Overview of Time Synchronization for IoT Deployments: Clock Discipline Algorithms and Protocols

Abstract

Internet of Things (IoT) is expected to change the everyday life of its users by enabling data exchanges among pervasive things through the Internet. Such a broad aim, however, puts prohibitive constraints on applications demanding time-synchronized operation for the chronological ordering of information or synchronous execution of some tasks, since in general the networks are formed by entities of widely varying resources. On one hand, the existing contemporary solutions for time synchronization, such as Network Time Protocol, do not easily tailor to resource-constrained devices, and on the other, the available solutions for constrained systems do not extend well to heterogeneous deployments. In this article, the time synchronization problems for IoT deployments for applications requiring a coherent notion of time are studied. Detailed derivations of the clock model and various clock relation models are provided. The clock synchronization methods are also presented for different models, and their expected performance are derived and illustrated. A survey of time synchronization protocols is provided to aid the IoT practitioners to select appropriate components for a deployment. The clock discipline algorithms are presented in a tutorial format, while the time synchronization methods are summarized as a survey. Therefore, this paper is a holistic overview of the available time synchronization methods for IoT deployments.

Engineering Emergence: A Survey on Control in the World of Complex Networks

“…Real-time operation of networks as the backbone of communication for control systems introduces performance requirements related to the time in which information is produced (by the control system components) and transmitted (by the network) and translates to time synchronization issues across the network [50], or more precisely, the phase and frequency synchronization of tick generators [40,51]. Recent surveys indicate an increasing interest toward wireless networks [52][53][54][55][56].…”

Intro-Stabilizing Byzantine Clock Synchronization in Heterogeneous IoT Networks

“…In considering the overall problem, firstly, as real-world IoT networks are often across the WAN, LAN, and PAN areas [15], the first-of-all question is how a dependable CS system can be deployed in such an all-scale network. From the traditional viewpoints [22,23,45], current assumptions about the openworld adversaries might be overoptimistic.…”

“…Thus, in the IoT networks, to validate the assumption that there are at most f Byzantine nodes in the system, we do not allow the core BFT-CS algorithms to run across the WAN area. Meanwhile, as the terminal devices (such as the sensors and actuators) deployed in the PAN area of the IoT systems [15] are often energy-constraint (like the passive RFID tags), they can hardly be utilized as synchronization servers physically. So, we only allow these low-power end devices to be passively synchronized, just like the thin clients and thick clients proposed in [49].…”

Correlating Time Series Signals and Event Logs in Embedded Systems

“…In the literature, various synchronisation algorithms have been proposed, especially for distributed and IoT systems. They are based on exchanging synchronisation messages [33] or on time compensation schemes [34]. Unfortunately, using these approaches in external device monitoring is not satisfactory due to limited capabilities of accurate data acquisition systems.…”