الفهرس 
Chapter 1 IntroductionOnly 14 pages are availabe for public view
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Abstract
The Underwater Acoustic (UWA) communication systems support low data rate, and have bad performance compared to traditional wireless systems. This is due to attenuation, ambient noise, water salinity, temperature, etc. In this work, transmission of acoustic signals in ocean environment adopts Orthogonal Fre-quency Division Multiplexing (OFDM) as a modulation technique due to its major benefits of spectral efficiency, good treatment to the equalization problem in fre-quency domain, and good treatment to the Inter-Symbol Interference (ISI) prob-lem. Unfortunately, It has Carrier Frequency Offset (CFO) problem at the receiver side. This thesis addresses the problems associated with the CFO, and also differ-ent equalization algorithms are presented for UWA channels with the goal of mit-igating some major impairments of these channels. Also, different challenges of the underwater channel such as temperature, salinity, and PH degree effects are investigated in the thesis. The work in this thesis can be divided into five main parts. The first part gives an overview of the underwater channel environment, and the UWA channel modeling is presented in order to predict the impulse response of the underwater channel. The second part gives a detailed overview of an OFDM system in UWA communication. This is followed by an overview of the CFO problem in UWA-OFDM systems and a study of different estimation and compen-sation algorithms. A proposed estimation algorithm for CFO estimations based on Zadoff-Chu (ZC) sequences is presented. The third part presents a proposed joint low-complexity equalization and CFO compensation algorithm for UWA systems based on banded-matrix approximation. The fourth part presents a joint Frequency Domain Equalization (FDE) and Low-Density Parity-Check (LDPC) coding algo-rithm in UWA-OFDM in order to improve performance. The fifth part presents a study of the challenges to underwater communication such as temperature, salin-ity, and the PH degree effects on the system performance.