Shallow water acoustic channel modeling and MIMO-OFDM simulations

The uniqueness of underwater acoustic (UWA) channel and features like limited bandwidth, multipath spread, severe Doppler Effect and transmission loss make the UWA communication more challenging and intricate. The use of multiple inputs multiple outputs (MIMO) increases the spatial diversity of the system and the bandwidth limitation issue is solved by Orthogonal Frequency Division Multiplexing (OFDM) due to its high spectral efficiency, whereas attenuation coefficient plays a key role in determining the transmission loss. UWA Channel capacity is highly influenced by the transducer spacing and the delay spread. A simple and brief MIMO UWA communication model is presented here to measure the transmission loss by analyzing different models, the spatial coherence by analyzing the effect of spacing between transducers, ambient noise effect, multipath effect and consequently increase the spatial diversity and spectral efficiency by using MIMO and OFDM for shallow water communication. The ambient noise effects are found using Wenz' model whereas three different models; Thorp's, Fisher & Simmons'(F&S) and Francois & Garrison's (F&G) models are analyzed and compared to find the attenuation coefficient of the acoustic signal. Multipath propagation of the signal is considered following the Ray Theory and a model proposed by Bouvet & Loussert is used to find multipath effect. Finally, the modeled underwater channels are used to simulate and analyze the performance of MIMO-OFDM communication.