Why do Structured Codes help in Streaming Communication?

Professor Ashish Khisti
Assistant Professor, University of Toronto
Given on: Oct. 30th, 2014
Venue: Packard 101
Time: 4:15pm to 5:15pm


An increasing number of applications are streaming in nature. Information packets must be encoded and transmitted sequentially in real-time, and the receiver should reproduce the source stream under strict delay constraints. The study of fundamental limits and coding schemes in such communication systems is a fertile area of research. In this talk we will show how certain judiciously constructed structured codes can yield substantial gains over baseline schemes in streaming systems.

The first part of the talk will focus on channel coding over packet erasure channels. We will present a new family of streaming-codes that achieve significant performance gains over the practically relevant Gilbert-Elliott (GE) channel model. We will discuss how a certain “deterministic approximation” to the GE channel provides insights into the optimality of these codes. We will also discuss the operational significance of column-distance and column-span metrics in this setup, and show that our proposed codes achieve a near optimal tradeoff between these. In the second part of the talk we will study sequential coding of correlated sources over a packet erasure channel, using an information theoretic framework. We will discuss the performance of baseline schemes such as predictive coding and random binning, present a novel hybrid scheme, and discuss its optimality. If time permits I will also briefly discuss another recent work on broadcasting to multiple receivers with different demands over packet erasure channels.


Ashish Khisti joined the University of Toronto as assistant professor in September 2009, and presently holds the Canada Research Chair (Tier II) in Wireless Networks. He obtained his BASc degree in Engineering Sciences (Electrical Option) from the University of Toronto in 2002, and his SM and PhD degrees from the Massachusetts Institute of Technology (MIT), Cambridge, MA in Electrical Engineering and Computer Science. Prof. Khisti is a recipient of the Ontario Early Researcher Award from the province of Ontario and a Hewlett-Packard Innovation Research Prize. He currently serves as an Associate Editor of the IEEE Transactions on Communications, and is co-organizing a workshop on “Mathematical Coding Theory in Multimedia Steaming” at the Banff International Research Station in 2015.