Information Theory Forum is organized by graduate students Jiantao Jiao and Yanjun Han. To suggest speakers, please contact any of the students.

Date and Time: 
Friday, January 26, 2018 - 1:15pm
Venue: 
Packard 202

IT Forum: Tight regret bounds for a latent variable model of recommendation systems

Topic: 
Tight regret bounds for a latent variable model of recommendation systems
Abstract / Description: 

We consider an online model for recommendation systems, with each user being recommended an item at each time-step and providing 'like' or 'dislike' feedback. A latent variable model specifies the user preferences: both users and items are clustered into types. The model captures structure in both the item and user spaces, and our focus is on simultaneous use of both structures. We analyze the situation in which the type preference matrix has i.i.d. entries. Our analysis elucidates the system operating regimes in which existing algorithms are nearly optimal, as well as highlighting the sub-optimality of using only one of item or user structure (as is done in commonly used item-item and user-user collaborative filtering). This prompts a new algorithm that is nearly optimal in essentially all parameter regimes.

Joint work with Prof. Guy Bresler.

Date and Time: 
Friday, November 10, 2017 - 1:15pm
Venue: 
Packard 202

IT-Forum: Information Theoretic Limits of Molecular Communication and System Design Using Machine Learning

Topic: 
Information Theoretic Limits of Molecular Communication and System Design Using Machine Learning
Abstract / Description: 

Molecular communication is a new and bio-inspired field, where chemical signals are used to transfer information instead of electromagnetic or electrical signals. In this paradigm, the transmitter releases chemicals or molecules and encodes information on some property of these signals such as their timing or concentration. The signal then propagates the medium between the transmitter and the receiver through different means such as diffusion, until it arrives at the receiver where the signal is detected and the information decoded. This new multidisciplinary field can be used for in-body communication, secrecy, networking microscale and nanoscale devices, infrastructure monitoring in smart cities and industrial complexes, as well as for underwater communications. Since these systems are fundamentally different from telecommunication systems, most techniques that have been developed over the past few decades to advance radio technology cannot be applied to them directly.

In this talk, we first explore some of the fundamental limits of molecular communication channels, evaluate how capacity scales with respect to the number of particles released by the transmitter, and the optimal input distribution. Finally, since the underlying channel models for some molecular communication systems are unknown, we demonstrate how techniques from machine learning and deep learning can be used to design components such as detection algorithms, directly from transmission data, without any knowledge of the underlying channel models.

Date and Time: 
Monday, October 16, 2017 - 3:25pm to 4:25pm
Venue: 
Packard 202

Estimation of entropy and differential entropy beyond i.i.d. and discrete distributions

Topic: 
Estimation of entropy and differential entropy beyond i.i.d. and discrete distributions
Abstract / Description: 

Recent years have witnessed significant progress in entropy and mutual information estimation, in particular in the large alphabet regime. Concretely, there exist efficiently computable estimators whose performance with n samples is essentially that of the maximum likelihood estimator with n log(n) samples, a phenomenon termed "effective sample size enlargement". Generalizations to processes with memory (estimation of the entropy rate) and continuous distributions (estimation of the differential entropy) have remained largely open. This talk is about the challenges behind those generalizations and recent progress in this direction. For estimating the entropy rate of a Markov chain, we show that when the mixing time is not too slow, at least S^2/log(S) samples are required to consistently estimate the entropy rate, where S is the size of the state space. In contrast, the empirical entropy rate requires S^2 samples to achieve consistency even if the Markov chain is i.i.d. We propose a general approach to achieve the S^2/log(S) sample complexity, and illustrate our results through estimating the entropy rate of the English language from the Penn Treebank (PTB) and the Google 1 Billion Word Dataset. For differential entropy estimation, we characterize the minimax behavior over Besov balls, and show that a fixed-k nearest neighbor estimator adaptively achieves the minimax rates up to logarithmic factors without knowing the smoothness of the density. The "effective sample size enlargement" phenomenon holds in both the Markov chain case and the case of continuous distributions.

 

Joint work with Weihao Gao, Yanjun Han, Chuan-Zheng Lee, Pramod Viswanath, Tsachy Weissman, Yihong Wu, and Tiancheng Yu.

Date and Time: 
Friday, October 13, 2017 - 1:15pm
Venue: 
Packard 202

IT-Forum: Multi-Agent Online Learning under Imperfect Information: Algorithms, Theory and Applications

Topic: 
Multi-Agent Online Learning under Imperfect Information: Algorithms, Theory and Applications
Abstract / Description: 

We consider a model of multi-agent online learning under imperfect information, where the reward structures of agents are given by a general continuous game. After introducing a general equilibrium stability notion for continuous games, called variational stability, we examine the well-known online mirror descent (OMD) learning algorithm and show that the "last iterate" (that is, the actual sequence of actions) of OMD converges to variationally stable Nash equilibria provided that the feedback delays faced by the agents are synchronous and bounded. We then extend the result to almost sure convergence to variationally stable Nash equilibria under both unbiased noise and synchronous and bounded delays. Subsequently, to tackle fully decentralized, asynchronous environments with unbounded feedback delays, we propose a variant of OMD which we call delayed mirror descent (DMD), and which relies on the repeated leveraging of past information. With this modification, the algorithm converges to variationally stable Nash equilibria, with no feedback synchronicity assumptions, and even when the delays grow super-linearly relative to the game's horizon. We then again extend it to the case where there are both delays and noise.

In the second part of the talk, we present two applications of the multi-agent online learning framework. The first application is on non-convex stochastic optimization, where we characterize almost sure convergence of the well-known stochastic mirror descent algorithm to global optima for a large class of non-convex stochastic optimization problems (strictly including convex, quasi-convex and start-convex problems). A step further, our results also include as a special case the large-scale stochastic optimization problem, where stochastic mirror descent is applied in a distributed, asynchronous manner across multiple machines/processors. Time permitting, we will discuss how these results help (at least in part) clarify and affirm the recent successes of mirror-descent type algorithms in large-scale machine learning. The second application concerns power management on random wireless networks, where we use a game-design approach to derive robust power control algorithms that converge (almost surely) to the optimal power allocation in the presence of randomly fluctuating networks.

This is joint work with Nick Bambos, Stephen Boyd, Panayotis Mertikopoulos, Peter Glynn and Claire Tomlin.


 

The Information Theory Forum (IT-Forum) at Stanford ISL is an interdisciplinary academic forum which focuses on mathematical aspects of information processing. With a primary emphasis on information theory, we also welcome researchers from signal processing, learning and statistical inference, control and optimization to deliver talks at our forum. We also warmly welcome industrial affiliates in the above fields. The forum is typically held in Packard 202 every Friday at 1:15 pm during the academic year.

The Information Theory Forum is organized by graduate students Jiantao Jiao and Yanjun Han. To suggest speakers, please contact any of the students.

Date and Time: 
Friday, October 6, 2017 - 1:15pm
Venue: 
Packard 101

Pages

Subscribe to RSS - IT-Forum