Ocean acoustic impulse response measurement and characterization for ACOMMS performance prediction

Characterizing shallow water impulse response (SWIRM) is desirable when developing acoustic communications systems for the extremely reverberant ocean acoustic environment. The impulse response (IR) quantifies the sum of acoustic energy at a receiver for energy radiated from a source through diverse paths including direct paths, surface reflections, bottom reflections, and refractive paths between the source and receiver. The relatively shallow depths (less than 100 meters) and relatively long range (greater than 10 times the depth) of shallow water environment ensures that a significant portion of the acoustic energy has travelled through multiple paths off the ocean surface and bottom before reaching the receiver. Our research methodology characterized shallow water IRs using ocean experiments and computer simulations. We utilized acoustic hardware, data acquisition, analysis of ocean acoustic experimental data, adaptation of systems identification (SID) techniques for shallow water acoustic communications, development of an equalizer using SID (EQSID) as a digital communications model, and the testing of the EQSID model using noise and a Markov process for generating IRs. The analysis also utilized the systems integration of the EQSID communications model with the MMPE acoustic propagation model, into software tools collectively called Harbor Branch Oceanographic Acoustic Toolbox (HBOAT). HBOAT is continually evolving but includes the programs used in our SWIRM research for characterizing simulated shallow water IRs and using the IR characterization to predict the performance of the EQSID digital communications model