ECE Colloquium - April 2, 2014
J. Rockey Luo, Associate Professor, ECE, Colorado State University
CoRE Building Lecture Hall
Coding Theory and Access Control for Distributed Wireless Networking
Classical network architecture assumes that communication optimization should be done at the physical layer. Data link layer only determines whether and when users should transmit packets. In a multiuser system, under the assumption that data link layer should efficiently schedule multiuser communication activities, classical channel coding has been focusing on coordinated communication scenarios where users jointly optimize their channel codes and communication parameters. As wireless networks are getting increasing complex and dynamic, scheduling the communication of a large number of users in a long time duration can be very difficult. Consequently, a significant proportion of messages in wireless networks are transmitted using distributed communication protocols. In these scenarios, users are not fully coordinated to optimize communication at the physical layer, and therefore data link layer should often get involved in communication adaptation. Unfortunately, not only that distributed communication is not well supported by classical channel coding theory at the physical layer, classical link layer model is also not able to support advanced communication adaptation due to the simple binary transmit/idle options of the users.
In this talk, we present a Shannon-style channel coding theory developed for distributed communication systems where users do not jointly design channel codes. We show that fundamental performance limitation of a distributed multiple access system can be characterized using an achievable region defined in a sense quite different from the classical ones. The new channel coding theory, which can indeed be viewed as an extension of the classical Shannon theory, enabled an enhanced physical-link layer interface where link layer users can now be equipped with more than two options to transmit their packets. At the data link layer, we formulate the distributed channel access problem as a non- coorperative game where each user optimizes an individual utility function. By assuming a general form of the utility functions, conditions under which the distributed channel access game possesses a unique Nash equilibrium is obtained. Simulation results show that when link layer users are provided with multiple transmission options, their behavior in distributed communication adaptation, as an outcome of the non-cooperative channel access game, tend to agree with the well known information theoretic understandings.
J. Rockey Luo received the Ph.D. degree in Electrical and Computer Engineering from University of Connecticut in 2002. From 2002 to 2006, he was a Research Associate with the Institute for Systems Research (ISR), University of Maryland, College Park. Since 2006, he has been with the Electrical and Computer Engineering Department of Colorado State University where he is currently an Associate Professor. His areas of research interests are communication networks, information theory, and signal processing.