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The Autonomous Underwater Vehicles (AUVs) industry is still awaiting its Henry Ford to bring to the market solutions that are well adapted to the challenge of underwater exploration. This will certainly be done by the advent of small connected drones equipped with small sensors and embedded devices, allowing AUVs to operate in a coordinated swarm, at a unit price so affordable that we can consider deploying hundreds, or even thousands simultaneously, to be able to observe the ocean with an instrument of a size finally adapted to its immensity. The scope of this work is to build a high performance and lowcost embedded device easy to mount onboard small AUVs and implementing energy-based spectrum sensing algorithms in order to detect targets underwater using acoustic waves. The principle of design, hardware architecture and real-time implementation of the acoustic signal processing chain are described in this paper. Simulations and sea experiments have been conducted successfully and qualified the performance of the realized system to detect acoustic pings underwater depending on the signalto-noise ratio (SNR). Moreover, this paper proposes methods to improve the measured detection range and accuracy.

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Underwater Acoustic Sensor Networks (UWASNs) consist of a variable number of autonomous sensors or vehicles that are deployed over a given area to perform smart sensing and collaborative monitoring tasks. In UWASNs, sensor localization plays a critical role. Motivated by the advent of embedded systems and their widespread adoption in localization, this paper presents the design and architecture of an autonomous embedded system, that uses acoustic signal to communicate underwater. The proposed architecture implements a set of embedded interfaces, such as interprocessor communication link and serial interfaces, which facilitates its integration with other systems. The implementation of a straightforward localization algorithms based on the Phase Difference and the Time of Arrival techniques is also described. The ability of the developed system to localize underwater sensors was tested during sea trials.