RFID BASED INDOOR LOCATION TRACKING
Radio Frequency Identication (RFID) attracts considerable attention because
of its low cost and various area of applications. Location estimations based on received
signal strength (RSS) in wireless technologies took the topic of localization using RFID
technology into agenda. In our study, changes in the RSS values according to distance
have been investigated in an indoor environment based on both passive and active tags.
For the system in which active RFID tags are used, localization has been made using
reference tags. An online radio map of the environment is created with the help of
deployed reference tags. A nearest neighbor algorithm is applied in order to localize
the tracked tag. However, unpredictable and non-uniform behavior of tags resulted in
inappropriate location estimations. Passive tags, on the other hand, severely suers
from shadowing eect, creating biases towards to shadowed tags. The tag worn by the
subject was undetectable because of the signal absorption by the human body. We
have developed an algorithm estimating the location based on the drops in RSS value
of the tags as tracked subject is passing by. We achieved a mean error of 0:25 m in a
2x2:5 m2 indoor environment.