Author

Geetha Varna

Publication Date

2014

Document Type

Dissertation/Thesis

First Advisor

Tahernezhadi, Mansour

Degree Name

M.S. (Master of Science)

Department

Department of Electrical Engineering

LCSH

Ultra-wideband devices||Orthogonal frequency division multiplexing||Wireless communication systems||Electrical engineering

Abstract

Traditional OFDM systems use Cyclic Prefix (CP) in front of an OFDM symbol to maintain orthogonality. Ultra Wide Band (UWB) systems use Multiband OFDM approach in implementing applications of Wireless Personal Area Network (WPAN). Federal Communications Commission (FCC) put some regulations on UWB to co-exist with other narrowband and spread spectrum users. MB-OFDM follows OFDM modulation scheme where CP is used but CP introduces a structure into the transmitter due to which the ripples are produced in Power Spectral Density (PSD). Because of this ripples, power back-off is required at the receiver which is as large as 1.5 dB. As an alternative to CP, Zero Padding (ZP) is used where a flat PSD is obtained which requires zero power back-off. Circular convolution in CP is a natural phenomenon but for ZP, Overlap and add method (OLA) is used to ensure circular convolution. The ZP length used for OLA method is fixed and equal to 32 samples according to ECMA-368. If timing synchronization estimation errors occur, fixed ZP length may cause Inter Symbol Interference (ISI). So, a variable ZP length is required to avoid ISI depending upon the current band. Hence, a Multi Band Timing Synchronization algorithm is proposed to achieve variable ZP length based on current band for OLA method. This method benefits large delay spread channels. Improvement in SNR is achieved at particular Bit Error Rate (BER) for large delay spread channels.

Comments

Advisors: Mansour Tahernezhadi.||Committee members: Lichuan Liu; Donald S. Zinger.

Extent

56 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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