Kavraki Lab

Physical and Biological Computing

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Keywords:

Abstract:

A key subproblem in the construction of location-aware
systems is the determination of the position of a mobile
device. This paper describes the design, implementation and analysis
of a system for determining position inside a building from measured
RF signal strengths of packets on an IEEE 802.11b wireless Ethernet
network. Previous approaches to location-awareness with RF signals
have been severely hampered by non-linearity, noise and complex
correlations due to multi-path effects, interference and
absorption. The design of our system begins with the observation
that determining position from complex, noisy and non-linear signals
is a well-studied problem in the field of robotics. Using only
off-the-shelf hardware, we achieve robust position estimation to
within a meter in our experimental context and after adequate
training of our system. We can also coarsely determine our
orientation and can track our position as we move. By applying
recent advances in probabilistic inference of position and sensor
fusion from noisy signals, we show that the RF emissions from base
stations as measured by off-the-shelf wireless Ethernet cards are
sufficiently rich in information to permit a mobile device to
reliably track its location.