Time Synchronization in Short Range Wireless Networks

Abstract: Energy efficient wireless devices is a trend that has been on the rise the last few years. Energy efficiency properties may fill a function in wireless sensor networks where the devices could run on coin-cell batteries and still last for years. To make sense of the sensor data collected, there is a requirement of accurate time synchronization in the network. This report focuses on investigating if present time synchronization standards, NTP and PTP, and de facto-standards, RBS, TPSN, and FTSP, can provide sufficient accuracy in a network consisting of devices where energy efficiency and mobility are the ground pillars, or if accurate time synchronization and the constraints of highly energy efficient devices proves contradictory. The knowledge gained from studying the standards lay the foundation of a case study where RBS was implemented in a network consisting of Bluetooth low energy devices, proving that low millisecond accurate time synchronization was achievable using application based timestamping. Compared to wireless sensor networks consisting of devices not developed with today's high energy efficiency focus, the accuracy is a factor thousand less precise, but with some hardware features, like hardware based timestamping and a more accurate clock, it would not be impossible to reduce the gap.