This paper discusses experimental and field evaluation results of differential multiple single carrier (MSC) modulation schemes for underwater acoustic communications (UWACs). UWACs suffer from severe doubly-selective channels and inter-carrier interference due to non-uniform frequency offset. In addition, assuming image data communications, UWACs have to improve frequency efficiency. In order to solve these issues, this paper proposes a wireless transmission scheme, which employ differential MSC modulation schemes. Next, this paper investigates parameters for 8kbps-UWACs and 64kbps-UWACs aiming at wireless control of autonomous underwater vehicle and image data communications, respectively. Finally, two experimental and field evaluation results in acoustic experimental pool and shallow-sea environment confirm that the UWAC MODEMs have excellent performance on severe doubly-selective channels.
