ZigBee network positioning with support of Real-Time Kinematic GPS and terrestrial measurements

Ad hoc network based positioning is particularly useful when fixed positioning infrastructures are unavailable, or were destroyed in a disaster. It can also be used as an augmented system to continuously provide spatial information when satellite positioning systems fail. ZigBee is an emerging wireless technology based on the IEEE 802?15?4 standard. Its advantages include low cost, low power consumption and license free operating frequencies. In addition to applications for low volume data transmissions, some ZigBee modules such as the TI/Chipcon CC2431 already have a built-in location engine for positioning applications. One of the main challenges in ZigBee positioning is to obtain the coordinates of the ZigBee reference nodes that form a network of control points for position fixing. This is particularly challenging when the network is continuously expanding and covers areas with various obstructions, and when the control point coordinates of newly covered areas need to be defined in the ZigBee system. In this paper, the ZigBee wireless technology and its positioning concept is introduced, followed by an accuracy test along a long and narrow corridor and of a proposal of an algorithm for a quick establishment of a ZigBee network. Our indoor investigations show that the ZigBee positioning can generally achieve a better than 5 m accuracy, that a ZigBee network can be efficiently and effectively established with the support of Networked Transport of RTCM via Internet Protocol based Real- Time Kinematic GPS (NTRIP RTK GPS) and conventional measurements and that the network node connectivity status can be monitored by a modelling algorithm of the node connectivity matrix.