Time synchronization for deterministic communication
Mahin K. Atiq, Raheeb Muzaffar
TL;DR
The paper addresses the need for deterministic communication across multiple industries by focusing on time synchronization accuracy and low jitter in information delivery. It surveys time-synchronization mechanisms in wired and wireless integrated systems, emphasizing IEEE 802.1AS/gPTP, BMCA-based GM selection, redundancy with multiple GM domains, and the hot standby amendment. A key emphasis is on residence time, defined as the elapsed time between ingress and egress timestamping, which underpins accurate synchronization, and on 5G-TSN integration where 5G components timestamp gPTP messages and GNSS serves as an external clock. The work highlights practical implications for deploying deterministic networks in industrial and critical sectors and points to future work on tighter 5G/6G hot-standby integration to prevent timing gaps during clock failures.
Abstract
Deterministic communication is required for applications of several industry verticals including manufacturing, automotive, financial, and health care, etc. These applications rely on reliable and time-synchronized delivery of information among the communicating devices. Therefore, large delay variations in packet delivery or inaccuracies in time synchronization cannot be tolerated. In particular, the industrial revolution on digitization, connectivity of digital and physical systems, and flexible production design require deterministic and time-synchronized communication. A network supporting deterministic communication guarantees data delivery in a specified time with high reliability. The IEEE 802.1 TSN task group is developing standards to provide deterministic communication through IEEE 802 networks. The IEEE 802.1AS standard defines time synchronization mechanism for accurate distribution of time among the communicating devices. The time synchronization accuracy depends on the accurate calculation of the residence time which is the time between the ingress and the egress ports of the bridge and includes the processing, queuing, transmission, and link latency of the timing information. This paper discusses time synchronization mechanisms supported in current wired and wireless integrated systems.