Hardware assisted clock synchronization with the IEEE 1588-2008 precision time protocol

Emerging technologies such as Fog Computing and Industrial Internet-of-Things have identified the IEEE 802.1Q amendment for Time-Sensitive Networking (TSN) as the standard for time-predictable networking. TSN is based on the IEEE 1588-2008 Precision Time Protocol (PTP) to provide a global notion of time over the local area network. Commonly, off-the-shelf systems implement the PTP in software where it has been shown to achieve microsecond accuracy. In the context of Fog Computing, it is hypothesized that future industrial systems will be equipped with FPGAs. Leveraging their inherent flexibility, the required PTP mechanisms can be implemented with minimal hardware usage and can achieve comparable synchronization results without the need for a PTP-capable transceiver. This paper investigates the practical challenges of implementing the PTP and proposes a hardware architecture that combines hardware-based time-stamping with a rate adjustable clock design. The proposed architecture is integrated with the Patmos processor and evaluated on an experimental setup composed of two FPGA boards communicating through a commercial-off-the-shelf switch. The proposed implementation achieves sub-microsecond clock synchronization with a worst-case offset of 138 ns.