P4: ULPT – Ultra-Low Power Transponders for vulnerable road-side users

Project leader: Marco Bekooij (UT/NXP)

Energy autonomous communication devices that will not only enhance our comfort but will also improve our safety, will soon emerge on the market. Examples of such devices are autonomous WLANs for vehicular networks (IEEE 802.11p): transponders that can be mounted on bicycles to inform car-drivers about the presence of vulnerable road-users such as children going to school by bike. Advanced versions of these transponders should not only indicate presence but should be able to broadcast the trajectory of the bike. Given the available energy budgets and the energy inefficiency of currently available technology, initial versions of these transponders will not be equipped with a GPS and therefore will need to communicate using e.g. Bluetooth with the bike’s computer or the user’s smartphone to estimate speed and position in order to warn the drivers and prevent collisions.

These transponders will only become successful in the market if they are easy to install on every bike without wiring and are maintenance free. This implies that these transponder should be able to scavenge sufficient energy from the environment and store it in a supercapacitor. Initial estimates indicate that it is feasible to scavenge sufficient energy for a basic version of a transponder by making use of a small magnet mounted on a spoke like the ones used for wireless speed measurement devices. This basic version will only be able to transmit a very short data package with a fixed content over around 20 meters distance at a rate of a few Hz. Power management should enable that even if a biker stops, for example for a traffic light, there is still sufficient energy available in the supercapacitor to continue a few minutes at potentially a reduced transmission rate. The development of more advanced versions of the transponder that are capable of position estimation and trajectory transmission will require a significant improvement of energy scavenging capabilities and a reduction in energy usage of the transponder device. Similar technological improvements are needed to enable the development of energy autonomous transponders for pedestrians.