CheepSync
Sabarish Sridhar, Prasant Misra, Jay Warrior · 2015
Clock synchronization is highly desirable in distributed systems, including many applications in the Internet of Things and Humans (IoTH). For IoTH, Bluetooth Low Energy (BLE) - a subset of the recent Bluetooth v4:0 stack - provides a low-power and loosely coupled mechanism for sensor data collection with ubiquitous units (e.g., smartphones and tablets) carried by humans. This fundamental design paradigm of BLE is enabled by a range of broadcast advertising modes. While its operational benefits are numerous, the lack of a common time reference in the broadcast mode of BLE has been a fundamental limitation. This work presents and describes CheepSync: a time synchronization service architecture for BLE advertisers. We implement CheepSync on custom designed nRF24Cheep beacon platforms (as broadcasters) and commercial off-the-shelf Android ported smartphones (as passive listeners); and show that the average (single hop) time synchronization accuracy is in the 10 μs range.