Abstract
Nowadays, the increasing availability of commercial off-the-shelf underwater acoustic and non-acoustic (e.g., optical and electromagnetic) modems that can be employed for both short-range broadband and long-range low-rate communication, the increasing level of autonomy of underwater vehicles, and the refinement of their underwater navigation systems pave the way for several new applications, such as data muling from underwater sensor networks and the transmission of real-time video streams underwater. In addition, these new developments inspired many companies to start designing hybrid wireless-driven underwater vehicles specifically tailored for off-shore operations and that are able to behave either as remotely operated vehicles (ROVs) or as autonomous underwater vehicles (AUVs), depending on both the type of mission they are required to perform and the limitations imposed by underwater communication channels. In this paper, we evaluate the actual quality of service (QoS) achievable with an underwater wireless-piloted vehicle, addressing the realistic aspects found in the underwater domain, first reviewing the current state-of-the-art of communication technologies and then proposing the list of application streams needed for control of the underwater vehicle, grouping them in different working modes according to the level of autonomy required by the off-shore mission. The proposed system is finally evaluated by employing the DESERT Underwater simulation framework by specifically analyzing the QoS that can be provided to each application stream when using a multimodal underwater communication system specifically designed to support different traffic-based QoSs. Both the analysis and the results show that changes in the underwater environment have a strong impact on the range and on the stability of the communication link.
Highlights
Operated vehicles (ROVs) are unmanned underwater vessels typically operated through the so-called umbilical cable, composed of an optical fiber for a broadband low-latency communication link and a power line to supply the vehicle, making it possible to manage the system in real time
We evaluate the actual quality of service (QoS) achievable with an underwater wireless-piloted vehicle, addressing the realistic aspects found in the underwater domain, first reviewing the current state-of-the-art of communication technologies and proposing the list of application streams needed for control of the underwater vehicle, grouping them in different working modes according to the level of autonomy required by the off-shore mission
The acoustic modems selected for the wireless remote control designed in this paper are the Subnero WNC and the EvoLogics S2C HS, both equipped with an omnidirectional transducer, the former operating in the medium frequency (MF) bandwidth with long baseline (LBL) capabilities and the latter operating in the HF bandwidth
Summary
Operated vehicles (ROVs) are unmanned underwater vessels typically operated through the so-called umbilical cable, composed of an optical fiber for a broadband low-latency communication link and a power line to supply the vehicle, making it possible to manage the system in real time. In [14], we proved via simulation the possibility to exploit an underwater multimodal acoustic and optical link to pilot an inspection-class hybrid ROV/AUV, and in [15], we presented how the control range of the vehicle performing an AUV mission can be extended through a multihop acoustic network. Some offshore companies are currently developing commercial hybrid ROVs that can be piloted wirelessly for simple semiautonomous inspection operations [16,17] Both our system and the WHOI untethered ROV perform best in deep water, where optical signals can reach longer distances and acoustic links are less affected by multipath [18].
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