Integrated acoustic communication and navigation for underwater vehicles provides dual functionality in a single system which reduces cost, size, power and potential acoustic interference. A combination of time and code division multiplexing is used to allow long baseline navigation and bidirectional communication for a number of vehicles operating simultaneously in the same area. The communication system uses multi-rate phase coherent modulation to maximize throughput for the uplink from a vehicle to a central node, and code-division multiple-access using a simple frequency-hopping scheme. The data rate and modulation methods are completely programmable and may be selected based on the application requirements and the propagation conditions present between the different vehicles in the network. While one or several vehicles may use time-multiplexed long-baseline (LBL) navigation, when the number of vehicles grows large, the time between fixes becomes unacceptably long. Thus in addition to LBL, a second mode of navigation is also available for use with swarms of vehicles such as the surf-zone crawlers proposed for mine counter-measure applications. This second mode employs navigation broadcasts initiated by the central controller and incorporates three additional fixed nodes that transmit in response. The time differences of arrival measured at the vehicle are used to determine its location.
Freitag et al. (Wed,) studied this question.