First in-field Experiments with a "Bilingual" Underwater Acoustic Modem supporting the JANUS Standard

This paper presents the design, implementation, and in-field experimentation of a "bilingual" underwater acoustic modem with multi-hop networking capabilities. The designed system supports the use of the JANUS physical coding scheme and of a proprietary one. JANUS is an open, simple and robust digital coding technology currently in process to become a NATO standard. The Applicon SeaModem has been selected as the communication hardware to use and JANUS has been integrated into it. The designed system has also been interfaced with the SUNSET system which provides ad-hoc networking capabilities and the support for distributed cooperation. Additionally, SUNSET has been extended with a policy module allowing to switch between the different available communication schemes according to the network needs. In-lab experiments and in-field tests have been conducted to validate and evaluate the proposed system. A network of 4 underwater devices (three static nodes and one surface vehicle) was deployed and JANUS was used for initial contact and parameters negotiation to then switch to the proprietary communication scheme. Promising results were collected and several lessons were learnt. After the experiments a more efficient policy module has been designed and implemented and it will be tested in the next at-sea trial.