This dissertation presents unique and valuable insight into the analysis of packet-switched data communication systems. The research described in this dissertation examines performance characteristics of two types of packet-switched data communication systems. The first system to be analyzed operates in a parallel processing environment where cooperating processors independently perform assigned tasks. In this environment, the packet delay performance is dominated by queuing delays. The second type of system examined operates in a low earth orbit (LEO) satellite communications network environment. In this type of network, delay performance is affected by both queuing and propagation effects.
The objectives of this research are to study the effects of queuing and propagation on the average packet delay, the number of buffers required to implement the networks that interconnect the parallel processors, and the satellite resource utilization rates. For both types of communication systems, mathematical metamodels [Agr85] are developed to capture the effects on packet delay caused by incremental changes in network dependent parameters.
Part I of this research performs average packet delay and buffer cost comparisons of the augmented shuffle exchange network (ASEN) and the multistage cube (MSC) network. It is shown that the packet delay associated with the ASEN is between 20 and 25 percent lower than that of a similar sized MSC network. In addition to the delay benefits of the ASEN, network implementation cost savings for the ASEN are shown to be 9 to 16 percent lower than the MSC. Innovative mathematical design tools are developed and applied to the parallel processing interconnection network environment. These tools are used for predictive modeling of packet delay given network dependent parameters. The simple and concise models are shown to have predictive accuracy within 1 percent of the observed simulation delay results.
Part II of this research focuses on LEO satellite system communications. Six different constellations, providing whole-earth coverage are modeled and analyzed. The number of satellites within the constellations examined range from 36 to 77. The analysis of these LEO satellite systems consists of examining the packet delay characteristics of these dynamic systems as well how resource requests to the satellites are distributed. It is shown that when packet delay is the only design criteria, the differences in delay between the 36-satellite system and the 77-satellite are minimal and do not warrant the use the 77-satellite system over the 36-satellite system. The satellite resource utilization analysis captures the resource request load balancing characteristics of the systems. From a load balancing perspective, the 54-satellite system yields the best performance while the 36-satellite system the worst. A third unique aspect of the research presented in Part II is the application of metamodeling to the LEO satellite system environment. The metamodels developed reduce a complex 8-factor packet delay representation to simple, yet accurate, 2 and 3- factor relationships. These metamodel delay relationships are shown to have a predicted versus observed packet delay “best case” accuracy of 8 and 4 percent for the 3 and 2-factor models, respectively. Predicted versus observed packet delays are typically within 20 percent of agreement.
This research makes two contributions to the state-of-the-art knowledge in packet-switched communications system analysis. First, the metamodeling of interconnection networks and LEO systems are first of their kind. These models can allow for reduced simulation trials and more expeditious design decision making. The second contribution is the development of an integrated LEO satellite system model not seen in previously published research. This model can be used to further advance research in the LEO satellite system environment. / Ph. D.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/38269 |
| Date | 06 June 2008 |
| Creators | Raines, Richard A. |
| Contributors | Electrical Engineering, Davis IV, N.J., Bostian, Charles, Pratt, Timothy, Midkiff, Scott F., Abrams, Marc |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation, Text |
| Format | xix, 237 leaves, BTD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 31183660, LD5655.V856_1994.R356.pdf |
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