Investigation of shallow water communication channel with low frequency acoustic signals

Abstract

The channel behaviour is complex due to the uncertainty in underwater newlineenvironment. It leads to unreliable wireless communication under water. The newlinefactors disturbing acoustic signal propagation in such channels are multipath newlineeffect, attenuation due to signal absorption and spreading, diverse underwater newlinenoise and doppler effect. These issues create difficulty to establish newlinecommunication under water and need good design of system hardware to suit newlinethis environment. Thus, a basic survey of all research work in this domain is newlinenecessary to understand the channel characteristics. Thus, the objective of this newlineresearch work is to investigate the characteristics of shallow water newlinecommunication channel with low frequency acoustic signals. newlineSimulation work and experiments in underwater test bed at laboratory newlinewere performed to explore the channel behaviour. With MATLAB tool, newlinesignal communication through shallow water was studied theoretically for the newlinenatural signal propagation conditions along with the presence of bubble cloud newlineat the channel boundary. The impact of wind velocity on bubble height was newlinenoticed by the reduction in angle of signal reception. The improved signal newlinestrength was observed in simulation outcome when natural spreading of newlinesignal was included rather than common spreading factor in signal newlinepropagation. A theoretical study to bring out the significant multipath patterns newlinethat contribute to good signal reception by the transmission of low frequency newlineshift keying acoustic signal through shallow water channel was done. The newlinesimulation results are validated experimentally when signals of different newlinestrengths are communicated to various transmission ranges. newline