Perfect Reconstruction Conditions and Design of Oversampled DFT-Modulated Transmultiplexers

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by Pooyan Amini

A dissertation submitted to the faculty of The University of Utah in partial fulfillment of the requirements for the degree of

Doctor of Philosophy

Department of Electrical and Computer Engineering The University of Utah May 2013

Copyright © Pooyan Amini 2013 All Rights Reserved

The U n i v e r s i t y of Utah G r a d u a t e School

STATEMENT OF DISSERTATION APPROVAL

Pooyan Amini

The dissertation of

has been approved by the following supervisory committee members:

Behrouz Farhang-Boroujeny

Chair

01/31/2013 Date Approved

V. John Mathews

Member

02/01/2013 Date Approved

Rong-Ro ng Chen

Member

02/01/2013 Date Approved

Neal Patwari

Member

02/01/2013 Date Approved

Lawrence G. Zeng

Member

02/01/2013 Date Approved

and by the Department of

Gianluca Lazzi Electrical and Computer Engineering

and by Charles A. Wight, Dean of The Graduate School.

Chair of

ABSTRACT The demand for high speed communication has been increasing in the past two decades. Multicarrier communication technology has been suggested to address this demand.

Orthogonal frequency-division multiplexing (OFDM) is the most widely

used multicarrier technique.

However, OFDM has a number of disadvantages in

time-varying channels, multiple access, and cognitive radios.

On the other hand,

filterbank multicarrier (FBMC) communication has been suggested as an alternative to OFDM that can overcome the disadvantages of OFDM. In this dissertation, we investigate the application of filtered multitone (FMT), a subset of FBMC modulation methods, to slow fading and fast fading channels. We investigate the FMT transmitter and receiver in continuous and discrete time domains. An efficient implementation of FMT systems is derived and the conditions for perfect reconstruction in an FBMC communication system are presented. We derive equations for FMT in slow fading channels that allow evaluation of FMT when applied to mobile wireless communication systems. We consider using fractionally spaced per tone channel equalizers with different number of taps.

The numerical

results are presented to investigate the performance of these equalizers. The numerical results show that single-tap equalizers suffice for typical wireless channels. The equal­ izer design study is advanced by introducing adaptive equalizers which use channel estimation. We derive equations for a minimum mean square error (MMSE) channel estimator and improve the channel estimation by considering the finite duration of channel impulse response. The results of optimum equalizers (when channel is known perfectly) are compared with those of the adaptive equalizers, and it is found that a loss of 1 dB or less incurs. We also introduce a new form of FMT which is specially designed to handle doubly dispersive channels.

This method is called FMT-dd (FMT for doubly dispersive

channels). The proposed FMT-dd is applied to two common methods of data symbol orientation in the time-frequency space grid; namely, rectangular and hexagonal lattices. The performance of these meth