الفهرس | Only 14 pages are availabe for public view |
Abstract Communicating underwater has been an area of interest of researchers, engineers, and practitioners alike. One of the main reasons for the slow rate of progress in this area is that the underwater acoustic channel is in general much more hostile-in terms of multipath effect, frequency selectivity, noise effect, and Doppler effect. The Underwater Acoustic Orthogonal Frequency Division Multiplexing (UWAOFDM) system is a well-known system that has recently became a preferred choice for underwater wireless communications. This thesis is presented to find a good solution to underwater communication problem. First, the thesis investigates a proposed implementation of Zero forcing (ZF) pre-equalization in UWA channels. It is known that the preequalization is highly effective in wireless communications. It mitigates the channel effects in an efficient manner. Due to the varying channel nature in UWA communications, it is expected that pre- equalization will be feasible in UWA channels. It will also mitigate the complicated nature of UWA channels. This channel suffers from channel variations, Doppler shift, attenuation, and multipath propagation. The implementation of the proposed pre-equalization and comparison with normal ZF equalization reveal a large degree of success of the proposed scheme. In fact, the frequency synchronization has a great importance in preserving the performance of the UWA-OFDM systems. The Carrier Frequency Offset (CFO) estimation can be blind or data aided. In this thesis, the Zadoff-Chu (ZC) sequences are used for OFDM synchronization in UWA communications, and they are compared with different data- Print to PDF without this message by purchasing novaPDF aided algorithms. We propose a low-complexity algorithm for CFO estimation based on ZC sequences. Also, a joint equalization and CFO compensation scheme for UWA-OFDM communication systems is presented. Simulation results demonstrate that the proposed CFO estimation algorithm allows estimation of the CFO accurately with a simple implementation in comparison with the traditional schemes. Moreover, the performance of the UWA-OFDM system can be preserved in the presence of frequency offset. |