The QUARP-Modem: A Quad-Channel Acoustic Research Platform for Underwater Communication and Tracking

This paper presents QUARP, a four-channel underwater acoustic platform that integrates communication, passive sensing, and source tracking within a unified architecture. The system adopts a dual-level design, combining a low-level microcontroller for real-time digital signal processing with a highlevel Linux-based processor for network management and data packing/unpacking. An open-source Python and MATLAB client library enables flexible deployments of QUARP in three operating modes: Modem, Hydrophone and Short Baseline Localization (SBL) system. In Modem mode, the platform acts as an acoustic underwater modem with a maximum communication rate of 400 bps. In Hydrophone mode, it enables passive sensing with a 300 kHz sampling rate. Finally, in SBL mode, the platform provides range estimation and Angle of Arrival measurements from a synchronized source. Experimental validation demonstrates the effectiveness of the proposed platform and its suitability for deployment in realistic underwater environments.