Resource Allocation for Mobile Multiuser OFDM Systems

Prof. Brian L. Evans

Embedded Signal Processing Laboratory
Dept. of Electrical and Computer Engineering
The University of Texas at Austin


OFDM System Design Research


A downlink wireless system features a centralized basestation communicating to a number of users physically scattered around the basestation. The purpose of resource allocation at the basestation is to intelligently allocate the limited resources, e.g. total transmit power and available frequency bandwidth, among users to meet users' service requirements. Channel-aware adaptive resource allocation has been shown to achieve higher system performance than static resource allocation, and is becoming more critical in current and future wireless communication systems as the user data rate requirements increase.

In the first part of the talk, we consider resource allocation for the downlink of a mobile multiuser-OFDM system that enforces proportional data rate constraints among users. We formulate the problem assuming perfect channel state information (CSI) at the receiver and transmitter. We then propose a near-optimal algorithm achieving exact proportionality, and a lower complexity algorithm that achieves higher sum capacity with approximate proportionality. We also present computational complexity and memory usage results using a real-time DSP-based prototype implementation.

In the second part of the talk, we relax the perfect CSI assumption, and present high-performance OFDM channel prediction algorithms to overcome the feedback delay. Compared with previous algorithms, our approach has much lower mean-square error, while having the same order of complexity. Simulation results for an IEEE 802.16e system are presented.


Dr. Brian L. Evans is the Mitchell Professor of Electrical and Computer Engineering at The University of Texas at Austin. His research and teaching efforts are in embedded real-time signal and image processing systems. In signal processing, his research group is focused on the design and real-time software implementation of ADSL transceivers and multiuser OFDM systems, with the goal of maximizing connection rates for high-speed Internet access. In image processing, his group is focused on the design and real-time software implementation of high-quality halftoning for desktop printers, smart image acquisition for digital still cameras, and perceptual image hashing for authentication and databases. Dr. Evans has published over 140 refereed conference and journal papers. His B.S.E.E.C.S. (1987) degree is from the Rose-Hulman Institute of Technology, and his M.S.E.E. (1988) and Ph.D.E.E. (1993) degrees are from the Georgia Institute of Technology. From 1993 to 1996, he was a post-doctoral researcher in the Ptolemy project at UC Berkeley. He is the recipient of a 1997 US National Science Foundation CAREER Award.