Date of Award

Summer 2008

Degree Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Electrical and Computer Engineering

First Advisor

Yaz, Edwin E.

Second Advisor

Schneider, Susan

Third Advisor

Richie, James

Abstract

In February 2003, the Federal Communications Commission released 3.1GHz to 10.6GHz (total bandwidth of 7.5 GHz), the so-called Ultra-Wide Band communications, for public use. Chaotic communication, which is a recently developed wideband communication technique, has many unique properties and shows a wide range of applicability in this field of application. A promising approach to chaotic communication is the Chaotic-Sequence Division Multiple Access, which can be realized by using different chaotic maps for different transceivers. In this scheme, the unique properties of the chaotic sequence, such as noise-like wide-bandwidth, self-synchronization, ease of implementation, mitigation of multi-path transmission fading, impulse-like autocorrelation and almost zero cross-correlation, make it very suitable for short distance data transmission. Current popular modulation techniques, such as Chaotic On-Off Keying, Correlation Delay Shift Keying, Differential Chaotic Shift Keying and Chaotic Shift Keying are all exclusively based on correlation techniques and require precise timing synchronization, which can be difficult to implement, and they also do not provide satisfactory bit error rate results. Since chaotic signals can be thought of as the state variables of nonlinear systems, nonlinear state estimation techniques provide important tools for the demodulation system. However, currently available Extended Kalman Filter based schemes do not give satisfactory bit error rate performance. In this thesis, by modeling by modulation as a nonlinear estimation problem and employing advanced nonlinear filtering techniques, we improve currently available nonlinear filtering based chaotic modulation/demodulation schemes and discuss their corresponding bit error rate performances for various levels of signal to noise ratio. Most importantly, we present a novel antipodal chaotic communication scheme, which shows superior bit error rate and channel capacity performance. We have used the Extended Kalman Filter, the State Dependent Riccati Equation Estimator and the Unscented Kalman Filter for joint state and parameter estimation, to present different methods for each communication scheme. Both theoretical analysis and computer simulation results are provided to show performance improvements. The improved chaotic communications techniques in this thesis can be used in future UWB applications.

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