An Improved Network Time Protocol for Industrial Internet of Things.

Area of Science:

• Industrial Internet of Things (IIoT)
• Network Time Protocol (NTP)
• Real-time Systems

Background:

• Accurate time synchronization is critical for industrial Internet of Things (IIoT) applications, enabling coordinated machine actions within 1 ms.
• Traditional Network Time Protocol (NTP) mechanisms fail due to time-varying network packet travel times, leading to synchronization errors.

Purpose of the Study:

• To propose a low-cost modification to the Network Time Protocol (NTP) for improved time synchronization accuracy in industrial environments.
• To ensure clock differences between NTP clients and servers remain within 1 ms in wired networks.

Main Methods:

• Implemented a modified NTP incorporating adaptive clock adjustment and clock skew compensation.
• Adaptive clock adjustment skips offset calculations when Round Trip Time (RTT) exceeds a defined threshold.
• Clock skew compensation addresses natural clock drift between devices.

Main Results:

• The proposed NTP modification effectively controls clock differences within 1 ms in a wired network.
• Optimal synchronization accuracy was achieved when the RTT threshold was set at 1.7 ms in the experimental environment.
• Both adaptive clock adjustment and clock skew compensation are noted as environment- and device-dependent.

Conclusions:

• The modified NTP offers a practical solution for achieving high-precision time synchronization in industrial IoT settings.
• The integration of adaptive clock adjustment and clock skew compensation significantly improves NTP's reliability despite network variability.
• The findings demonstrate the feasibility of sub-millisecond time synchronization crucial for time-critical industrial operations.