Abstract
Due to the intense importance of underwater applications in military and commercial purposes, Underwater Acoustic Communication (UWAC) is an attracting research area. Very high propagation delay, path loss, and low bandwidth are the factors that challenged the acoustic waves in an underwater environment. Multi-input multi-output (MIMO) techniques are currently considered in UWAC to surpass the bandwidth limitation of the undersea channel. In this paper, the accomplishment of a MIMO in UWAC System highlighting both Line of Sight (LOS), i.e. the Rician fading and Non-Line of Sight (NLOS), i.e. the Rayleigh fading signal propagation, is assessed. Spatial Modulation technique is used, which helps in increasing the data rate in UWAC. It controls the spatial distribution of the energy caused by a signal in such a way that the single ocean channel sustains multiple parallel communication channels. The utilization of Zero Forcing (ZF) equalizer, which estimates the transmitted data proves the success of removing inter symbol interference (ISI). Matlab simulations are done for the UWAC system for values of LOS/NLOS. Because of various scattering effects in NLOS propagation, the error rate is considerably high when compared to that of the LOS propagation. Bit Error Rate (BER) values for the corresponding signal to noise ratio (SNR) are calculated.
Highlights
Nowadays, Underwater Acoustic Communications (UWAC) is an open research, which includes the present day expansion of human activities in undersea environments, i.e. environmental monitoring and offshore oil field exploration
Simulations in Matlab have been carried out for the channel model shown in Figure 3. 4-QAM spatial modulation is given at the transmitter which is a cost and complexity efficient, while at the receiver Zero Forcing (ZF) equalization is utilized to detect the transmitted data
For Non-Line of Sight (NLOS), i.e. the Rayleigh fading considers the multipath fading involved in UWAC
Summary
Underwater Acoustic Communications (UWAC) is an open research, which includes the present day expansion of human activities in undersea environments, i.e. environmental monitoring and offshore oil field exploration. Heavy energy consumption, large path loss, and low bandwidth have posed challenges for applying acoustic waves in underwater environment [8]. Three major factors that characterize acoustic wave propagation are attenuation, multipath propagation that varies along with time, and low sound speed. The signal may be constructive or destructive [10] Three factors that characterize the channel in UWAC are long multipath delay, high Doppler spread, and time-varying Doppler shift. This multipath delay is the main cause of Inter-Symbol Interference (ISI). Large area multi-path spread, Doppler shift, and background noise make the underwater environment much more complicated than a simple wireless channel. The design and implementation of high data rate UWAC are a major challenge
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