Distributed Synchronization for Massive IoT Deployments

摘要

Internet of things (IoT) is the paradigm to interconnect a large number of heterogeneous devices (sensors, smart phones, actuators, etc.), offering a solution for a massive connected network characterized by low-power and low data-rate. In communication architecture with heterogeneous requirements, there are challenges to be traded for such as connectivity, communication protocol, energy efficiency, proper modulation and coding. Timing and carrier frequency synchronization is a critical aspect to be considered in massive IoT development. In this paper, we propose a novel solution based on distributed synchronization that enables the connectivity of massive devices without any external reference timing agent. A common beacon with the same chirp-like signature is broadcasted by every device and the superimposition (collision) with the others represents a compound signature that embeds the reference of the network for synchronization, making thus the algorithm less complex. Beacon's collision is exploited here to drive the IoT network to global time and carrier frequency synchronization. Namely, each node estimates and compensates locally its synchronization state with respect to the ensemble signal from colliding beacons used as synchronization reference. Numerical analysis evaluates the proposed distributed synchronization performance for OFDM system as relevant for practical IoT settings in perspective of 5G systems.