Tracking Multipath Structures in Shallow Water Acoustic Channels using Nonlinear Feature Representations

Abstract

We investigate geometric braids as a connected nonlinear feature representation to capture time-varying multipath activity for shallow water acoustic channels. These feature representations allow real-time continuous determination of dominant multipath within the channel delay spread, while keeping the identity of different and potentially intersecting multipath separate. While braids do not offer unique representations for individual delay taps, they can track and adapt non-uniformly across estimated acoustic channels. We aim to investigate the limitations of the braiding technique and the parameters that dictate the morphology of braids in the content of shallow water channel multipath. While the multipath activity can exhibit substantial time-variability, we focus on individual braids for each band and their evolution within the delay spread and time. Results will be shown and discussed through a few example underwater acoustic channels simulated using the BELLHOP model and a portion of the estimated channel from experimental field data collected during the SPACE08 experiment.