How to achieve the higher accuracy of in real-time data transfer in automotive system?
Applications such as audio-video, motion sensing, parking assistance and automated driving all need distributed real-time data transfer. A clear trend is emerging, with the migration towards full in-car Ethernet networks and away from point-to-point and ring topologies from CAN and MOST systems respectively. This is due to the benefits an Ethernet network affords in reduced weight and simplified connections, all whilst maintaining accurate data transferral and the potential for new capabilities.
IEEE 802.1 is a ‘living’ set of standards, continuing to develop to serve the needs of Time-Sensitive Networks by providing techniques to deliver accurate synchronisation, deterministic latency and controlled bandwidth. Clearly, accurate synchronisation is one of the key factors for a network implementation. The higher the level of synchronization that can be guaranteed through networks and devices, the better the potential end performance, which is especially important in safety-critical aspects of automotive systems.
gPTP, developed from the Precision Time Protocol (PTP), is one of the solutions for achieving high-accuracy time synchronisation in ethernet environments. PTP provides benefits such as multiple clock paths for added redundancy to ensure accurate time is maintained in failover conditions. Specifically, gPTP also makes use of a logical syntonization technique that can lock and maintain accurate timing through a system within seconds; this facilitates the “fast turn-on” capability required in an automotive system. This mechanism is further defined in the IEEE 802.1AS/AS-REV standards.