Local Clock Synchronization Research Articles

First experimental results of the cosmic time synchronizer for a wireless, precise, and perpetual time synchronization system

In 2022, the idea of the cosmic time synchronizer (CTS) was proposed for a precise wireless synchronization of local clocks (<100ns). Because CTS does not require critical timing information traffic among CTS sensors, the technique can be considered robust against jamming and spoofing. In this work, a small-scale CTS sensor network has been developed and tested for the first time. Good time synchronization performances were obtained for a short-haul configuration (30-35ns (SD, 1 σ), over 50-60m). Based on the results of this work, CTS could be potentially conceived as a 'self-adjusting' system, offering high level continuous (perpetual) performances, to be considered either as a backup chain for GPS disciplined oscillators (GPS DO), a standalone standard for frequency and time interval measurements, or as a tool for the dissemination of reference time scales to final users, with improved characteristics in terms of robustness and reliability.

E-SATS: An Efficient and Simple Time Synchronization Protocol for Cluster- Based Wireless Sensor Networks

Over the past decade, the Internet of Things (IoT) has attracted enormous interest from the research community and industry. IoT requires a synergy of various technologies, and wireless sensor networks (WSNs) are poised to play a critical role in many IoT applications like weather monitoring, smart-grids, smart-city and so on. The synchronization of local clocks of the WSN nodes is essential in many network functionalities, and thus a time synchronization protocol is required in WSNs. Although several synchronization protocols have been proposed for WSNs, most of them are simulation-based works. They make many assumptions at a high-abstraction level and do not consider the conditions of the line-of-sight (LOS) in the network. These factors significantly affect the performance of these protocols. Thus, conclusive experimental proof of the effectiveness of these protocols for different LOS conditions is required. In this direction, this paper proposes a time synchronization protocol called efficient and simple algorithm for time synchronization (E-SATS) for a cluster-based WSN. In this paper, E-SATS has been tested on a large-sized WSN testbed in different LOS scenarios and compared with the existing state-of-the-art protocols. E-SATS outperformed existing protocols by achieving up to six times better accuracy as compared to existing protocols with significantly lesser computations and energy consumption.

On limit laws of multi-dimensional stochastic synchronization models

Lévy stochastic processes and related fine analytic properties of probability distributions such as infinite divisibility play an important role in construction of stochastic models of various distributed networks (e.g., local clock synchronization), of some physical systems (e.g., anomalous diffusions, quantum probability models), of finance etc. Nevertheless, little is known about limit probability laws resulted from the long time behavior of such stochastic systems. In this paper we will focus on the impact of interaction graph topologies on limit laws of multicomponent synchronization models.

PRECISE SYNCHRONISATION IN INDUSTRIAL SYSTEM USING IEEE 1588 PRECISE TIME PROTOCOL

Nowadays there is a frequent demand to increase the quality of synchronization in industrial distributed systems. Node synchronization can be implemented in the Ethernet network using time protocols, e.g. IEEE 1588 Precise Time Protocol (PTP). However, active network components like switches and routers have negative influence on achieved accuracy of synchronization because they affect a packet delay variation in the network. To suppress this effect, special (but expensive) industrial switches, with a packet propagation delay correction, can be used. Another way using either low cost GPS receivers for synchronization of local clocks or a special timing for data transfer is described in the paper. It will allow a cheaper solution that preserves high quality of synchronization. Besides, a device for packet delay measurement (PTP tester) was designed and developed to be possible to evaluate the proposed methods.

Dynamic FTSS in asynchronous systems: The case of unison

Distributed fault-tolerance can mask the effect of a limited number of permanent faults, while self-stabilization provides forward recovery after an arbitrary number of transient faults hit the system. FTSS (Fault-Tolerant Self-Stabilizing) protocols combine the best of both worlds since they tolerate simultaneously transient and (permanent) crash faults. To date, deterministic FTSS solutions either consider static ( i.e. fixed point) tasks, or assume synchronous scheduling of the system components. In this paper, we present the first study of deterministic FTSS solutions for dynamic tasks in asynchronous systems, considering the unison problem as a benchmark. Unison can be seen as a local clock synchronization problem as neighbors must maintain digital clocks at most one time unit away from each other, and increment their own clock value infinitely often. We present several impossibility results for this difficult problem and propose an FTSS solution (when the problem is solvable) for the state model that exhibits optimal fault-containment.

Optimal Synchronization of Local Clocks by GPS 1PPS Signals Using Predictive FIR Filters

In this paper, we discuss optimal synchronization of local clocks using Global Positioning System (GPS) one-pulse-per-second (1PPS) timing signals. To eliminate sawtooth errors that are peculiar to the 1PPS signals and optimally steer the clock errors each M seconds, we propose the use of a ramp-predictive finite-impulse-response (FIR) filter that is known to be optimal for clock models on large averaging horizons. A low-pass filter is used to smooth the hold filter output between the optimally predicted points. A GPS-locked crystal clock has been investigated in detail in terms of the time interval error, Allan deviation, and precision time protocol (PTP) variance. A high-efficiency implementation of the proposed synchronization algorithm is experimentally demonstrated.

Systematic design of a family of attack-resistant authentication protocols

Most existing designs for two-way cryptographic authentication protocols suffer from one or more limitations. Among other things, they require synchronization of local clocks, they are subject to export restrictions because of the way they use cryptographic functions, and they are not amenable to use in lower layers of network protocols because of the size and complexity of messages they use. Designing suitable cryptographic protocols that cater to large and dynamic network communities but do not suffer from these problems presents substantial problems. It is shown how a few simple protocols, including one proposed by ISO, can easily be broken, and properties that authentication protocols should exhibit are derived. A methodology for systematically building and testing the security of a family of cryptographic two-way authentication protocols that are as simple as possible yet resistant to a wide class of attacks, efficient, easy to implement and use, and amenable to many different networking environments is described. Examples of protocols of that family that presents various advantages in specific distributed system scenarios are discussed. >