Space-Time Signaling in Multiple-Input Multiple-Output (MIMO) Wireless Systems

Mr. Robert W. Heath Jr.

Dept. of Electrical Engineering
Stanford University
Stanford, California

Monday, April 9th, 11:00 AM, ENS 637

Abstract

Multiple-input multiple-output (MIMO) antenna systems, i.e., wireless systems with multiple transmit and receive antennas, have high capacity both in theory and in practical implementations. Signaling, or coding, for MIMO systems, however, has been primarily limited to multiplexed signaling (for high data rate) and signaling (for high link reliability). In pratice, it is desirable to have the flexibility to distribute the available degrees of freedom between rate and reliability. Therefore, code designs that fall between multiplexed and diversity modes of operation are needed.

In this talk we present an overview of MIMO wireless systems. We provide an analysis of multiplexed and diversity transmission, which demonstrates that the optimal modulation scheme is dependent on the channel condition number and the data rate. We then introduce a new space-time code design for MIMO systems which bridges the gap between multiplexing and diversity. Our approach uses a flexible linear coding framework, proposed in the literature, which enables code designs for any combination number of transmit antennas, receive antennas, data rate, and diversity advantage. The proposed design criteria yield codes which perform well in terms of ergodic capacity as well as error probability. This is important because, as we illustrate, designs that perform well from an ergodic capacity point of view do not necessarily perform well from an error probability point of view. Examples are provided to illustrate performance improvements.

A list of Telecommunications and Signal Processing Seminars is available at from the ECE department Web pages under "Seminars". The Web address for the Telecommunications and Signal Processing Seminars is http://anchovy.ece.utexas.edu/seminars