Localization via Radio Frequency Identification (RFID) is frequently used in
different applications nowadays. It has the advantage that next to its
ostensible purpose of identifying objects via their unique IDs it can
simultaneously be used for the localization of these objects. In this work it
is shown how Received Signal Strength Indicator (RSSI) measurements at
different antennae of a passive UHF RFID label can be combined for
localization. The localization is only done based on the RSSI measurements
and a Kalman Filter (KF). Because of non-linearities in the measurement
function it is necessary to incorporate an Extended Kalman Filter (EKF) or an
Unscented Kalman Filter (UKF) where simulations have shown that the UKF
performs better than the EKF. Additionally to the selection of the filter
there are different possibilities to increase the localization accuracy of
the UKF: The advantages of using Reference Tags (RT) or more than one tag per
trolley (relative positioning) in combination with an Unscented Kalman Filter
are discussed and simulations results show that the localization error can be
decreased significantly via these methods. Another possibility to increase
the localization accuracy and in addition to achieve a more realistic
simulation is the consideration of the angle between reader antenna and tag.
Simulation results with the incorporation of different numbers of fixed
antennae lead to the conclusion that this is a useful surplus in the
localization