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In this work a framework is presented for addressing the issue of intermittent communications faced by autonomous unmanned maritime vehicles operating at sea. In particular, this work considers the subject of predictive atmospheric signal transmission over multi-path fading channels in maritime environments. A Finite State Markov Channel is used to represent a Nakagami-m modeled physical fading radio channel. The range of the received signal-to-noise ratio is partitioned into a finite number of intervals which represent application-specific communications states. The Advanced Propagation Model (APM), developed at the Space and Naval Warfare Systems Center San Diego, provides a characterization of the transmission channel in terms of evaporation duct induced signal propagation loss. APM uses a hybrid ray-optic and parabolic equations model which allows for the computation of electromagnetic (EM) wave propagation over various sea and/or terrain paths. These models which have been integrated in the proposed framework provide a strategic and mission planning aid for the operation of maritime unmanned vehicles at sea., Presented at SPIE Defense, Security, and Sensing, DSS 2014, in Baltimore, MD on 6-8 May 2014 and published in SPIE Proceedings v9084: Unmanned Systems Technology XVI. Prepared in collaboration with the Aerospace Systems Design Laboratory, Georgia Institute of Technology, Atlanta, GA. The original document contains color images.

This report presents and demonstrates a methodology for analyzing the frequency diversity dependency of a transmitted signal as a function of evaporation duct heights. The integrated Advanced Propagation (APM) module is used to compute maritime signal propagation loss, and a Nakagami-m model is used to model the fading channel. Several approaches for evaluating intermittent communications in maritime environments were presented and demonstrated. The authors show how the Navy-validated APM in combination with an effective channel model can predict maritime communications. Using this approach, simulation results showing the impact of evaporation ducts' wideband frequency diversity, as well as communication links states are presented. These types of analyses have very important applications in mission planning, and are a promising solution that can provide enhanced communication autonomy in unmanned maritime vehicles., Prepared in cooperation with the Dept of Aerospace Engineering, Georgia Institute of Technology, Atlanta.