Prioritized Clock Synchronization for Event Critical Applications in Wireless IoT Networks

With the proliferation of the Internet of Thing (IoT) technologies in vertical industry applications, provisioning of accurate synchronization and low latency communication has become critical for dense wireless IoT networks to support distributed sensing and control. Due to the contention-based channel access, achieving accurate synchronization in most of unlicensed wireless IoT networks could be extremely challenging. Specifically, the critical challenge at medium access control (MAC) layer for dense IoT communication is how to eliminate random access delay while supporting a large number of heterogeneous nodes with diverse quality of service (QoS) requirements. In this paper, we propose an efficient MAC protocol for supporting distributed synchronization through guaranteed channel access for time-critical sensor nodes in dense wireless IoT networks. The proposed protocol assigns time slots to timestamp packets of the time-critical nodes using a prioritized channel access mechanism, and also guarantees channel access in event-based situations. In addition, the proposed protocol also provides deterministic scheduling for the scenarios where the delay bound of a certain priority traffic changes based on the circumstances of the emergency situation. Our results show that the proposed scheme significantly improves the synchronization precision of the event critical sensor nodes, and also enhances the reliability of overall IoT networks.