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1	A selective automatic repeat request protocol for undersea acoustic links Kalscheuer, Jon M. 06 1900 (has links) Approved for public release, distribution is unlimited / A recent improvement to the Seaweb underwater wireless network was the implementation of a Selective Automatic Repeat Request (SRQ) mechanism. SRQ is a protocol implemented in the Seaweb link layer as a measure for mitigating unreliability inherent in the telesonar physical layer. In January 2004, an experiment was performed in St. Andrew's Bay, Panama City, Florida. The goal was to transmit large data files through the network, in accordance with a Naval Special Warfare need for imagery file telemetry. For three point-to-point test geometries, SRQ was tested with a noisy and variable physical layer. Through the incorporation of SRQ, the unreliability was overcome. A link-budget model calibrated with the sound channel data collected from the experiment establishes the benefit of a "SRQ gain." / Ensign, United States Navy Underwater acoustics Underwater acoustic telemetry SRQ Link-budget Acoustic communications FORCEnet Link layer Telemetry ARQ Telesonar Seaweb
2	Performance of acoustic spread-spectrum signaling in simulated ocean channels Pelekanos, Georgios N. 06 1900 (has links) Approved for public release, distribution is unlimited / Direct-Sequence Spread Spectrum (DSSS) modulation is being advanced as the physical-layer basis for Seaweb undersea acoustic networking. DSSS meets the need for channel tolerance, transmission security, and multi-user access. This thesis investigates the performance of subspace-decomposition blind-equalization algorithms as alternatives to RAKE processing of DSSS signals. This approach is tailored for superior performance in time-dispersive and frequency-dispersive channels characteristic of ocean acoustic propagation. Transmitter and receiver structures are implemented in Matlab and evaluated with a statistics-based model of a doubly spread channel with additive noise. Receiver performance is examined using Monte Carlo simulation. Biterror rates versus signal-to-noise ratio are presented for various multipath assumptions, noise assumptions, and receiver synchronization assumptions. / Lieutenant, Hellenic Navy Underwater acoustics Acoustic communications Underwater communications Underwater networks Undersea warfare Statistics-based channel modeling Direct-sequence spread spectrum Blind equalization Suspace composition DSSS DSCDMA Telesonar Seaweb

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A selective automatic repeat request protocol for undersea acoustic links

Performance of acoustic spread-spectrum signaling in simulated ocean channels