Date of Award
Doctor of Philosophy (PhD)
Electrical and Computer Engineering
Dr. K. M. Wong
Wavelet Packet Division Multiplexing (WPDM) is a multiple signal transmission technique in which the message signals are waveform coded on wavelet packet basis functions for transmission. It has the advantage of a parallel transmission system, but the overlapping nature of such waveforms in time and frequency provides a bandwidth efficiency improvement over the Frequency Division Multiplexing (FDM), whilst their orthogonality properties ensure that the overlapping message signals can be separated by a signal correlation receiver. The interface caused by timing errors in the receiver is examined, and modeled as the information signal sequence filtered by interference filters. A design procedure which exploits the inherent degrees of freedom in the WPDM structure to mitigate the effects of timing error is introduced and a waveform which minimizes the energy of the timing error is introduced and a waveform which minimizes the energy of the timing error interference is designed. An expression for the probability of error due to the presence of Gaussian noise and timing error for the transmission of binary data is derived. The performance advantages of the designed waveform over standard wavelet packet basis functions are demonstrated by both analytical and simulation methods. The performance of WPDM in impulsive noise and Gaussian noise is analyzed, simulated, and compared with the performance of a commonly used serial transmission system, Time Division Multiplexing (TDM). The results support the instinct that WPDM as a parallel transmission system provides greater immunity to impulsive noise than TDM. The performance of WPDM in fading channels is analyzed, and the time domain equalization technique - Pilot Symbol Assisted Modulation (PSAM) - is applied to suppress the error floor which is common in digital communication with coherent reception in fading channels. The derivation and simulation show that in flat fading channels, the error floor in WPDM is suppressed as successfully as FDM with the PSAM, and the frequency of pilot symbols used in WPDM is less than that in FDM to acquire the sufficient channel estimation, thus the WPDM wastes less capacity and energy on pilot symbols than FDM. The analysis of WPDM in two-ray frequency selective fading channels with PSAM is done, and shows that error floor is also suppressed to some extent, but not as striking as for flat fading channels. The reason for this is revealed in the analysis. The bandwidth efficiency improvement of WPDM, its simple implementation, its greater immunity to impulsive noise, and its good performance in fading channels indicate that WPDM holds considerable promise as a multiple signal transmission technique.
Wu, Jiangfeng, "Wavelet Packet Division Multiplexing" (1998). Open Access Dissertations and Theses. Paper 2051.