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Development of a low cost RF based indoor tracking system

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Local positioning, also known as indoor localization is a well known problem that has been in the spotlights for the past years. Once the location of an object or person is known there are many interesting applications.

One can use this information to give directions to tourists in an exhibition as well as giving nurses directions to a patient that needs their attention. The same system can be used to keep track of products in a warehouse.

Many of the current commercial solutions to this depend on the 2.4 GHz network. While these systems have a good accuracy they tend to lead to complex and expensive solutions that are highly sensitive to signal reflections and interference.

To avoid these problems, a low frequency based positioning system (433.9 MHz) has been developed from scratch: the mobile objects emit a signal which is received by the Rx-Nodes. The Rx-Nodes transmit the captured signal together with the Received Signal Strength Indicator (RSSI) over a CAN bus towards the gateway. The gateway transfers the obtained data over an Ethernet connection to a centralized server, where the positions of the different tags are evaluated upon the positions of all Rx-Nodes and the received RSSI values.