TSN Scheduling for Deterministic Control over 10BASE-T1S in Zonal Automotive Architectures

Abstract

Time-Sensitive Networking (TSN) is a key mechanism for deterministic in-vehicle Ethernet, but its end-to-end behavior over 10BASE-T1S shared media remains unclear under mixed traffic in zonal architectures. This paper experimentally evaluates periodic control traffic delivered from an upper zonal Ethernet TSN domain to a lower-tier 10BASE-T1S bus. The testbed connects two cascaded SJA1110-based switches and an EVB-LAN9383 switch to a 10BASE-T1S motor-control node, with best-effort (BE) background traffic generated by an internal processing core of the second SJA1110. Control latency is measured by matching a 32-bit sequence field between source-side Ethernet and destination-side 10BASE-T1S observation points while varying BE load from 0% to 95%. We compare No GB, which strictly separates scheduled traffic (ST) and BE traffic without a guard band; fixed guard-band (GB), which closes the cycle end before the next ST window; Shared, which opens the remaining non-ST interval to both ST and BE traffic; and two ST-slot/GB-width variants. The results show that No GB suffers severe latency growth, whereas fixed GB stabilizes lowand medium-load latency near 3 ms but loses matched delivery under high load. Shared provides the best control-delivery tradeoff in the evaluated testbed, maintaining above 95% matched ratio through $\mathbf{9 0}$ % load with $\mathbf{5 1 0. 8} \mu \mathbf{s}$ and $\mathbf{6 7 8. 3} \mu \mathbf{s}$ mean latency at 0% and 90%, respectively. These results indicate that flexible shared scheduling can improve control-flow delivery compared with strict static partitioning in the evaluated 10BASE-T1S-based zonal topology, while BE fairness and synchronization-related phase effects require further study.