Date of Award

1-1-2012

Document Type

Dissertation

Degree Name

Ph.D.

Department

Electrical Engineering

First Advisor

Mohammad A. Matin

Keywords

Interleaved Frequency Division Multiple Access (IFDMA), Localized Frequency Division Multiple Access (LFDMA), Orthogonal Frequency Division Multiplexing (OFDM), Peak-to-Average- Power-Ratio (PAPR)

Abstract

Wireless communication has experienced an incredible growth in the last decade. Two decades ago,the number of mobile subscribers was less than 1% of the world's

population. As of 2011, the number of mobile subscribers has increased tremendously to 79.86% of the world's population.

Robust and high-rate data transmission in mobile environments faces severe problems

due to the time-variant channel conditions, multipath fading and shadow fading. Fading is the main limitation on wireless communication channels. Frequency selective interference and fading, such as multipath fading, is a bandwidth bottleneck in the "last mile" which

runs from the access point to the user. The "last mile" problem

in wireless communication networks is caused by the environment of free space channels through which the signal propagates. Orthogonal Frequency Division Multiplexing (OFDM)

is a promising modulation and multiplexing technique due to its robustness against multipath fading. Nevertheless, OFDM suffers from high Peak-to-Average- Power-Ratio (PAPR), which results in a complex OFDM signal. In this research, reduction of PAPR considering the out-of-band radiation and the regeneration of the time-domain signal

peaks caused by filtering has been studied and is presented. Our PAPR reduction was

30% of the Discrete Fourier Transform (DFT) with Interleaved Frequency Division Multiple Access (IFDMA) utilizing Quadrature Phase Shift Keying (QPSK) and varying the roll-off factor. We show that pulse shaping does not affect the PAPR of Localized Frequency Division Multiple Access (LFDMA) as much as it affects the PAPR of IFDMA. Therefore, IFDMA has an important trade-off relationship between excess bandwidth and PAPR performance, since excess bandwidth increases as the roll-off factor increases.

In addition, we studied a low complexity clipping scheme, applicable to IFDMA uplink and OFDM downlink systems for PAPR reduction. We show that the performance of the PAPR

of the Interleaved-FDMA scheme is better than traditional OFDMA for the uplink

transmission system. Our reduction of PAPR is 53% when IFDMA is used instead of

OFDMA in the uplink direction. Furthermore, we also examined an important trade-off relationship between clipping distortion and quantization noise when the clipping scheme

is used for OFDM downlink systems. Our results show a significant reduction in the PAPR and the out-of-band radiation caused by clipping for OFDM downlink transmission system.

Provenance

Recieved from ProQuest

Rights holder

Bader Alhasson

File size

131 p.

File format

application/pdf

Language

en

Discipline

Engineering, Electrical engineering

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