Communication Links for Spatially Distributed ASW Sensor Systems

The Navy intends to develop distributed fields of underwater sensors devoted primarily to ASW. These fields may include stationary nodes and/or mobile nodes, but will have the need to move data among the nodes in the field and to reconfigure the system to respond to an evolving threat situation. There are instances in which this network connectivity can be accomplished with hardwire links, but in the majority of cases, acoustic communication will be the preferred method. Our goal is to develop the infrastructure to support robust, clandestine network-wide data fusion and data transmission to the end user. Our Phase 1 proposal listed five requirements in the statement of work: 1. Develop the top-level protocols necessary to enable asynchronous, CDMA-based acomms, and refine the existing CDMA signaling to support these protocols. 2. Evaluate requirements for high data rate signaling. 3. Redesign the electronic and acoustic characteristics of the modem to support dual frequency operations (full duplex). 4. Develop the top level protocols necessary to support dual band signaling. 5. Evaluate the requirements for modem-based, in-situ signal processing and data fusion and identify algorithms to satisfy those requirements. Each of these issues were addressed in the Phase 1 study, but the emphasis quickly became the design of a new generation modem able to satisfy the requirements derived from our analyses. The current Benthos modem is the ATM 88x series, a successful and reliable tool which was developed over many years under SBIR, BAA, and IR&D funding. It is, by far, the most versatile acoustic modem available anywhere. However, the demand for acoustic communications is increasing at a rapid pace, and the capabilities of the existing infrastructure simply are inadequate for many of the new applications. The present ASW application is an ideal example: in order to support distributed sensors in an integrated network, a dual band telemetry system is required. However, the existing modem cannot provide this capability. In summary, the Navy requires autonomous underwater systems which can collect environmental data, provide surveillance functions, and provide C2 and data connectivity with the outside world.