Extended Synchronization Protocol Based on IEEE802.1AS for Improved Precision in Dynamic and Asymmetric TSN Hybrid Networks

This paper proposes an extension of the precision time protocol (IEEE 802.1AS) to improve clock synchronization in hybrid networks including both wireless and wire-bound segments. This extension targets systems based on Time Sensitive Networking (TSN) such as industrial applications and vehicular systems. By considering the deterministic delays and the clock drift, the precision of the clock synchronization of the standard 802.1AS scheme can be significantly improved. Furthermore, in order to support dynamic communication environments with mobile nodes, the problem of asymmetric delays in the transmission of the timing packets of the synchronization protocol is also considered. Therefore, a Path Deviation Delay (PDD) filter is introduced to monitor the traffic behavior of timing packets as well as to exclude outlier values which can occur as a result of dynamic and asymmetric scenarios. The paper presents a simulation framework for the proposed protocol to evaluate it with TSN-based systems that support the TSN features (e.g. IEEE 802.1Qci and IEEE 802.1Qbv sub-standards). The simulation results show that the proposed protocol improves the synchronization precision compared with the standard 802.1AS protocol. It shows that the proposed protocol enhances the synchronization precision to less than 1 microsecond. In contrast, the synchronization error increases significantly with the standard protocol in the presence of different asymmetric ratios and in mobile node scenarios.