Abstract
Indoor environments---characterised by obstacles such as walls, floors,
ceilings, and furniture---provide a number of challenges for location
sensing. In particular, these environments prohibit the use of common
outdoor systems such as GPS. Many inexpensive indoor positioning systems
use the properties of ultrasound to provide spatial information to their
algorithms. Traditionally, this information is in the form of range
measurements, obtained using a combination of ultrasonic signals and
electromagnetic signals. The main disadvantage to this dual-medium approach
is that it requires more hardware than an approach that only uses one
medium.
In this thesis, we demonstrate that it is possible to position mobile
computers in an indoor environment using only narrowband ultrasound. We
describe the design, implementation and evaluation of two novel systems: the
Synchronous Buzz and the Asynchronous Buzz positioning systems. In
both systems, the only form of measurement is from narrowband ultrasound
signals originating from beacons in the environment. Positioning is made
possible through the use of transmission patterns, which communicate timing
information from the infrastructure to receiving wearable devices. Compared
with traditional systems, our approach saves on component costs and power
consumption, while improving on form factor.
The evaluation of the systems is done through the use of a custom built
simulator and two real-world experiments. The simulator uses a constrained
random-walk to generate realistic paths of a wearable user. Sensor noise,
reflections, occlusions, as well as beacon locations can all be controlled
within the simulator's environment. The proposed real-world experiments
compare the paths generated by the positioning algorithms to two different
ground-truths: a known static path followed by the wearable and one captured
by a high-speed camera. Based on the results of the evaluations, we provide
recommendations for the uses of our systems.
Translated title of the contribution | The Buzz: Narrowband Ultrasonic Positioning for Wearable Computers |
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Original language | English |
Publication status | Published - 2007 |