Driver Arrival Sensing for Smart Car using WiFi Fine Time Measurements

Driver arrival sensing which enables the car to detect an approaching driver has been playing an important role in the evolving smart car system. This paper presents a driver arrival sensing scheme based on the fine time measurement (FTM) released in the IEEE 802.11mc protocol. We observe that when the initiating station (ISTA, such as a mobile phone or WiFi client) keeps moving towards the response station (RSTA, usually a WiFi access-point (AP)), there exists a knee point of the WiFi-FTM range estimation after which the variation of the WiFi-FTM range estimations follows a stable trend regardless of the environment. Inspired by such an observation, we propose a joint knee point detection and driver arrival time estimation algorithm based on the trend of WiFi-FTM range estimations. Given the arrival time, the car (RSTA) can determine the right time to start the service requested by the driver. We implement the proposed method using commercial 802.11mc WiFi chipsets and conduct extensive experiments in different parking lots with different testers. The results show that the scheme can achieve ≥ 92.5% accuracy with ≤ 1s arrival time estimation error.