Presence Detection Based on Bluetooth Low Energy Using the Exposure Notification Service

Detecting if a person is present offers a variety of use cases in a smart home environment. These start at energy saving methods, such as reducing the room temperature when no one is at home, and go as far as automated routines to turn off unnecessary lighting. In this paper, we propose a method to detect a user's presence based on the Bluetooth Low Energy Advertising of his mobile device. This method is based on an analysis of the Bluetooth behavior of common smartphones, which identifies the Exposure Notification Service (ENS) to provide a proper source of Bluetooth Advertising messages. The ENS was introduced in April 2020 to solve the too-long-too-close-problem in the fight against the COVID-19 pandemic. Given that the ENS provides periodic advertising by the mobile device, the user does not need to take any action to be identified by a presence detection system. Using a random resolvable Bluetooth address, this method can detect a user by identifying the used identity resolving key. This paper proposes a procedure to implement this method in low power smart home devices, ensuring that the impact on the devices' resources is as small as possible. The proposed method provided an automatic, reliable, scalable and low-cost way of detecting the user's presence. In addition it can count and identify the present users to enable new use cases.