## 1 Introduction and motivation
However, AVB was not still enough for the time-critical and safety-critical flows typically found in industrial and automotive applications (e.g., advanced driver assistance systems, automated driving), which require deterministic communications and very high reliability. To remedy such short-comings, the Time-Sensitive Networking (TSN) standards were introduced to provide such properties. TSN is a family of standards which tackle several aspects. Among them are reliable time synchronization [24], support for scheduled traffic (ST), i.e., a traffic class that requires to be transmitted following a given timing [25], per-stream filtering and policing [26] (both enrolled in the IEEE 802.1Q standard [27] since 2018), frame replication and elimination mechanisms to improve reliability, and many others. As the TSN standards are a flexible toolkit, the network designer can pick the features and mechanisms that match the requirements of the context under consideration and combine them in a modular design, also leveraging the IEEE 802.1 Qcc [28] standard for configuration purposes, to fulfill the requirements of diverse application contexts, e.g., industrial, consumer, and automotive. Another interesting step forward in dealing with RT traffic over TSN networks for in-car communications is a recent online approach that, instead of statically binding each flow to a given traffic class, handles all the frames, both periodic and event-driven (ED), according to the Earliest Deadline First (EDF) scheduling algorithm. The motivation for such a deadline-aware approach, called Deadline-TSN (D-TSN) [29], is that it allows to deal with periodic and event-driven RT frame online and in a uniform way. D-TSN applies an EDF-based approach, which is implemented by leveraging the IEEE 802.1 Qci standard on each hop in their path from the source to the destination. D-TSN offers several benefits. First, it is an online scheduling approach, and therefore it does not require offline schedule calculations. Second, as multiple priority levels are available, it is able to support several classes of RT event-driven traffic. Finally, it maintains the standard Ethernet frame format, and therefore it does not introduce any additional frame overhead. What is missing in D-TSN is the support for ST. For this reason, this work proposes an approach, called Deadline-ST (D-ST), which builds upon D-TSN and extends it in a way that combines the flexibility offered by online deadline-aware scheduling with the support for ST. The main contributions of the paper are the following:  
* The detailed design of D-ST, which allows for transmitting periodic, RT event-driven, and scheduled traffic within a common framework. * A simulative assessment of D-ST in a realistic automotive scenario. The progress beyond the state of the art is that D-ST is able to combine in a single framework three important properties for automotive communications, i.e., (i) the ability to flexibly provide multiple priorities to RT event-driven frames, through online EDF per-frame scheduling, (ii) the ability to guarantee the temporal isolation for time-driven flows, and (iii) the full compliance with the TSN standards. With D-ST, the diverse automotive RT traffic types can obtain the best service from the network without the need for hardware modifications in the Ethernet switches, and this is what the current research on TSN-based automotive communications is mainly striving for. In this context, D-ST is, therefore, a feasible and appropriate solution for automotive communications over TSN networks. The structure of the paper is the following. Section 2 recaps the relevant literature. Section 3 outlines the TSN standard mechanisms exploited by D-ST. Section 4 describes the D-ST design, and Section 5 presents simulative assessments of D-ST. Finally, Section 6 concludes the paper and outlines further research threads.