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INTERFERENCE REDUCTION FOR MULTIACCESS
MULTICARRIER TRANSCEIVERS IN MOBILE ENVIRONMENTS
by
Layla Tadjpour
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Ful¯llment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(ELECTRICAL ENGINEERING)
May 2008
Copyright 2008 Layla Tadjpour
Object Description
| Title | Interference reduction for multiaccess multicarrier transceivers in mobile environments |
| Author | Tadjpour, Layla |
| Author email | tadjpour@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Electrical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2007-11-21 |
| Date submitted | 2008 |
| Restricted until | Restricted until 25 Mar. 2010. |
| Date published | 2010-03-25 |
| Advisor (committee chair) | Kuo, C. C. Jay |
| Advisor (committee member) |
Weber, Charles L. Kukavica, Igor |
| Abstract | High quality broadband services in mobile environments is essential for the next generation wireless communication system. Multiuser OFDM systems provide promising multiaccess techniques for high data rate transmission applications. However, in mobile environments, the Doppler spread effect or the carrier frequency offset (CFO) tend to destroy orthogonality among neighboring subcarriers and also among different users resulting in intercarrier interference (ICI) and Multiaccess interference (MAI) that severely degrade the performance of the system. Without efficient MAI and ICI suppression techniques in a mobile environment, one may resort to more complicated equalization and multiuser detection (MUD) techniques. As a result the receiver design for mobile multiuser OFDM systems is not simple. However, judicious code design in the transmitter of the multiuser OFDM systems, can either directly suppress MAI and ICI or help lower the complexity of multiuser detection techniques so that a low cost receiver is possible.; The code design problem to reduce MAI among multiple users is extensively studied in this work. First, the performance of a precoded multiuser OFDM (PMU-OFDM) system in a fast time-varying channel is evaluated and the criterion for the codeword design to suppress MAI and ICI is derived. In particular, it is proven that the use of M=2 even or the M=2 odd codewords of the M Hadamard-Walsh (HW) codes reduce the MAI due to the Doppler spread effect to a negligible amount. Later, the performance of two orthogonal codes for an MAI-free multicarrier CDMA (MC-CDMA) system in a CFO environment is studied in detail. It is shown that a proper subset of HW or carrier interferometry (CI) codewords achieves an MAI-free MC-CDMA system in the presence of CFO. Finally, it is demonstrated that employing CI codes for a fully-loaded MC-CDMA in a CFO environment leads to a sparse cross-correlation channel matrix that can be utilized to lower the complexity of the maximum likelihood, the parallel interference cancellation (PIC) and the decorrelating multiuser detectors. |
| Keyword | multicarrier CDMA; OFDM; interference cancellation; multiaccess interference; time varying channel; carrier frequency offset; multiuser detection |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Type | texts |
| Legacy record ID | usctheses-m1057 |
| Rights | Tadjpour, Layla |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Tadjpour-20080325 |
| Archival file | uscthesesreloadpub_Volume17/etd-Tadjpour-20080325.pdf |
Description
| Title | Page 1 |
| Full text | INTERFERENCE REDUCTION FOR MULTIACCESS MULTICARRIER TRANSCEIVERS IN MOBILE ENVIRONMENTS by Layla Tadjpour A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Ful¯llment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (ELECTRICAL ENGINEERING) May 2008 Copyright 2008 Layla Tadjpour |
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