THESIS
2020
xiii, 70 pages : illustrations ; 30 cm
Abstract
Location Based Services (LBSs) have led to an increase in demand for Device-Free
Localization (DFL) in the indoor environment. Radio Tomographic Imaging (RTI) is one well-known
localization algorithm that can estimate the position of a physical object on the basis of
the received signal strength indicator (RSSI) changes in the environment that are acquired by
Wi-Fi or Wireless Sensor Networks (WSNs). This thesis makes two significant contributions.
The first contribution involves the demonstration of the RTI approach by utilizing full
electromagnetic simulations of an indoor environment. In particular, we considered dielectric
cylinders with varying permittivities but fixed radius in which 20 Wi-Fi nodes are deployed on
the perimeter (3 m by 3 m) of a region to perform RTI. The...[
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Location Based Services (LBSs) have led to an increase in demand for Device-Free
Localization (DFL) in the indoor environment. Radio Tomographic Imaging (RTI) is one well-known
localization algorithm that can estimate the position of a physical object on the basis of
the received signal strength indicator (RSSI) changes in the environment that are acquired by
Wi-Fi or Wireless Sensor Networks (WSNs). This thesis makes two significant contributions.
The first contribution involves the demonstration of the RTI approach by utilizing full
electromagnetic simulations of an indoor environment. In particular, we considered dielectric
cylinders with varying permittivities but fixed radius in which 20 Wi-Fi nodes are deployed on
the perimeter (3 m by 3 m) of a region to perform RTI. The RTI approach is based on the line-of-sight (LOS) weighting model with total variation-based regularization which is used to
reconstruct and localize the position of the cylinder at high resolution.
The second contribution of the thesis is to utilize the knowledge and fundamentals from the
simulations to develop an experimental setup by using inexpensive Wi-Fi hardware modules
with directional antenna. We performed experiments on the Wi-Fi hardware modules itself by
comparing the mean RSSI of two Wi-Fi hardware modules with the two-ray ground-reflection
model at incremental distances in order to explore the impact of multipath fading from the
ground and its reflection coefficient. We also introduced a physical object between two Wi-Fi
hardware modules to observe the interference caused on the Wi-Fi signal and changes in the
RSSI measurements. Finally, we developed a domain of interest identical to the simulations
and placed physical objects in the region at different coordinates in order to reconstruct its
image and localize its position.
Through both the simulations and experimentation, the RTI methodology is suitable for
reconstructing and localizing objects with high permittivity such as humans in the domain of
interest. However, RTI tends to face issues with reconstructing images and localizing physical
objects with lower permittivities thus motivating further future investigations.
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