Performance of a combined USBL positioning and communication system using S2C technology

Ultra-short baseline (USBL) positioning systems and reliable data transfer systems for application on underwater vehicles have recently attracted significant interest. However, contemporary USBL transceivers and underwater acoustic modems operate separately in time and/or in different frequency bands. This paper presents a technical solution blending positioning and communication modes. Physical implementation of a combined positioning and communication device has been built upon the Sweep Spread Carrier (S2C) technology. Due to deep integration of a USBL positioning system with an underwater acoustic modem, the USBL antenna and the modem (apart of sharing the electroacoustic circuit) use also the same acoustic signal to transfer information and estimate the position of signal's source. A significant advantage of such a combined positioning and communication system consists in its ability to simultaneously track transponder/AUV movements and exchange instant messages and payload data with the transponder/AUV, enabling real-time control and navigation of the AUV based on actual positioning data. The paper presents experimental accuracy of the USBL estimating range and bearing of moving transponders in shallow waters, as well as data transfer rates obtained during data exchange in channels with strong reverberation.