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Fitzhugh, Christopher I.

Electrical Engineering

2006

MS

This thesis investigates multipath fading of enclosed environments, specifically in a transportation bus and aircraft, for the deployment of a wireless sensor network. This multipath investigation was spurred by spectral data, obtained from two commercial passenger aircraft, that indicated a fading phenomenon more severe than predicted using the Rayleigh fading model. Current small-scale propagation models do not adequately represent the severe fading found in these two cavity environments. Hence, a new small-scale model is proposed based on the modification of the two-ray large-scale propagation model to define a new "worst-case" fading environment. The term hyper-Rayleigh is used throughout this thesis to describe this severe fading phenomenom. Examples of hyper-Rayleigh fading are presented and a possible explanation for this fading phenomenon is also provided through the development of the small-scale two-ray model. This work considers the scenario where both the transmitter and receiver are static. In an enclosed environment, the transmission is received over a few strong paths producing strong destructive interference, known as multipath fading. These interference patterns are a function of distance and wavelength, therefore, interference is dependent on the environment's geometry and the frequency of the signal. Spectral data collected in the 915 MHz, 2.4 GHz, and 5.8 GHz ISM bands is presented and analyzed to illustrate the multipath fading found in an enclosed environment. Diversity techniques are investigated to demonstrate ways to minimize the effects of hyper-Rayleigh fading. Empirical data is presented to illustrate the benefits of simple spatial or polarization diversity methods.