In multilateral systems tags are usually simple devices acting only as the source of UWB signal. Therefore the position is derived in another more powerful unit (a system controller). Such approach raises some problems when the number of system tags is large but thanks to the tag’s simplicity and its low energy requirements it is a good choice for long-term location tracking systems. The exemplary multilateral UWB localization system architecture is shown in Fig. 1
Fig. 1 Multilateral positioning system architecture (developed within the NITICS project)
The system infrastructure consists of anchors measuring time of arrival of signals sent by the tag. Measurement results are sent to the system controller over WiFi link, where they are processed (TDOAs are calculated) and tag localization is calculated. Such architecture was used in a system developed within the NITICS project. In that system, anchor node synchronization was achieved by introducing additional reference node.
The multilateral system developed by the UWB Systems Group uses DWM1000 UWB radio modules both in system tags and anchors. The block diagram of the used tag is shown in Fig 2.
Fig. 2 Tag’s block diagram
The tag device is battery-supplied. To reduce power consumption, the tag operation is controlled by low power FRAM microcontroller. The tag includes also accelerometer and environmental sensors which can be used to improve positioning system accuracy. The tag PCB and assembled device are presented in Fig. 3
Fig. 3 Tag’s PCB and the prototype tag in the enclosure (55x70x15 mm)
The anchor node architecture is shown in Fig. 4.
Fig. 4 Anchor node block diagram
The WiFi module used in the anchor allows to transmit measurement results to the positioning server. Atmospheric pressure meter can be used as an altitude reference for the environmental sensor embedded in the tag.
Fig. 5 Anchor node PCB and the prototype node in the enclosure