Cooperative Multi-User Detection and Localization for Pedestrian Protection

In the proposed cooperative sensor system pedestrians carry a reactive transceiver which is interrogated by a localization and tracking unit in the car. The prototype system applies round-trip time-of-flight (RTOF) techniques for the determination of the distance between the transponder and the demonstrator vehicle. A smart antenna array integrated into the car is used to determine the direction-of-arrival (DoA) of the transponder´s response signal. Knowing the distance and azimuth angle relative to the car, the pedestrian´s position and movement are calculated. These data are used as input for a highly reliable collision warning and collision mitigation system. The sensor system is capable of addressing a huge number of communication partners within each measurement cycle. Additionally secure burst identification is ensured for a robust localization and the suppression of unwanted co-channel interference. This is achieved by using pseudo random coded signals with a time division multiple access (TDMA) method. The distance accuracy was improved by introducing a new mirror technique in combination with an interpolation algorithm. The prototype localization system set up at 2.4GHz covers a range up to 200m in free field condition. With the current system a distance resolution down to cm and an angular measurement accuracy of about 1 degree have been achieved.