  Underwater vehicles are utilized in various applications including underwater
data-collection missions. The tethered connection constrains the mission both
in distance traveled and number of vehicles that can run in the same area,
while the addition of acoustic communications onto the vehicles grants them
several functionalities. However, due to the low bandwidth of the underwater
acoustic channel-which leads to low data rates-and the time overhead imposed by
both the channel propagation delay and the processing delay by the acoustic
modems, efficient protocols are required. In this paper, an implicit
data-compression and transmission protocol is proposed to carry out
environmental monitoring missions such as adaptive sampling of physical and
chemical parameters in the water. In a semi-autonomous manner between the
vehicle and the control center, both sides keep silent in data transmission as
long as they can estimate and predict the actions of the other side, unless
environmental data and/or kinematic data are found to be unpredictable. Our
design puts the human in the loop to send high-level control commands.
Experiments were conducted using an autonomous vehicle with WHOI micro-modems
in the Raritan River, Somerset, Carnegie Lake in Princeton, and in the Marine
Park in Red Bank, all in New Jersey.
