University of Twente Student Theses


Synchronization improvement in automotive Ethernet networks

Chatzimichail, Kyriakos (2023) Synchronization improvement in automotive Ethernet networks.

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Embargo date:20 October 2028
Abstract:This thesis presents a study on the generalized Precision Time Protocol (gPTP), which is standardized by IEEE in 802.1AS and it is responsible for time synchronization over Ethernet networks, and tries to improve its performance. Ethernet is set to become the leading architecture of automotive networks for a number of advantages over the legacy architectures that include CAN, LIN, and FlexRay. In the earlier years Ethernet was not used in automotive, mainly due to its non-deterministic nature. The emergence of Time Sensitive Networking (TSN), though, aims to make Ethernet deterministic and suitable for time-critical applications, with a set of standards, including gPTP. This thesis aims to analyze and improve gPTP in terms of the time intervals between the messages that the devices exchange, the data rate, and the physical layer (PHY) latency. gPTP is a message-based protocol that ensures that all the devices of a network have a common notion of time. A Grandmaster is responsible for initiating the synchronization mechanism by sending messages that contain time information. These messages are relayed by bridges and reach all the end stations, which can update their time with the new information. In order to take into account the delays along the path, every device initiates the peer-to-peer delay mechanism in order to calculate the path delays with its neighbors. The thesis is divided into two parts: lab measurements and simulations. The lab measurements consist of measurements on an actual automotive Ethernet switch (SJA1110 of NXP). The performance of the protocol is tested with respect to the message intervals, the data rate, and the PHY latency. The metrics used to assess its performance is the clock jitter, the CF Accuracy, the Pdelay Turnaround Time Accuracy, and the NRR Accuracy. The second part consists of simulations that focus on the effect of PHY latency on the performance of the protocol. First, the theoretical contribution of PHY latency to the synchronization inaccuracy is proven. Finally, a way to mitigate the effect of PHY latency and improve the performance of gPTP is suggested.
Item Type:Essay (Master)
NXP Semiconductors, Eindhoven, Netherlands
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:50 technical science in general, 54 computer science, 55 traffic technology, transport technology
Programme:Electrical Engineering MSc (60353)
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