Communication Links for Spatially Distributed ASW Sensor Systems

The Navy intends to develop distributed fields of underwater sensors devoted primarily to ASW, but possibly having extensions to a variety of disparate applications, such as environmental sampling. These fields may include stationary nodes, mobile nodes, or combinations of the two. The two features common to all are the need to move data among the nodes of the field, and to autonomously reconfigure the (ASW) focus of the system to respond to an evolving threat situation. It is anticipated that the ability of an individual sensor to perform the mission will be extremely limited, thus necessitating cooperative interactions among multiple sensors, and information fusing across the field. This, in turn, suggests that the sensors may have to be physically close, implying that large numbers of sensors will be required. There are instances in which the requisite network connectivity can be accomplished with hard-wired links, but in the majority of cases, acoustic communications (acomms) will be the preferred method. Although the acoustic channel is in a medium that often does not support rapid data transfers without excessive transmitter power, or which limits signaling to very short ranges, in this instance the acomms channel appears well matched to the short range separation among sensors. The Navy has, over many years, investigated the utility of many types of sensors for ASW purposes, including passive and active sonar, magnetics, and optics, among others. The Navy has also investigated many techniques for signal and data processing and analysis. Most have shown value under some circumstances, but not in others. Probably the most reliable, certainly the least difficult to use, is passive acoustics. This is also an undetectable approach which advances consideration of covert operation of the network. The preferred approach, however, is to develop both nodes and networks capable of supporting a variety of sensor and processing types. The problem we wish to address with this proposal is the development of low cost sensor nodes, each providing modest ASW performance within a limited physical range, with reliance on the network to refine the performance. We will describe a system in which the nodes may contain a variety of sensor types, with the nodes linked together by robust, clandestine acoustic communications supporting directed response to potential targets, with network-wide data fusion and transmission to an end-user. We anticipate that some portion of the work will be classified.