  Ultra-wideband positioning systems intended for indoor applications often
work in non-line of sight conditions, which result in insufficient precision
and accuracy of derived localizations. One of the possible solutions is the
implementation of cooperative positioning techniques. The following paper
describes a cooperative ultra-wideband positioning system which calculates tag
position from TDOA and distance between tags measurements. In the paper
positioning system architecture is described and an exemplary transmission
scheme for cooperative systems is presented. Considered localization system
utilizes an Extended Kalman Filter based algorithm. The algorithm was
investigated with simulations and experiments. Conducted experiment consisted
in fusing results gathered from typical TDOA positioning system infrastructure
and ranging results obtained with ultra-wideband radio modules. The research
has shown that the use presented cooperative algorithm increases positioning
precision.
