An RFID Based Smartphone Proximity Absence Alert System

We present the design, implementation, and evaluation of an RFID-based cellphone anti-lost and anti-theft measure. The cellphone owner is given an audio-visual alert at the very instant of the lost event, and the cellphone deduces the fact that it is away from its owner and executes the safety measures. This is realized by equipping the cellphone with a low-power RFID Reader and tagging the owner with a passive RFID token to determine a private space around him, which spans within 2-10 feet. We prototype an RFID Reader from discrete components under $60 which can transmit 30 dBm with -78 dBm sensitivity, and can also serve as an educational tool for academic learning. Our system works on automatic, timed, or accelerometer based thresholds. We interface our system with Samsung Galaxy Note2 and develop an Android User Interface. We carry out extensive indoor and outdoor experiments under static and dynamic scenarios to ascertain the Frontal and Angular ranges, energy and power consumption, and memory and computational overheads. Our salient contribution is a twofold probing scheme-a duty cycle approach that economizes battery overhead, mitigates false alarms and scans the tag for multiple times by leveraging the interrogation time and power. We argue that though our design is costly in power budget, it is highly economical on battery energy because of short interrogation cycles. We show that for 17 tag interrogations from 20-24 dBm, our scheme consumes 72.1 to 52.4 percent lower energy than a single Bluetooth device scan. For a fully embedded design, we propose System-on-Chip RFID solutions. We foresee our endeavor as a viable proximity absence detection scheme for short range applications and scenarios.