Braid representation of the shallow water acoustic channel to interpret temporal evolution of multipath arrivals

Abstract

We present a morphological representation of the underwater acoustic channel that employs geometric braids to gain real-time knowledge of the dominant multipath activity. The key idea is to incorporate braid manifolds in tandem with non-convex mixed norm optimization techniques to track the temporal evolution of multipath arrivals. Specifically, we focus on channel braids that manifest as rapidly fluctuating high-energy taps in the delay spread as well as the delay-Doppler scattering function. Multiple braids can also be topologically combined using braid operations to interpret oceanic phenomena such as caustics and surface wave focusing, among others. We present techniques for adaptively updating the channel braids and their overlap patterns to reflect the temporal evolution of the shallow water acoustic channel. We evaluate the performance of proposed morphological channel estimation technique in terms of the normalized prediction error and computational time. Results based on numerical channel simulations based on diverse oceanic and experimental conditions as well as experimental field data from the SPACE08 experiment will be presented.