Title page for ETD etd-02192004-165437


Type of Document Dissertation
Author Chongburee, Wachira
Author's Email Address wachira@vt.edu
URN etd-02192004-165437
Title Digital Transmission by Hermite N-Dimensional Antipodal Scheme
Degree PhD
Department Electrical and Computer Engineering
Advisory Committee
Advisor Name Title
Pratt, Timothy J. Committee Chair
Bostian, Charles W. Committee Member
Davis, William A. Committee Member
Sweeney, Dennis G. Committee Member
Thangjitham, Surot Committee Member
Keywords
  • Antipodal Scheme
  • Orthogonal Waveforms
  • Hermite Keying
  • Digital Modulation
  • Optimal Synchronization
  • N-dimensional PSD
Date of Defense 2004-02-11
Availability unrestricted
Abstract
A new N-dimensional digital modulation technique is proposed as a bandwidth efficient method for the transmission of digital data. The technique uses an antipodal scheme in which parallel binary data signs baseband orthogonal waveforms derived from Hermite polynomials. Orthogonality guarantees recoverability of the data from N simultaneously transmitted Hermite waveforms. The signed Hermite waveform is transmitted over a radio link using either amplitude or frequency modulation. The bandwidth efficiency of the amplitude Hermite method is found to be as good as filtered BPSK in practice, while the bit error rates for both modulations are identical. Hermite Keying (HK), the FM modulation version of the N-dimensional Hermite transmission, outperforms constant envelope FSK in terms of spectrum efficiency. With a simple FM detector, the bit error rate of HK is as good as that of non-coherent FSK. In a frequency selective fading channel, the simulation results suggest that specific data bits of HK are relatively secure from errors, which is beneficial in some applications. Symbol synchronization is critical to the system. An optimal synchronization method for the N-dimensional antipodal scheme in additive white Gaussian noise channel is derived. Simulation results confirm that the synchronizer can operate successfully at E/No of 3 dB.
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