6 research outputs found
Enhancing wireless communication system performance through modified indoor environments
This thesis reports the methods, the deployment strategies and the resulting system
performance improvement of in-building environmental modification. With the
increasing use of mobile computing devices such as PDAs, laptops, and the expansion
of wireless local area networks (WLANs), there is growing interest in increasing
productivity and efficiency through enhancing received signal power. This thesis
proposes the deployment of waveguides consisting of frequency selective surfaces
(FSSs) in indoor wireless environments and investigates their effect on radio wave
propagation. The received power of the obstructed (OBS) path is attenuated
significantly as compared with that of the line of sight (LOS) path, thereby requiring
an additional link budget margin as well as increased battery power drain. In this
thesis, the use of an innovative model is also presented to selectively enhance radio
propagation in indoor areas under OBS conditions by reflecting the channel radio
signals into areas of interest in order to avoid significant propagation loss.
An FSS is a surface which exhibits reflection and/or transmission properties as a
function of frequency. An FSS with a pass band frequency response was applied to an
ordinary or modified wall as a wallpaper to transform the wall into a frequency
selective (FS) wall (FS-WALL) or frequency selective modified wall (FS-MWALL).
Measurements have shown that the innovative model prototype can enhance 2.4GHz (IEEE 802.11b/g/n) transmissions in addition to the unmodified wall, whereas
other radio services, such as cellular telephony at 1.8GHz, have other routes to
penetrate or escape.
The FSS performance has been examined intensely by both equivalent circuit
modelling, simulation, and practical measurements. Factors that influence FSS
performance such as the FSS element dimensions, element conductivities, dielectric
substrates adjacent to the FSS, and signal incident angles, were investigated. By
keeping the elements small and densely packed, a largely angle-insensitive FSS was
developed as a promising prototype for FSS wallpaper. Accordingly, the resultant can
be modelled by cascading the effects of the FSS wallpaper and the ordinary wall (FSWALL) or modified wall (FS-MWALL). Good agreement between the modelled,
simulated, and the measured results was observed.
Finally, a small-scale indoor environment has been constructed and measured in a
half-wave chamber and free space measurements in order to practically verify this
approach and through the usage of the deterministic ray tracing technique. An initial
investigation showing that the use of an innovative model can increase capacity in
MIMO systems. This can be explained by the presence of strong multipath
components which give rise to a low correlated Rayleigh Channel. This research work
has linked the fields of antenna design, communication systems, and building
architecture
Abstracts on Radio Direction Finding (1899 - 1995)
The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography).
Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM.
The contents of these files are:
1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format];
2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format];
3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion
Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)
Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression
GSI Scientific Report 2009 [GSI Report 2010-1]
Displacement design response spectrum is an essential component for the currently-developing displacement-based seismic design and assessment procedures. This paper proposes a new and simple method for constructing displacement design response spectra on soft soil sites. The method takes into account modifications of the seismic waves by the soil layers, giving due considerations to factors such as the level of bedrock shaking, material non-linearity, seismic impedance contrast at the interface between soil and bedrock, and plasticity of the soil layers. The model is particularly suited to applications in regions with a paucity of recorded strong ground motion data, from which empirical models cannot be reliably developed