While the application of antenna diversity in a narrow band communication
system is well understood, little research has been done on antenna effects in wide-band
channels. Research has shown that circular polarization (CP) is more robust in combating
multipath than linear polarization in line-of-sight channels. One objective of this thesis is
to study the effects of antenna polarization and antenna pattern on multipath delay spread
and path loss in indoor obstructed (OBS) wireless channels. A wide-band experiment was
performed in a two-floored modern office building at 2.4SGHz in August 1991. Some
preliminary results are as follows. Circular polarization cannot reduce delay spread in
OBS channels and CP signals are more vulnerable to depolarization in OBS channels.
Our results show that vertically polarized (VP) directional antennas at both the transmitter
and the receiver can give better delay spread and path loss results than other antenna
combinations. The performance of VP directional antennas are found to be sensitive to
the alignment of the antennas, and the performance gain over omnidirectional antennas
degrades as shadowing effects increase.
In the second half of the thesis, a deterministic wide-band propagation model that
can predict channel impulse responses inside buildings is proposed and implemented. The
three dimensional image-based propagation model includes effects of antenna pattern,
antenna polarization, geometry of the building, and building materials. Comparisons
between measured and predicted power delay profiles are given in Chapter Seven.
Preliminary results show that the worst case path loss error is IOdB, and the standard
deviation of path loss error is 4.6dB. For most cases, predicted rms delay spread values
are 20ns within the measured values. Possible prediction errors are due to unmodeled
furniture inside the offices and limitations of Geometrical Optics (GO) assumptions. The
algorithm is shown to be more efficient than brute force ray tracing algorithm if the
number of objects are on the order of a few hundred. Acceleration techniques for the
algorithm are also discussed in the thesis.
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