Introduction to factor graphs and message passing

Appuntamento nella Blue Room dell'Istituto TeCIP

Si terrà martedì 30 giugno 2015, alle ore 10.30, presso la Blue Room dell’Istituto di Tecnologie della Comunicazione, dell'lnformazione e della Percezione (TeCIP), il seminario sul tema "Introduction to factor graphs and message passing (and its application in the design of detector for communications)".

Il seminario sarà tenuto da Naga V. Irukulapati (Chalmers University of Technology, Göteborg) ed è aperto a tutti gli interessati.

Abstract

Graphical models such as factor graphs (FGs) allow a unified approach to a number of topics in coding, signal processing, machine learning, statistics, and statistical physics. An FG is generated based on a factorization of a function and the sum-product algorithm (SPA) is a message-passing algorithm on the FG with the aim of computing marginal posterior distributions. A wide variety of algorithms developed in artificial intelligence, signal processing, and digital communications can be derived as specific instances of the SPA, including the forward/backward algorithm, the Viterbi algorithm, the iterative turbo decoding algorithm, Pearl's belief propagation algorithm for Bayesian networks, the Kalman filter, and certain fast Fourier transform algorithms. In this presentation, I will start with basics about Bayesian inference, delve into the details of the FG and SPA and show how the messages can be used to compute the marginal distributions. At the end of the talk, an application of these concepts will be given with our proposed detector for fiber-optical communications, stochastic digital backpropagation, as a case study. FG and SPA have helped us to develop a near-optimal receiver and get closer to the fundamental performance limits of the fiber-optical channel.

Short Bio

Naga V. Irukulapati received the bachelors in technology (B.Tech) degree from Dhirubhai Ambani Institute of Information and Communication Technology (DA-IICT), India, in 2009, master studies in communication engineering program at Chalmers University of Technology in 2011 with "Sensor fusion for vehicular networks" topic as his master thesis. Immediately following the graduation, he joined the Fiber-Optic Communications Research Center (FORCE) as a Ph.D. student in the communication systems group at Chalmers. His current research focus is on receiver design for coherent optical communications with emphasis on mitigation of nonlinear effects and specifically on the design on optimal receivers. During his PhD, he has been to ETH Zurich to visit Prof. Loeliger, and to Coriant to work in a research lab.