Maximum Likelihood Estimation of Clock Skew in IEEE 1588 with Fractional Gaussian Noise

Abstract

To support system-wide synchronization accuracy and precision in the sub-microsecond range without using GPS technique, the precise time protocol (PTP) standard IEEE-1588 v2 is chosen. Recently, a new clock skew estimation technique was proposed for the slave based on a dual slave clock method that assumes that the packet delay variation (PDV) in the Ethernet network is a constant delay. However, papers dealing with the Ethernet network have shown that this PDV is a long range dependency (LRD) process which may be modeled as a fractional Gaussian noise (fGn) with Hurst exponent (H) in the range of0.5<H<1. In this paper, we propose a new clock skew estimator based on the maximum likelihood (ML) technique and derive an approximated expression for the Cramer-Rao lower bound (CRLB) both valid for the case where the PDV is modeled as fGn (0.5<H<1). Simulation results indicate that our new clock skew method outperforms the dual slave clock approach and that the simulated mean square error (MSE) obtained by our new proposed clock skew estimator approaches asymptotically the developed CRLB.

A Novel Clock Skew Estimator and Its Performance for the IEEE 1588v2 (PTP) Case in Fractional Gaussian Noise/Generalized Fractional Gaussian Noise Environment

“…This process has to achieve frequency (clock skew) and time (offset or phase) synchronization to ensure that all the components function accurately. There are three significant protocols for time and frequency distribution over the Network: global positioning system (GPS), network time protocol (NTP), and Precision Time Protocol (PTP) Pinchas [1]; Levy and Pinchas [2]; Karthik and Blum [3]. GPS offers frequency and time synchronization accuracy in the submicrosecond range Levy and Pinchas [2].…”

“…There are three significant protocols for time and frequency distribution over the Network: global positioning system (GPS), network time protocol (NTP), and Precision Time Protocol (PTP) Pinchas [1]; Levy and Pinchas [2]; Karthik and Blum [3]. GPS offers frequency and time synchronization accuracy in the submicrosecond range Levy and Pinchas [2]. However, it requires expensive equipment and routine maintenance Guruswamy et al [4].…”

“…According to Vyas et al [6]; Peng et al [7] the GPS also suffers from a weak indoor GPS signal. The NTP is not designed for local area networks (LANs) and has slow response and software clock implementations Levy and Pinchas [2]. Therefore, it can not achieve accurate results compared to the PTP protocol Pinchas [1].…”

“…It distributes a reference timing signal, where this signal can be extracted, processed, and frequency can be recovered from this signal by the Ethernet equipment clock (EEC) ITU-T Recommendation [10,11]. It should be pointed out that according to Levy and Pinchas [2], the EEC is not available in every system. Generally, the GPS or the SyncE are applied for frequency synchronization, where the PTP protocol and the GPS can be also applied for time or frequency synchronization as well unlike SyncE.…”

Moderate Deviations for Stochastic Fractional Heat Equation Driven by Fractional Noise

“…There are also many works about MDP about stochastic (partial) differential equations; some surveys and literatures could be found in Budhiraja et al [11], Wang and Zhang [12], Li et al [13], Yang and Jiang [14], and the references therein. On the other hand, fractional equations have attracted many physicists and mathematicians due to various applications in risk management, image analysis, and statistical mechanics (see Droniou and Imbert [15], Bakhoum and Toma [16], Levy and Pinchas [17], Mardani et al [18], Niculescu et al [19], Paun [20], and Pinchas [21] for a survey of applications). Stochastic partial differential equations involving a fractional Laplacian operator have been studied by many authors; see Mueller [22], Wu [23], Liu et al [24], Wu [25], and the references therein.…”