Time delay estimation of an acoustical signal in an ocean environment is a challenging problem because of the phase distortion of the received signal due to reflection or transmission by the sea surface and seabed.
In this thesis, the conventional time delay estimation methods based on the cross-correlation and Hilbert transform are reviewed, and an improved algorithm to enhance the accuracy of time delay is presented. The presented algorithm is based on the Hilbert transform of the envelope of the received signal. The advantage of this technique is demonstrated by the mathematical formulation and consequently, the numerical simulations are performed for the cases of various SNR(signal-to-noise ratio) conditions. The simulation results are compared with those of existing techniques such as cross-correlation, zero crossing of Hilbert transform.