Capacity and Reliability Function for Small Peak Signal Constraints

Dr. Vijay Subramanian

Motorola

Friday, February 14th, 3:00 PM, ENS 637

Abstract

The capacity and reliability function as the peak constraint tends to zero are considered for a discrete-time memoryless channel with peak constrained inputs. Prelov and van der Meulen showed that under mild conditions the ratio of the capacity to the squared peak constraint converges to one-half the maximum eigenvalue of the Fisher information matrix and if the Fisher information matrix is non-zero, the asymptotically optimal input distribution is symmetric antipodal signaling. Under similar conditions, it is shown in the first part of the talk that the reliability function has the same asymptotic shape as the reliability function for the power-constrained infinite bandwidth white Gaussian noise channel. The second part of the talk deals with Rayleigh-fading channels. For such channels, the Fisher information matrix is zero, indicating the difficulty of transmission over such channels with small peak constrained signals. Asymptotics for the Rayleigh channel are derived and applied to obtain the asymptotics of the capacity of the Marzetta and Hochwald fading channel model for small peak constraints, and to obtain a result of the type of Medard and Gallager for wide-band fading channels.

Biography

Dr. Vijay G. Subramanian received a B.Tech. degree from the Department of Electrical Engineering, Indian Institute of Technology, Madras in 1993, a M.S. degree in Electrical Engineering from the Indian Institute of Science, Bangalore in 1995, and a Ph.D. degree in Electrical Engineering from the University of Illinois at Urbana-Champaign in 1999. Since November of 1999 he has been with the Global Telecommunications Solutions Sector, Motorola, Arlington Heights working on resource allocation and channel-aware schedulers for wireless data. His research interests include information theory, communications, communication networks, wireless networks, and queuing theory.

A list of Wireless Networking and Communications Seminars is available at from the ECE department Web pages under "Seminars". The Web address for the Wireless Networking and Communications Seminars is http://signal.ece.utexas.edu/seminars