Study of probe signal bandwidth influence on estimation of coherence bandwidth for underwater acoustic communication channel

Abstract

A signal transmitted in a shallow Underwater Acoustic Communication (UAC) channel suffers from time dispersion due to the multipath propagation and the refraction phenomena. This causes intersymbol interference of the received signal and frequency-selective fading observed in its spectrum. Coherence bandwidth is one of the key transmission parameters used for designing the physical layer of a data transmission system to minimise the influence of time dispersion on the received signal. It can be calculated on the basis of the channel impulse response, measured with the use of the correlation method and frequency modulated signals or pseudorandom binary sequences. Such signals have a narrow, impulse-like autocorrelation function if considered in baseband. However, in the case of bandpass measurements, the influence of the probe signal on the estimate of the impulse response, and thus on the estimate of transmission parameters, is no longer negligible. The paper presents the results of an experimental study on probe signal bandwidth influence on estimation of coherence bandwidth. Simulations were carried out using UAC channel impulse responses measured in an inland reservoir.