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<p>The success of the Transformational Communications System depends on providing high quality communications  to the mobile user in any environment. A hurdle to this success is the urban Land Mobile Satellite Channel which  experiences frequent and extended deep signal fades due to shadowing by man-made structures. The problem is  exacerbated for the Communications-on-the-Move channel due to use of a directional antenna. This dissertation  evaluates available empirical test data, develops an improved channel model and investigates mitigation strategies  focused on improving channel throughput and latency. The improved channel model is developed using  continuous transmission mixed-Gaussian hidden Markov models and Expectation-Maximization parameter  estimation. The improved model provides a better match to empirical data than previous efforts. Two fade  mitigation strategies are examined. The first strategy involves modification of packet routing protocols. A  detailed, time-based network simulation is developed for performance assessment. Results show substantial  reductions in packet latency under a broad range of conditions. The second mitigation strategy is based on fade  prediction using real-time adaptive linear filters. Signal inputs from directional and non-directional antennas are  investigated. Initial results indicate a requirement for a high temporal resolution input signal.
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<br>Subjects: Telecommunication systems.; Land Mobile Satellite Channel; Transformational Communications System; Transformational Communications Architecture; Communications-on-the-move; Mobile Ad-hoc Network; Baum-Welch Algorithm; Least Resistance Routing; Neighbor protocol</div>
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Gillespie, Timothy T. A.</div>
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