Interferences and Shadowing in Multi-Lane UHF RFID-Based Vehicle Identification Systems

Interferences, like reader-to-tag interferences, and shadowing can lower the performance of ultra high frequency (UHF) radio frequency identification (RFID) vehicle identification systems on highways. Thus, it is important to know how much influence these effects have on the reliability of such systems, which is the main goal of this work. To get an appropriate model for the reader-to-tag interferences, measurements of the number of reads per minute in a two-reader environment are shown. It turns out that at a signal to interference ratio (SIR) of more than 6 dB the desired reader dominates the communication over the interfering reader. With this model, the impact of the reader-to-tag interferences is analyzed by simulating two scenarios; a car driving along the center of a lane and driving between two lanes. It turns out that the number of reads is reduced by $\approx$ 63.2% if the car drives between two lanes but that the absolute number of 25 is still enough to allow a robust identification. A third scenario, where a truck is driving in front of a car, shows that shadowing is negligible regarding the number of reads, even for relatively small distances between the vehicles.