Recent experimental and physical modeling studies demonstrate that, as opposed to systems with smaller bandwidth, the Ultra-Wideband (UWB) channel exhibits frequency-dependent distortion of individual multipath components. This per-path distortion is particularly significant in outdoor UWB applications, where line-of-sight (LOS) or non-distorted reflected signals might not be available at the receiver (for example, in a canyon-like street). In these cases, the dominant propagation mechanisms involve shadowing (diffraction) and reflection by small objects (e.g. signs or lamp-posts). In this dissertation, a physical model is developed to investigate the position-dependent distortion of the UWB pulse. The results indicate that both the shadowed pulse and the reflected pulse (by small objects with dimensions bounded by the wavelengths present in the signal) are distorted. Design of optimal and suboptimal templates for the correlation receiver are investigated. The UWB pulses that accommodate robust template choice given by the transmit pulse shape for all propagation conditions and satisfy the FCC spectral mask for outdoor channels are identified. Finally, we analyze the frequency-dependent propagation gain of the UWB channels in various outdoor conditions. This knowledge quantifies the potential benefits of adapting the transmitted signal to the dominant propagation mechanism.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-08172006-145718 |
| Date | 22 August 2006 |
| Creators | Ma, Li |
| Contributors | Brian L. Hughes, Alexandra Duel-Hallen, Arne A Nilsson, Hans Hallen, Hamid Krim |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-08172006-145718/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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