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TU München team develops new technique for accurate distance measurement by advanced driver assistance systems using cooperative transponders

Basic concept for range detection using cooperative transponders. Click to enlarge.

As part of the “cooperative transponder” research project Ko-TAG (earlier post), researchers at the Technische Universität München (TUM) developed a new approach to distance measurement to enable advanced driver assistance systems (ADAS) in cars to pinpoint the location of pedestrians and cyclists even in non-line-of-sight situations—i.e., when they are hidden from the driver’s view.

In this scheme, pedestrian’s and cyclist’s cell phones serve as transponders. On-board positioning systems compute the projected trajectory of the transponders and initiate an emergency braking sequence in case a pedestrian or cyclist moves into the path of a car.

The measurement principle. Click to enlarge.

The technique developed by Professor Erwin Biebl and his team at TUM can now determine the distance to an object to an accuracy of a few centimeters within just a few microseconds (millionths of a second). The on-board positioning system achieves this by sending a unique series of codes to the transponder. The transponder, in turn, modifies the code sequence and returns it in a very precise temporal pattern.

Warning the driver or initiating an emergency braking sequence must generally happen before the pedestrian steps into the street. At the same time, the probability of false alarms must be kept extremely low if drivers are to deem the system effective and use it. Accurate prediction of movement is thus indispensable.

In the context of their research, the scientists were able to reduce the measurement errors to a few picoseconds (billionths of a second).

With this, we achieved an accuracy in distance measurement of a few centimeters. Together with the unique code-based process, this is the explanation for the exceptional performance and an important unique selling point of our system.

—Professor Biebl

The small transmitters can be integrated in clothing or school bags. However, cell phones could also serve as transponders in the future since the majority of people carry a cell phone with them most of the time anyway. Only minor hardware modifications would be required. One major cell phone manufacturer has already expressed interest in the system, according to the TUM team.

In addition to the Department of High Frequency Technology at the Technische Universität München, Fraunhofer IIS, BMW Forschung und Technik GmbH, Continental Safety Engineering International GmbH, Daimler AG, the Heinrich Hertz Institute of the Fraunhofer Gesellschaft, and the Steinbeis Innovation Center for Embedded Design and Networking collaborated on this project funded by the German Federal Ministry of Economics and Technology.




Pedestrians, do NOT forget to take out your cellphone, or you are hamburger!


"One major cell phone manufacturer has already expressed interest in the system, according to the TUM team. "

If the cell phone makers can do this, measuring the position of a cell phone to a few centimeters, then they could also disable the cell phone in a driver's hand.


Using an active (transponder) system instead of a passive (radar) system has many advantages and does not have to cost much more.

To be safe, the system needs to have both modes active at the same, though. One car can follow another closely (platoon) as long as it is receiving an active transponder signal. If the the receiver misses a detection, then it has to fall back to radar mode and increase the vehicle distance by easing up to account for the lesser accuracy and reliability of pure radar.


Beware of the possibility of jamming or spoofing any wireless system. Without some sort of coded security, as well as a directional transmitter and receiver, there could very well be simple methods for sabotage.

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