Where did I put ....?

The problem

In our house, objects such as books, keys, or toys frequently get lost. Perhaps we can "tag" them in some way, and track the tag? Of course, such a system has to be cheap, battery-less (for the tags), and sufficiently accurate for its purpose.

Tagging objects with GPS transponders is expensive and not battery-less. GPS is accurate, but only outdoor. Near-field communication (NFC) labels are cheap (< 1 euro) and battery-less. A problem is that their read-out range is small.

The read-out device can be inside a smartphone or an NFC-equipped smartwatch, or something else that is always on me. Then, the device can record and store the "last known location", before it lost contact. This assumes that the location of the read-out device itself is known. Then, if I don't remember the location of the object, I can use an app which will direct me to the recorded location.

NFC

Smartphones or watches equipped with NFC can be paired with NFC Tags or stickers which can be programmed by NFC apps to automate tasks. These programs can allow for a change of phone settings, a text to be created and sent, an app to be launched, or any number of commands to be executed, limited only by the NFC app and other apps on the smartphone. NFC stickers, key fobs, or cards do not require batteries. Theoretical working distance with compact standard antennas: up to 20 cm (practical working distance of about 4 cm).

GPS

A GPS accuracy 25 cm is known to be available. However, GPS is not available indoors. Also, its energy consumption is significant.

Assignment



• How to locate the read-out device indoors? Can we use GPS? We need a 3D location and sufficient accuracy. Can we use alternatives such as WLAN signals? 
• What is the required operational distance for a NFC label to work in this case? 
• What type of apps do we need and what is their functionality? 
• What is a suitable protocol to track many objects and still keep the battery consumption of the read-out device acceptable?

Contact

Last modified: 2023-01-13