Robust Acoustic Communication With Underwater Vehicles In Noisy And Jammed Shallow Water Environments

Insit it ution This paper presents a protocol for acoustic communication with autonomous vehicles in shallow water environments, particularly in difficult areas such as harbors and marine work sites where direst point-to-point links are not sufficiently reliable. The protocol is a sequential decoding, code combining, Automatic Repeat :reQuest (ARQ) which makes efficient use of available store and forward transceivers placed in the area of operations. The protocol will attempt to maintain a single point-to-point link between the underwater platform and the data user whenever possible. If conditions deteriorate, the protocol will optimally take advantage of an intermediate store and forward transceiver to maintain uninterrupted communication. It is shown that the use of intermediate transceivers slows down the telemetry throughput slightly, power savings are significant, and a robust data link can be maintained in extremely noisy, reverberant and jammed environments. I will describe the point to point sequential decoding, code combining ARQ protocol for acoustic telemetry and present performance results obtained in Woods Hole harbor and Buzzards Bay. The second half of the presentation will discuss the effects of store and forward transceivers on throughput and power efficiency. I hope to incorporate results of ongoing experiments currently being performed in Buzzardls bay and address the hardware considerations incorporated in our modems and store and forward transceivers. Hardware requirements for the protocol will be presented and our existing hardware prototypes will be described and their performance analyzedi. It is found that while the store and forward protocol requires considerable software complexity, the hardware requirements for implementing the link are quite modest, and are easily met with commercially available digital signal processors.