Under-ice and open-water acoustic communication in the Fram Strait

Channel measurements and acoustic communication data are presented for field experiments in the Fram Strait. Four modulation schemes were tested in the 4-8 kHz band at a site where 80-90% of the sea surface was covered by drift ice. The channel was characterized by a small Doppler spread, but as the transmission range increased the delay spread became large (180 ms at 20 km). Similar experiments were performed at a second site, outside the seasonal ice zone. The delay spread was smaller than in the ice zone, but still sizeable, whereas the Doppler spread was much larger. These channel characteristics are reflected in the communication performance, where the picking order of the four schemes differs between sites.