ahoi

Abstract

The recent development of small, cheap AUVs enables a plethora of underwater near-and inshore applications. Among these are monitoring of wind parks, detection of pollution sources, water-quality inspection, and the support of divers during disaster management. These tasks profit from online reporting, control, and AUV swarm interaction; yet they require underwater communication. Unfortunately, commercial devices are prohibitively expensive and typically closed-source, hampering their application in affordable products and research. Therefore, we developed the open-source 1 ahoi acoustic modem. It is (i) small enough to be carried by micro AUVs, (ii) consumes little enough energy to not diminish operation times of its host, (iii) comes at an attractive unit cost below $600, (iv) can reliably communicate at distances of 150 m and more, and (v) supports ranging without additional hardware. Due to its modular build, the modem can be customized and is suitable as research platform to analyze, e.g., MAC and routing protocols. We conducted extensive real-world studies and present results of communication range, packet reception rate, ranging accuracy, and efficient and reliable self-localization. Finally, we draw conclusions regarding acoustic communication, ranging, and localization with inexpensive and low-power devices that go beyond a particular device. Our study, hence, encompasses general insights, observations, and recommendations.

Low-Cost Underwater Swarm Acoustic Localization: A Review

“…Several modems provide software frameworks that provide software modules for implementing communication protocols, e.g. the ahoi modem [62] allows access to its firmware which enables both built-in Media Access Control (MAC) protocols and tests of tailored protocols. The open source EviNS framework [63] can be run directly on the Evologics acoustic modems' hardware where not only several MAC and routing protocols are available, but users can design own solutions on it.…”

“…The low-cost ahoi modem [62] is developed by researchers from Hamburg University of Technology. It has been used in field experiments in harbor area [31], [68], where in [68] the authors show that a moving BlueROV2 is localized with positioning error below 75 cm in an operation range below 30 m using an EKF for the position estimation and RTK-GPS as reference.…”

Localisation of Unmanned Underwater Vehicles (UUVs) in Complex and Confined Environments: A Review

“…Recently, the Ahoi-modem has been proposed as an inexpensive miniature approach to acoustic localisation and communication [58,59]. The cost is about 600 GBP per modem, of which the hydrophone's share is 400 GBP leaving 200 GBP to the open-source PCB design.…”

Wireless Remote Control for Underwater Vehicles

“…The market of HF modems is divided into two segments: low-rate acoustic modems and high-rate acoustic modems. While the former has a price below 2 kEUR and is suitable for low-rate (less than 200 bps) communication in shallow water up to a distance of 200 m [56][57][58], the latter has the same price as MF and LF acoustic modems (between 8 and 10 kEUR, depending on depth rate requirements) and can be used for sending a still-frame slide-show-like video feedback from an underwater vehicle [43,[59][60][61][62] to a control station, as they can perform transmissions with a bit rate of more than 30 kbps [29]. In this paper, we focus on this last type of modem in order to achieve the best performance possible despite the higher price.…”

“…Although the deployment of an LBL, that typically requires at least four baseline transponders plus the target transponder, is more expensive than the deployment of a USBL, it provides a higher positioning precision and is often used in oil and gas fields. In addition, the LBL transponder can either be specifically manufactured for positioning [105] or can be a regular acoustic modem with positioning capabilities [12,28,29,31,34,38,40,[55][56][57].…”