Underwater acoustic channels are characterized by a severe spread in time and frequency. To provide a highly reliable communication environment in doubly spread channels for UWA communication, we have proposed Doppler-resilient orthogonal signal-division multiplexing (D-OSDM). D-OSDM is a combination of the OSDM technique and orthogonal multiple access, and it preserves orthogonality among data streams even after propagation through doubly spread channels. We have conducted test tank experiments and simulations, and have found that D-OSDM could cope well with time- and frequency-spread channels and that it achieves a good communication quality . In this talk, we will show some results of our first sea trial of D-OSDM, that was performed on 21 June, 2016 at Hashirimizu port, Kanagawa, Japan. In this trial, the transmitter is fixed on the harbor quay, and the receiver is fixed on a remotely-operated survey boat. Acoustic communication was performed by moving the boat to generate a severe spread in frequency. The experiments show that D-OSDM achieves a good communication quality even if the boat moves at a speed of about 1.5 kt.  Tadashi Ebihara and Geert Leus: Doppler-Resilient Orthogonal Signal-Division Multiplexing for Underwater Acoustic Communication, IEEE J. Ocean. Eng. 41 (2016) 408-427.
- Marine vessels
- Underwater sound