Mode based model for high frequency underwater communication channels

Underwater environment is modeled as a bounded medium with the surface and bottom. Different acoustic models are used to model sound propagation in underwater environment. In this work a broadband mode based model, proposed for underground tunnels, is adapted for underwater environment and ray-mode analogy is studied in detail. In ray theory, the wave field is modeled as a sum of paths between the source and the receiver while in mode theory the wave field is the weighted sum of the normal modes. The model is developed to relate the group velocity of modes with the arrival time of the ray. It is shown that the modes can be grouped together to form a ray. For simulation, a simple underwater environment is considered with 50 m water depth, constant sound speed profile, flat bottom and source and receiver at 25 m. The analytical results are compared with BELLHOP and there is a good match in the arrival time of the two models. Lastly, the size of mode groups is studied by summing different number of modes and related it with the arrivals.