Poster: Accurate Cross-Technology Clock Synchronization Among Off-the-Shelf Wireless Devices

Clock synchronization in distributed IoT systems is a necessary feature to allow a coherent data collection and event detection. This task is challenging as today's IoT systems often consist of heterogeneous wireless devices using incompatible technologies. Because of this, existing solutions often resort to the use of multi-radio gateways, which allow an indirect synchronization, but increase end-to-end delays. In this work, we present X-Sync, a novel approach allowing a direct, bidirectional clock synchronization across wireless devices with incompatible physical layer. X-Sync leverages cross-technology communication in combination with MAC timestamping and performs a repetitive sampling of the received signal strength to accurately determine the beginning of a cross-technology frame. Preliminary results on off-theshelf devices show that X-Sync can reach an accuracy < 1μs.