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.