TIME-REVERSAL FOR TIME-VARYING ACOUSTIC COMMUNICATIONS AND A SIMPLE CHANNEL ESTIMATOR

Abstract

This research work studies and designs a proposed single-input-multiple-output (SIMO) OFDM communications system in MATLAB/Simulink environment, which discusses performance of time-reversal processing on a set of acoustic channels. The test channels for simulations are generated through Bellhop and a MATLAB script. This thesis also studies and analyzes a real experiment from literature using Bellhop to understand why time-reversal worked so well in that particular experiment. Finally, this work develops a basic channel estimator to study its performance in the designed Simulink based communication model.

OFDM signalling is used to accommodate equalization of frequency-selective fading allowing for simple channel equalization as well as the efficient modulation and demodulation via the fast Fourier transform. Repetition encoder/decoder of low rate is used as an error-control measure to combat interference and other adversities in acoustic channels. Multiple data streams are superimposed before transmission in order to enhance spectral efficiency. Iterative decoding and demodulation is applied to iteratively minimize the inter-carrier-interference caused due to the effects of Doppler in time-varying channels and to ultimately recover the original data streams.