This paper presents an early warning system based on IEEE 802.15.4 to reduce the risk of collisions between pedestrians and cars. Here, it is of great interest how far the car is situated from the person, but also from which direction the traffic participants approximate. Therefore, we evaluate the performance of two different directional antenna types for a robust, compact and low-cost direction-of-arrival estimation. The first analyzed antenna is a rotating directional Yagi PCB antenna, mounted on a stepper motor reflecting a reference antenna type due to its clearly defined radiation pattern, whereas the second one is a dielectric embedded ESPAR (DE-ESPAR) antenna array using reactively loaded parasitic elements. As interference and noise in the link measurements caused by multipath propagation effects can harm the achievable accuracy, we will demonstrate the feasibility of our approach by carrying out a highly detailed ray tracing analysis within challenging urban scenarios. Furthermore, we show that our approach is even suitable for scenarios in which a line of sight cannot always be guaranteed and in which the nodes do not lie within the same azimuth plane. Finally, we will conclude this work with experimental results.
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