An Acoustic Complexity Index Sensor for Underwater Applications

Underwater communications exploit acoustic signals to interconnect embedded systems deployed for various scientific, environmental, industrial, or security tasks. The engineering of networked devices in underwater environment is today considered a critical research challenge. The propagation of acoustic waves in water is characterized by low, distance-dependent bandwidth with high latency, and multi-path effects, which make it necessary the design of novel system-level solutions, communication protocols, and algorithms specifically tailored for these types of applications. This paper describes a novel hardware-software sensing platform for computing a synthetic index developed for marine ecology studies, called the acoustic complexity index. Computing this index entails performing the fast Fourier transform of signals in the range of audio frequencies. The adoption of a centralized approach/architecture would entail the transmission of the signals toward a sink for their processing, severely impacting communication efficiency. The development of the proposed low-power sensing module enables to carry on the computation on board of remote nodes, which work as virtual sensors. This reduces the communication burden (of about five orders of magnitude) with a negligible energy overhead due to on board computation.