Date of Award

3-2001

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Electrical and Computer Engineering

First Advisor

Michael A. Temple, PhD

Abstract

A proposed wavelet domain communication system (WDCS) using transform domain processing is demonstrated as having enhanced interference avoidance capability under adverse environmental conditions. The WDCS system samples the environment and uses the wavelet transform, to determine interference presence and time/scale location. A digital communication waveform (basis function) is subsequently designed in the wavelet domain to specifically avoid regions containing interference. The WDCS basis function is data modulated prior to transmission. Assuming perfect synchronization, the receiver replicates a locally generated basis function for correlating with the received signal and demodulating the data. The proposed system is modeled and simulation results are obtained using MATLAB. Bit error rate is the metric for analysis and performance comparisons. Relative to an equivalent DSSS, the WDCS provided bit error performance improvement in several different interference scenarios. The system also demonstrated comparable performance to a developmental TDCS while providing significant improvement in scenarios containing swept-tone interference. The system was evaluated using a signal bit energy-to- noise power level (E(beta)/N(omega) of 4.0 dB and interference energy-to-signal energy (I/E) ratios ranging from 0 dB to 16.0 dB. As defined, performance improvement metrics representing the ratio of DSSS-to-WDCS and DSSS-to-TDCS bit error rates were used for characterizing performance. For antipodal data modulation, the average (over all interference scenarios) DSSS-to-WDCS performance improvement was 12.4 dB, approximately equal to the DSSS-to-TDCS (comparable performance). For binary orthogonal data modulation, the average DSSS-to-WDCS improvement was 5.7 dB vs. 6.8 dB for the DSSS-to-TDCS comparison. These results indicate the proposed WDCS is a viable option for interference avoidance communications and worthy of further study.

AFIT Designator

AFIT-GE-ENG-01M-16

DTIC Accession Number

ADA391593

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