Thesis Defense of Marwane REZZOUKI, October 6, 2023

Marwane Rezzouki will defend his thesis on October 6, 2023, at 10:30 a.m., in the J-P.DOM lecture hall of the IMS Laboratory on the subject : “Towards Sustainable Fishing: A Hybrid System for Underwater Acoustic Communication and Localization Based on Chirp Signals”.

Over the last decades, underwater acoustic communication and localization systems have received much interest in diverse applications such as conducting ocean research, exploring natural resources, connecting autonomous underwater vehicles, and navigation. However, using acoustic waves that propagate at a low speed, approximately 1500 m/s, limits the bandwidth of communication. Besides, the underwater acoustic channel (UWA) is considered one of the most difficult mediums to use because of the severe transmission loss, multipath, high Doppler spread and shift, and important time and spatial variability. As a result, ensuring data link communication or localization in such channels requires the deployment of transmitters with high power, which could acoustically pollute the environment and participate in the migration of species. In this context, the purpose of this thesis is to enable a more sustainable and responsible fishing practice. We focused on addressing the issue of lost fishing nets in the ocean. Based on the waveform of the emitted signals, which is linear frequency modulation (chirp), we propose a hybrid acoustic system for communication and localization underwater. This system offers fishers the ability to enhance their fishing activities by establishing a reliable data link and facilitating the tracking of the fishing nets. This way, fishers will be able to find their nets if they get lost and avoid the creation of waste in the ocean.

The proposed system is based on a technique called differential chirp spread spectrum (DCSS) with additional processes at the receiver to overcome the challenging characteristics of the UWA channel. The DCSS modulation offers the ability to deploy a less disruptive network for marine animals since it is possible to demodulate received signals at a low level of signal-to-noise ratio (SNR). Moreover, multiple synchronized hydrophones are used at the receiver to calculate the time differential of arrival (TDOA) and then estimate the localization of the acoustic sources.