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Open Access Publications from the University of California

Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2016)

As the number of units in underwater sensor arrays grow, low-cost localization becomes increasingly important to maintain network scalability. Methods using ambient ocean noise are promising solutions because they do not require external infrastructure, nor expensive on-board sensors. Here we extend past work in stationary array element localization from correlations of ambient noise to a mobile sensor array. After obtaining inter-node distance estimates using ambient noise correlations, these distances can be used to determine a relative localization of an array of mobile underwater sensor platforms without introducing any external infrastructure or on-board localization sensors.

In this work we explore the effects of receiver mobility on inter-node distance estimation via correlations of ambient acoustic noise. Through analysis and simulation, we develop an exact solution along with a more tractable approximation to the peak amplitude of the time-domain Green's function between the two mobile receivers, which provides an estimate of their spatial separation. Here we demonstrate that the mobile noise correlation amplitude at the average time delay between the receivers can be modeled with the wideband ambiguity function of a single sound source. We then use this approximation to discuss selection of design parameters and their effects on the noise correlation function.

This work acts as a piece in the larger problem of infrastructure-free localization for mobile underwater sensor networks. Combining a relative localization from this method with the absolute positions of several units could provide an absolute localization of an entire array, without the need for external infrastructure.

    Cover page: Inter-node Distance Estimation for Subsurface Drifting Hydrophones Using Ambient Acoustic Noise
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2016)
    This paper presents a demonstration of ambient acoustic noise processing on a set of free floating oceanic receivers whose relative positions vary with time. It is shown that it is possible to retrieve information that is relevant to the travel time between the receivers. With thousands of short time cross-correlations (10 s) of varying distance, it is shown that on average, the decrease in amplitude of the noise correlation function with increased separation follows a power law. This suggests that there may be amplitude information that is embedded in the noise correlation function. An incoherent beamformer is developed, which shows that it is possible to determine a source direction using an array with moving elements and large element separation. This incoherent beamformer is used to verify cases when the distribution of noise sources in the ocean allows one to recover travel time information between pairs of mobile receivers.
      • Article
      • Peer Reviewed
      UC San Diego Previously Published Works (2017)
      This presentation describes a demonstration of ambient acoustic noise processing on a set of free floating oceanic receivers whose relative positions vary with time. We show that we are able to retrieve information that is relevant to the travel time between the receivers. With thousands of short time cross-correlations of varying distance, we show that on average, the decrease in amplitude of the noise correlation function with increased separation follows a power law. This suggests that there may be amplitude information that is embedded in the noise correlation function. We develop an incoherent beamformer, which shows that it is possible to determine a source direction using an array with moving elements and large element separation. We show how the noise correlation function varies in the presence of a boat with a known GPS trajectory, and how this information can be used recover the relative geometry of the deformable array. This work indicates that the relative geometry of an array can be estimated using only passive signals and the automatic identification system already present in many coastal communities.
        Cover page: Ambient noise correlations on a mobile, deformable array
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