A parking spot occupancy sensor based on commodity wireless chipsets

An important prerequisite for smart parking management systems are accurate and reliable occupancy sensors for individual parking spots. Since those systems are often equipped with a wireless interface for data exchange, it is reasonable to re-use the involved wireless chipsets for sensing purposes. In this contribution, a parking spot sensor approach is discussed that solely features low-cost wireless communication devices. For this, a 2.45 GHz transmitter receiver pair is installed on the floor in the center of a parking spot. It is shown that the frequency derivative, i. e. the channel dependency, of the Received Signal Strength strongly correlates with the presence of a car on a parking spot. Based on this observation, a linear classifier approach is suggested to predict the state of an observed parking spot. An experimental evaluation of the proposed sensing approach was carried out in both a parking garage and on an open-air parking place. The achieved occupancy detection accuracy of up to 99.0 % is competitive with existing, e. g. radar based, sensing approaches, while featuring a significant cost reduction at the same time.