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Barritt, Brian JamesThe Modeling, Simulation, and Operational Control of Aerospace Communication Networks
Doctor of Philosophy, Case Western Reserve University, 2017, EECS - Computer Engineering
A paradigm shift is taking place in aerospace communications. Traditionally, aerospace systems have relied upon circuit switched communications; geostationary communications satellites act as bent-pipe transponders and are not burdened with packet processing and the complexity of mobility in the network topology. But factors such as growing mission complexity and NewSpace development practices are driving the rapid adoption of packet-based network protocols in aerospace networks. Meanwhile, several new aerospace networks are being designed to provide either low latency, high-resolution imaging or low-latency Internet access while operating in non-geostationary orbits -- or even lower, in the upper atmosphere. The need for high data-rate communications in these networks is simultaneously driving greater reliance on beamforming, directionality, and narrow beamwidths in RF communications and free-space optical communications. This dissertation explores the challenges and offers novel solutions in the modeling, simulation, and operational control of these new aerospace networks. In the concept, design, and development phases of such networks, the dissertation motivates the use of network simulators to model network protocols and network application traffic instead of relying solely on link budget calculations. It also contributes a new approach to network simulation that can integrate with spatial temporal information systems for high-fidelity modeling of time-dynamic geometry, antenna gain patterns, and wireless signal propagation in the physical layer. And towards the operational control of such networks, the dissertation introduces Temporospatial Software Defined Networking (TS-SDN), a new approach that leverages predictability in the propagated motion of platforms and high-fidelity wireless link modeling to build a holistic, predictive view of the accessible network topology and provides SDN applications with the ability to optimize the network topology and routing through the direct expression of network behavior and requirements. This is complemented by enhancements to the southbound interface to support synchronized future enactment of state changes in order to tolerate varying delay and disruption in the control plane. A high-level overview of an implementation of Temporospatial SDN at Alphabet is included. The dissertation also describes and demonstrates the benefits of the application of TS-SDN in Low Earth Orbiting (LEO) satellite constellations and High Altitude Platform Systems (HAPS).

Committee:

Frank Merat (Committee Chair); Rabinovich Michael (Committee Member); Daniel Saab (Committee Member); Mark Allman (Committee Member)

Subjects:

Aerospace Engineering; Computer Engineering; Computer Science

Keywords:

temporospatial; SDN; TS-SDN; aerospace; networks; satellites; LEO; NGSO; constellations; HAPS; high-altitude platforms; STK; wireless; mesh; networking; modeling; simulation; ns-3

Dawson, Hope C.Morphological variation and change in the Rigveda: The Case of -au vs. -ā:
Doctor of Philosophy, The Ohio State University, 2005, Linguistics
This dissertation is an investigation of a case of allomorphy between -au and in duals and i-stem locatives in the Rigveda. Traditional accounts of this alternation present a generalized, purportedly original distribution of preconsonantal -a: and prevocalic a:v. Cases that do not fit into this generalization, such as preconsonantal -au, are attributed to the date of a hymn’s composition or phonological factors. This study represents an exhaustive compilation of each form in the Rigveda (over 3000 total), and it reveals a complex interaction among several factors. The date of composition and the phonological environment do have an effect on this distribution, but they cannot account for the whole picture. Another factor in the variation is lexical idiosyncrasies in the patterning of the allomorphic endings. In both i-stem locatives and duals, different stems are shown to have different patterns of distribution. Even after controlling for chronological and phonological effects and for lexical idiosyncrasy, one additional factor must be considered: poetic effects and the influence of surrounding forms. The traditional generalizations must be called into question, and indeed no simple generalization can be proposed that is able to account for the data in this case: it is only in the interaction of various factors on certain forms in particular contexts that the explanation can be found. The variation found in the Rigveda is reflective of variation and change taking place in the living language at the time of composition. In this dissertation, I explore the synchronic and diachronic aspects of these variations and the factors affecting them, and I investigate the distribution of the -a: and -au allomorphs in the duals and i-stem locatives, as well as related categories, with particular regard to explaining how the data of the Rigveda itself can be accounted for.

Committee:

Brian Joseph (Advisor)

Keywords:

Sanskrit; Rigveda; Morphological constellations; allomorphy; duals; i-stem locatives