  An increasingly important requirement for many novel applications is sensing
the positions of people, equipment, etc. GPS technology has proven itself as a
successfull technology for positioning in outdoor environments but indoor no
technology has yet gained a similar wide-scale adoption. A promising indoor
positioning technique is radio-based location fingerprinting, having the major
advantage of exploiting already existing radio infrastructures, like IEEE
802.11, which avoids extra deployment costs and effort. The research goal of
this thesis is to address the limitations of current indoor location
fingerprinting systems. In particular the aim is to advance location
fingerprinting techniques for the challenges of handling heterogeneous clients,
scalability to many clients, and interference between communication and
positioning. The wireless clients used for location fingerprinting are
heterogeneous even when only considering clients for the same technology.
Heterogeneity is a challenge for location fingerprinting because it severely
decreases the precision of location fingerprinting. To support many clients
location fingerprinting has to address how to scale estimate calculation,
measurement distribution, and distribution of position estimates. This is a
challenge because of the number of calculations involved and the frequency of
measurements and position updates. Positioning using location fingerprinting
requires the measurement of, for instance, signal strength for nearby base
stations. However, many wireless communication technologies block communication
while collecting such measurements. This interference is a challenge because it
is not desirable that positioning disables communication. An additional goal is
to improve the conceptual foundation of location fingerprinting. A better
foundation will aid researchers to better survey and design location
fingerprinting systems.
