# An Interactive Real-Time Locating System Based on Bluetooth Low-Energy Beacon Network +
###### Abstract  
The ubiquity of Bluetooth-enabled smartphones and peripherals has brought tremendous convenience to our daily life. In recent years, Bluetooth beacons have also been gaining popularity in implementing a variety of innovative location-based services such as self-guided systems in exhibition centers. However, the broadcast-based beacon technology can only provide unidirectional communication. In case smartphone users would like to respond to the beacon messages, they have to rely on their own mobile Internet connections to send the information back to the backend system. Nevertheless, mobile Internet services may not be always available or too costly. In this work, we develop a real-time locating system based only on the Bluetooth low energy (BLE) technology to support interactive communications by combining the broadcast and mesh topology options to extend the applicability of beacon solutions. Specifically, we turn the smartphone into a beacon device and augment the beacon devices with the capability of forming a mesh network. The implementation result shows that our beacon devices can detect the presence of specific users at specific locations, and then the presence state can be sent to the application server via the relay of beacon devices. Moreover, the application server can send personalized location-based messages to the users, again via the relay of beacon devices. With the capability of relaying messages between the beacon devices, it would be convenient for developers to implement a variety of interactive applications such as tracking VIP customers at the airport, or tracking an elder with Alzheimer's disease in the neighborhood. B 2018 18 1637 2018 21 May 2018 21 May 2  
objective--making the power consumption of wireless communication as low as possible in order to extend the lifetime of battery-operated IoT devices. Among these protocols, we see the advantage of BLE based on the fact that it is universally supported by almost every smartphone. That means if IoT devices communicate with each other using BLE, people can also communicate with these IoT devices intuitively through their smartphones. By contrast, if IoT devices run ZigBee, smartphones are unable to communicate with them directly because smartphones are without built-in ZigBee wireless interfaces. Solutions to this problem include augmenting the smartphone with a ZigBee USB dongle (e.g., [6]), or using a gateway device to bridge the ZigBee network and the Wi-Fi network (e.g., [7]) or the BLE network (e.g., [8]). Therefore, in this research we focus on naturally integrating BLE-enabled smartphones into the ecosystem of the BLE-based IoT environment by designing an interactive real-time locating system. BLE was first introduced to the Bluetooth specification in version 4.0 in 2010. It has become the most popular technology for low-power and short-range wireless communication in the application domain of consumer electronics. Compared with the classic Bluetooth (also known as Bluetooth Basic Rate/Enhanced Data Rate, or BR/EDR) which achieves high-speed transmission, BLE technology focuses on greatly reducing the power consumption and provides extremely low transaction latency with only a few milliseconds [9]. BLE-based IoT devices can be powered by coin cell batteries and run for several years on a moderate duty cycle without replacing the battery. Some studies compared the power consumption of BLE and ZigBee and found that BLE is more power-efficient than ZigBee [10; 11]. Based on the BLE technology, in 2013 Apple Inc. announced the iBeacon protocol [12] for the purpose of building location-aware applications. Specifically, an iBeacon message is a BLE advertising packet that contains a 16-byte universally unique identifier (UUID) and two 2-byte Major and Minor values. On receiving an iBeacon message, the receiver then uses these values to identify the iBeacon device which broadcasts the iBeacon message.