OFDM Transmission for Doubly Dispersive Underwater Acoustic Channels

Abstract

In this thesis, an OFDM simulator is designed based on the theory presented, and tested with a real underwater acoustic (UWA) channel. The UWA channel is analyzed and a simplified model is presented that holds under achievable conditions. The SOS model is developed for the UWA channel, and uses the stretched exponential function to model the Doppler power spectrum. The result is an SOS simulator which is then added to the OFDM simulator. The OFDM simulators are shown to have a very good performance under real, quasi-stationary UWA channels. OFDM theory is presented and then applied to the UWA channel to combat frequency-selectivity. OFDM transmission on UWA channels is analyzed in great detail, with special emphasis on how the Doppler effect distorts the signal. A complete model which shows the channel effects on the received signal is developed. This is followed by ICI parametrization and two methods of Doppler compensation.