A Study on Unpredictable Shallow Water Channel Behaviour by Various Multipath Patterns and Experimental Data Analysis

Abstract

In a view to frame robust communication in shallow water applications, multipath signal propagation is the prime concern. Multipath signal propagation is a common occurrence in shallow water acoustic channels. Though multipath patterns of transmitted signal are not explicitly seen, it is a main contributor for signal degradation. This fact motivated us to simulate possible multipath patterns and understand its influence in short range communication. In this paper, a three-path signal propagation model is presented, where besides line of sight (LOS) signal, other two non-line of sight (NLOS) signals contact any point on channel boundary to reach the receiver. When all multipath signals summed up, variation was noticed in the received signal of various multipath patterns. In order to validate, an experiment was carried out. A source was fixed in water-tank. and it periodically transmits low frequency acoustic signals which travel as pressure vibrations in the shallow water channel. At the other end receiver records them and channel behavior is investigated for close range. Experiment was repeated for input signals of various strengths and frequency. The simulation and measured results coincide and provide a basis to realize the prospective pattern geometry among various multipath patterns. This study reveals optimal input signal strength for better signal reception in the tough underwater channel which drives us towards high-quality communication established among the nodes in underwater networks.