# Locating Infectious Sources Using Bluetooth System of Smart Devices  
[PERSON]  
1 College of Information Science and Technology, Beijing University of Chemical Technology,  
Beijing 100029, China; [EMAIL_ADDRESS]  
[PERSON]  
2 Beijing Aerospace System Engineering Research Institute, Beijing 100076, China; [EMAIL_ADDRESS]  
[PERSON]  
1 College of Information Science and Technology, Beijing University of Chemical Technology,  
Beijing 100029, China; [EMAIL_ADDRESS]  
Footnote 20: email: {[PERSON], 202 technologies such as Bluetooth, Global Positioning System (GPS), Global System for Mobile Communication (GSM) technology, mobile tracking technology, and card transaction data. For instance, Health Code (China) and Corona100m (Korea) are applications that identify and store users' location through GPS or GSM tracking. The government usually collects location data centrally, and contact tracking programs are mandatory in both countries. The Health Code's holder's movement is restricted by its color [14; 15], which achieves isolation to some extent. However, it cannot be communicated between different provinces. In addition to GPS positioning, many contact tracking applications use Bluetooth to estimate the distance between smartphones to protect privacy, such as COVIDSafe in Australia and TraceTogether in Singapore [16]. Australia's COVIDSafe uses Bluetooth to record the information of people who stayed for a set time within a set distance, and it will be automatically cleared after 21 days [17]. This reduces the time needed to find and locate close contacts to a certain extent. However, there are strict restrictions on the duration of stay. Furthermore, Apple and Google jointly developed an API for exposure notification, which can be used across borders. It is mainly based on the DP3T protocol [18], a decentralized protocol. Exposure notification APIs have been applied by applications in many countries, such as COVID Tracker in Ireland and My Trace in Malaysia [19]. The use and implementation largely depend on the corresponding public health department, and the authorities need to follow development standards such as privacy and security. In addition to national application development, many research institutions and scholars have carried out a lot of related research. Nowadays, there are several types of related research on the use of Bluetooth for digital tracking. Firstly, many studies have used RSSI-based distance estimation. The authors of [20] improved the accuracy of distance estimation based on RSSI, while the authors of [21] found a method to maintain social distancing by RSSI. Secondly, some studies have optimized the framework design for privacy security. The authors of [22] outline three common tracking application architectures and discuss privacy security issues. The authors of [23] developed a privacy-preserving mobile and fog computing framework to track infections and suspected cases through fog nodes without revealing the identity of the infected person. Thirdly, some studies have assessed the risk level. The authors of [24] use a combination of Bluetooth and GPS, providing a self-assessment of the severity of the new coronavirus. The authors of [25] use different features to calculate the matching scores of two users to complete contact tracking. However, the above level assessment method given in those papers does not have real-time dynamics. Therefore, the problem is that existing technology cannot accurately locate the sources of infection, and the epidemic prevention and control measures are inadequate. Taking all of this into account, this paper presents a system and method which can effectively locate the sources of infection with Bluetooth to solve the predicament. The system needs a Bluetooth system of smartphones and a server. We have designed and applied for a patent for the design of this system [26]. This system provides the precise location of the infection sources based on GPS and Bluetooth, enabling real-time recording and close contact tracking.