3.4. Test Standards
To evaluate the effects of TSN on time-sensitive applications and general traffic, test specifications are gradually worked out. The main contributor is OA, which was jointly established by related companies such as NXP, Broadcom and BMW in 2011 and currently has more than 340 members. To apply Ethernet-based communications and TSN to automotive networks, OA formulates and unifies the physical layer, protocol consistency and interoperability specifications of IEEE 100 base-t1, 1000 base-t1 and 1000 base-rh communication methods. OA presents some specifications on the tests of the wiring harness, switch, ECU and other functional requirements, e.g., ECU-level physical layer, data link layer, TCP/IP protocol layer, SOME/IP test specifications formulated by the technology committee (TC) 8, and the automotive wiring harness and connector test specifications formulated by TC 2, and interoperability, compliance, and electro-magnetic compatibility (EMC) requirements and test methods for 10 BASE-T1 PHYs standardized by TC 14.
Most of the 14 TCs of OA focus on the PHY layer, protocol consistency and interoperability, which are the basis of TSN implementation. The TC focusing on the TSN protocol test itself is TC 11, which creates specification and qualification requirements for Ethernet switches. In detail, TC 11 defines functional features for switch semiconductors (standalone or built-in), and gives the interfacing, configuration diagnostics and monitoring of switches, which can be used for TSN test. In addition, TC 11 specifies tests on TSN requirements and characteristics, such as QoS requirements, queuing, time stamping, policing, and filtering [
50]. In TC 11 [
50], the requirements and test points of switches are specified. For example, it indicates that the Ethernet switch shall support at least eight different levels of priorities according to IEEE 802.1Q and provide a queue for each priority on each egress port to support different QoSs of TSN. The Ethernet switch can overwrite the priority of a frame at an ingress port independent of the incoming priority (i.e., support global priority overwrite). Incoming priorities shall be freely mapped to internal queues by the ingress filter. Frames of internal queues shall be freely mapped to priorities according to IEEE 802.1Q [
43] on the egress port. For each queue at the egress port, it has a shaper to schedule frames. The shaper supports strict priority scheduling and the CBS algorithm according to IEEE 802.1Qav [
30]. And each queue can deactivate each shaper individually to cancel TSN scheduling. For time synchronization, TC 11 specifies that the Ethernet switch should support both the PTP 1588 protocol and IEEE 802.1AS [
26] protocol. In addition, each port should synchronize with each other. For the diagnostics and robustness, the Ethernet switch shall provide at least the following counters individually for each port: number of received frames, number of received bytes, number of dropped frames after reception, number of sent frames, number of unsuccessful sent frames, number of sent bytes, and maximum fill level of the queues since clearing the counter.
In [
50], TC 11 also provides a collection of all test cases which are recommended to be considered for automotive use cases and should be referred by car manufacturers within their quality-control processes. In detail, it presents the test procedures of time synchronization based on TSN, which checks the 1-step frame forwarding mechanism, including the correct implementation of residence time measurement. The test station sends sync frames to the PTP slave port and receives frames on all PTP master ports of the device under test (DUT). The corresponding time stamps of the test station are recorded. The correction time of the sync message is checked if the value correlates to the timestamp measurements of the test station. In addition, it checks whether the switch supports priority-based QoS or not by using all eight possible values. The strict priority algorithm is utilized as a forwarding selection mechanism in order to verify that forwarding is based on priorities.
4. TSN-Related Products
Early TSN products were generally used for industrial automation with the realization of main protocols, such as EEE 802.1AS [
26], IEEE 802.1Qav [
30], and IEEE 802.1Qat [
35]. With the development of TSN and autonomous driving, some TSN products for automotive are designed. Active manufacturers in this area mainly include TTTech, Microchip, NXP, Excelfore, Broadcom, Marvell’s, Spirent, etc.
In terms of TSN switch chip, a NXP product, NXP sja1110, is the first automotive Ethernet switch, which was designed to solve the huge challenges faced by current in-vehicle networks, including scalability, reliability, security, and high-speed traffic engineering. This switch complies with the AVB/TSN synchronization standard. In addition, NXP designed the SJA1105T chip, which is a core of multi-functional product. This switch chip supports a network with standard Ethernet, which not only supports best-effort business but also QoS-required traffic by using TSN for clock synchronization and time-aware shaping. The Microchip Corporation designed a series of Ethernet switches, such as KSZ8565, KSZ8765 and KSZ8842, which support TSN characters, including IEEE 1588 v2 PTP. Broadcom BCM8956X series devices are Broadcom’s fifth-generation fully integrated L2+ multilayer switch solution, which supports AVB protocol stack (IEEE 802.1AS [
26] time synchronization and IEEE 802.1Qat [
35]). Except for the realization of the basic specifications of AVB, Marvell developed a series of products with more TSN specifications. For example, the switches 88Q5072 and 88Q6113 of Marvell addeds TSN features to achieve the filtering and control of data streams (IEEE 802.1Qci [
37]) and frame preemption (IEEE 802.1Qbu [
28]). The integrated L3 hardware accelerator allows a gigabit routing throughput of up to 10 Gbps to be achieved without internal processor intervention. To promote big data transmission in the vehicle network, these devices provide efficient sleep/wake functions that support the TC 10 standard, reducing the overall power consumption. Marvell 88Q5050 is an eight-port, high-security automotive gigabit Ethernet switching chip, which has advanced security features to prevent cyber threats, such as DoS attacks. The eight-port Ethernet switch chip has four fixed IEEE 100 BASET1 [
22] ports and four configurable ports. The switch chip provides local and remote management functions, and users can easily access and configure the device.
In terms of the TSN protocol stack, Excelfore eAVB/TSN now runs in cameras, video displays, head units and ECUs from numerous vendors. The Excelfore eAVB/TSN has already been ported to automotive-grade operating systems, including Linux, Mentor automotive open system architecture (AUTOSAR) and Green Hills Software INTEGRITY [
51]. The Excelfore protocol stacks integrated and optimized for use with the safe and secure INTEGRITY RTOS from Green Hills Software [
51], including support for Ethernet AVB/TSN Talker/Listener, DoIP, SOME/IP, and RTP/RTCP (including IEEE 1733) and 802.1AS [
26] slave/bridging.
In terms of TSN testing, TTTech designed a combination switch ECU called DESwitch Hermes 3/1 BRR, which is used for evaluating a variety of communication standards, including AVB, TSN and time-triggered Ethernet (SAE AS6802). With these technologies, users can evaluate the convergence of Ethernet control traffic, including security applications and the vehicle backbone architecture. Polelink developed a TSN test tool for automotive Ethernet called the TSN box. This TSN box is a network interface and gateway for TSN network. It was developed based on field programmable gate array (FPGA) technology to serve as a data collection medium for TSN tools, which supports nanosecond timestamps for time synchronization among multiple TSN boxes.
In addition, the TSN box provides rich functional support for AVB and TSN protocols commonly used in automotive Ethernet architectures, which can be used for exploring PTPv2, 802.1ASrev [
27] and different TSN shaping algorithms, such as CBS, time-sensitive or asynchronous shaping. Xinertai launched an automotive Ethernet test program based on the proprietary BigTao hardware test platform. Cooperating with Xinerta’s software Renix [
52], the Ethernet test program can realize Layer 2–7 traffic test and protocol simulation for automotive Ethernet, support 100/1000 Base-T1 port connectivity test, RFC2889/RFC2544/RFC3918 standard test suite, routing and switching protocol testing, AVB/TSN protocol testing, distributed denial-of-service (DDoS) attack testing, long-term (such as
10*2410*24 h) stability and streaming testing, etc. Spirent issued the AUTOSAR conformance test suite pack, which provides different protocol conformance test suites according to the OA test specification. Through this test suite, automotive Ethernet tests can be run on Spirent C1 and C50 devices, which supports testing on clock synchronization and 802.1 Qav [
30] scheduling of TSN.
For the vehicle Ethernet PHY chip, it must firstly meet the IEEE 802.3bw or IEEE 802.3bp protocol, and then must pass the AEC-Q 100 standard. The existing semiconductor manufacturers that have launched automotive Ethernet PHY chips include BCM 89610, BCM 89611, BCM 8988X, BCM 89810, BCM 89811 and BCM 89820 of Broadcom, AR 8031 of Artheros, TJA 1100, TJA 1101 and TJA 1102 of NXP. For example, NXP TJA 1101 is based on the IEEE 100 BASE-T1 standard, with the single-port Ethernet PHY transceiver. NXP TJA 1101 meets the needs of automotive applications and supports 100 Mb/s transmission, and its receiving capacity is over 15 m of the unshielded twisted pair. TJA 1100 can achieve the lowest system cost, and meet the strict restrictions on area and heat dissipation of the sensors of the new generation of ECU and ADAS. It complies with AEC-Q 100 level 1, and the original design intention has the smallest package size, the lowest external component overhead and low power consumption.
5. Demo Setup of TSN
To realize basic functions of TSN and provide a deterministic network for autonomous driving, the least complete set of standards to be realized should be considered. The complete set of most TSN products is usually constructed by standards of AVB, i.e., 802.1AS [
26], 802.1Qav [
30], and 802.1Qat [
35], which are mainly used for A/V streams.
Safety-relevant devices, such as multiple kinds of sensors, need synchronization with each other to infuse them. In addition, synchronization is the preliminary step of many scheduling and management schemes. Thus, the 802.1AS [
26] specification needs to be realized first. To provide deterministic transmission for critical traffic, such as the control comment, bandwidth reservation is needed. On the other hand, the traffic class is finite and fixed, compared with that of industry. Thus, a preferred bandwidth reservation method is pre-allocating the bandwidth for different application traffic instead of 802.1Qat [
35] to reduce the signaling overhead and related information storage brought by the stream register of 802.1Qat. Correspondingly, a scheduling method is needed for bridges and end stations to queue and forward frames with different classes. 802.1Qav [
30] is preferred for data transmission within a domain. For data transmission among multiple domains, 802.1Qbv [
31] is an alternative method. In addition, 802.1CB can provide a baseline for giving redundant paths and supporting robustness. 802.1Qcc [
36] can provide corresponding configuration for these protocols. Other specifications can be further realized for a more robust and deterministic network. The basic TSN protocol stack model of the switch of in-vehicle networks is shown in
Figure 4, where blue blocks construct a minimum complete set of standards to be realized for a TSN-supported bridge of automotive networks. The end station can be seen as a bridge with a port.
Figure 4. A basic TSN protocol stack model of automobile networks.
For the TSN demo set up, the above functions are expected to be examined and displayed. Here, a demo setup for some typical functions is given, such as that of 802.1AS, 802.1Qbv, and 802.1CB, which is shown in Figure 5.
Figure 5. A demo setup for some typical TSN functions.
As shown in this figure, synchronization is examined by observing whether two A/V traffic generators are synchronized or not. They can be two AVB cameras recording the same view. In Display 1, it shows the views of two cameras, respectively. When they are synchronized, the displayed views of the two cameras are the same. This is an intuitive show. More accurately, it can be tested by using time-record software. Two cameras photograph the software with the time display and transmit them to DCU 1. Then, whether the transmitted pictures with time are the same or not can be seen. 802.1Qbv [
31] is checked by using three traffic generators, i.e., A/V traffic, best-effort traffic and control traffic. With the interfering traffic (BE traffic and A/V traffic), the delay and jitter performance of control traffic can be observed, which should not be affected by the interfering traffic and have guaranteed latency and low jitter based on Qbv. For the 802.1CB demo, redundant routing is used for critical traffic. The robustness of the traffic transmission can be observed by allowing routing congestion with abundant traffic.
The simulation environment developed here is based on FPGA, and the PHY chip is Realtek RTL8201CP, which has a clock frequency of 25 MHz at 100 Mbps, i.e., the clock accuracy is 40 ns. The corresponding waveforms were obtained and analyzed experimentally.
As shown in Figure 6, the vertical coordinate time offset represents the time deviation between nodes measured at each time in μs, and the horizontal coordinate time represents the time-synchronization interval, which is 1 s. After a short period of jitter at the beginning of the time synchronization, the time deviation between nodes tends to converge; the final value of this time-synchronous convergence converges to 14.5 μs. The simulation experimental results show the effectiveness of the time synchronization, which shows that AS is feasible in the demo setup.
Figure 6. Time offset between two nodes.
In Figure 7, the vertical axis end-to-end latency represents the total time it takes for a data packet to be sent from the sender to the receiver, measured in microseconds (μs). The horizontal coordinate sampling times indicates the number of times the data are sampled at the same time interval. The impact of enabling the time-synchronization feature on the traffic-scheduling performance of the TAS algorithm is verified by comparing with and without enabling time synchronization, and the results show that the end-to-end delay of traffic is reduced by an average of 80 μs when time synchronization is enabled. In addition, simulation experiments show that Qbv achieves end-to-end low latency performance under time synchronization, which also validates the effectiveness and feasibility of the demo setup.
Figure 7. End-to-end delay of traffic transmission.
In Figure 7, the vertical axis end-to-end latency represents the total time it takes for a data packet to be sent from the sender to the receiver, measured in microseconds (µs). The horizontal coordinate sampling times indicates the number of times the data are sampled at the same time interval. The impact of enabling the time-synchronization feature on the traffic-scheduling performance of the TAS algorithm is verified by comparing with and without enabling time synchronization, and the results show that the end-to-end delay of traffic is reduced by an average of 80 µs when time synchronization is enabled. In addition, simulation experiments show that Qbv achieves end-to-end low latency performance under time synchronization, which also validates the effectiveness and feasibility of the demo setup.
6. Open Issues and Trends
In general, TSN is an emerging technology, for which many problems need to be solved. In this section, several promising research directions with respect to TSN are discussed as follows. This section discusses the challenges and open issues in time-sensitive networking (TSN), first highlighting the need for a grand master and a comprehensive resource allocation and scheduling plan and discussing the advantages and disadvantages of centralized and distributed scheduling methods, as well as highlighting the importance of an efficient and flexible network solution to support real-time applications in the automotive industry.
6.1. Synchronization
An open aspect of time synchronization is the efficient choice of the grand master (GM). GM provides the reference time for other devices of the network. However, the
standardized BMCA needs frequent information exchange and comparison to select the best clock among all devices and ports. This will bring much overhead cost and it is against the reduction in latency. Specially, the main current forwarding and queuing schemes are dependent on the synchronization time. Therefore, this GM selection ultimately affects the efficiency and results of scheduling. For the automotive network, it usually has simple and static topology with known clock accuracy of its devices. It is an alternative method to pre-designate a GM. However, the damage of GM under this situation will lead to non-synchronization and failure to implement TSN. Preparing some alternative GMs may be a potential approach to solve this problem. How to specify a GM and determine the number of alternative GMs needs to be further studied.
6.2. Resource Management
The main specified bandwidth reservation protocol is provided in 802.1Qat [35], which gives a decentralized stream registration and resource reservation procedure. However, any new arrival, leaving, or new requirements of streams will lead to signaling exchanges along the transmission path of the streams. This overhead becomes significant with the increases in hops. Thus, it cannot provide strict transmission latency for critical traffic. To overcome this shortage, 802.1Qcc [36] provides a way to control the network globally. But it is still unclear as to how to appropriately allocate resources to all traffic with different priorities in the network from a global view instead of only allocating resource to critical traffic. A comprehensive resource allocation plan is conducive to the efficient use of all resources and minimizing the loss of non-critical services. In addition, although 802.1Qcc [36] provides a possibility of allocating resources with the consideration of scheduling, a joint resource allocation and scheduling approach needs to be further studied. Without considering scheduling, the resource allocation scheme cannot be efficiently realized by queuing and forwarding. Last but not the least, efficient resource allocation should consider the link state and the traffic character. Static resource allocation for different traffic classes with fixed allocated bandwidth ratios not only induces resource waste but also is harmful for guaranteeing the transmission latency of critical traffic, especially for bursty data or busy networks.
6.3. Scheduling
Scheduling methods are the core of current TSN specifications and studies. With scheduling, it not only eases bursty traffic and reduces network congestion but also queues and forwards different traffic reasonably according to their importance. Related scheduling methods can be divided as centralized and distributed. Distributed scheduling will not strictly schedule traffic by obeying the allocated bandwidth. Therefore, its scheduling only obeys the reserved bandwidth, softly leading to latency exceedance, especially for a topology with multi-hops. In addition, information exchange also brings abundant overhead for dynamic topology or long path. For automotive applications, some unexpected traffic, such as the braking command, requires urgent transmission, which also brings the program of resource allocation and scheduling. A distributed scheduling is not efficient in such cases. In contrast, centralized scheduling can schedule traffic without frequent information exchange and schedule all nodes along the path simultaneously. However, the selection, deployment, and robustness of the central node will affect the scheduling results significantly. How to balance the advantages of both types of scheduling methods is an open issue. In addition, the queuing of different traffic is separate which may use different scheduling schemes. A unified scheduling is better for improving the scheduling efficiency. For example, we study how to unify the Qav, Qbv, Qch, strict priority and asynchronous schemes used in the egress port. Thirdly, different types of traffic have different latency requirements. Although the TAS is a novel feature for the ultra-low-latency transmission of time-critical traffic, it has high implementation complexity and additional overhead due to the GCL schedule generation/deployment and time synchronization. Moreover, it is unsuitable for aperiodic traffic flows. Different scheduling methods should be used for different types of traffic. For example, for periodic traffic, more static scheduling, such as time-triggered scheduling, can be used. For sporadic periodic traffic, how to efficiently schedule is a study direction. Lastly, the current time-triggered scheduling can be preempted by time-sensitive applications designed in the specification. However, the efficiency of this preemption should be investigated especially for the busy network scenario. In the resource allocation method, non-critical traffic is originally allocated less bandwidth. The preemption of the guarded bandwidth by critical traffic may be trivial. Hence, an important future work direction is to develop traffic transmission schedules with reduced numbers of guard band occurrences in order to prevent wasted bandwidth and to keep latencies low. Scheduling based on traffic predication and being more flexible may be expected.
6.4. Configuration
The configuration models can be divided into centralized and distributed groups. The hybrid configuration which also supports existing distributed resource allocation methods, such as the stream registration of 802.1Qat as a research direction. In the hybrid configuration, the centralized node can provide configuration in time and optimize performance from a global view, while distributed nodes can cooperate with the configuration in case the centralized node is out of work. Even so, the configuration cost and time still need to be studied for reduction. This is because that higher configuration cost will occupy higher limited bandwidth, and longer configuration time induces longer time delay for critical traffic. Therefore, the communication and computation requirements should be considered for the configuration node design and selection. In the future zone architecture of the car, the domain controller may be a candidate for the configuration node. Traditionally, the in-vehicle network is configured statically at the designed time to guarantee the quality of service (QoS) requirements of the applications. Due to the static network configuration, it is normally difficult to introduce new applications during the lifetime of the vehicle. The need for an IVN supporting dynamic traffic will increase as the number of features and functionalities requiring dynamic traffic handling in the vehicle increases. Some of the dynamic applications are vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I) and vehicle-to-network (V2N), adaptive cruise control, truck trailer systems and over-the-air (OTA) software updates [53]. Therefore, automotive applications require dynamic reconfiguration facilities to meet the requirements of new evolving features. Several studies suggest that complementing TSN with a networking concept, such as software-defined networks (SDNs) is a beneficial configuration solution [54–56]. With additional protocols (e.g., Netconf and Openflow), SDN allows for the instant configuration of routes and transport schedules based on a central control plane. It also allows splitting up flows for transmission on multiple paths for load balancing, using the available bandwidth more efficiently, and making network-wide configurations, such as time synchronization.
6.5. Robust and Certainty
It is clear that there is a trade-off between transmission certainty and resource cost. For example, 802.1CB [38] uses redundant transmission to improve the successful transmission probability of critical traffic. The obtained end-to-end topology is helpful for the relay to determine the redundant paths. This topology cannot be obtained by each relay of 802.1CB. Although 802.1Qca can pre-define redundant paths for each stream, it cannot intelligently determine the redundant paths based on the available bandwidth and the requirements of other applications. This will lead to a lack of enough conditions for executing redundant transmission. This problem is especially serious for distributed redundancy schemes, such as 802.1CB due to the lack of topology information. On some congestion paths, the replication of packets will bring more burden to some links, leading to uncertainty and high latency. Although some alternative links may successfully transmit packets of stream, packet transmission on the congestion link only aggregates this condition without improving the robustness.
6.6. Ongoing TSN Standards
There is a special standard draft, IEEE P802.1DG [57], which describes the TSN profile for automotive Ethernet communications. This standard specifies profiles for secure, highly reliable, deterministic latency, automotive in-vehicle bridged IEEE 802.3 Ethernet networks based on IEEE 802.1 TSN standards and IEEE 802.1 security standards [21]. This standard provides profiles for designers and implementers of deterministic IEEE 802.3 Ethernet networks [53] that support the entire range of automobile applications including those requiring security, high availability and reliability, maintainability, and bounded latency.
In addition, scheduling independent of synchronization is also an open issue. Current standardized scheduling methods need synchronization among network nodes, while the synchronization affects the scheduling performance. IEEE P802.1Qcr [33] is a specification draft on asynchronous traffic shaping (ATS), which operates asynchronously, i.e., bridges and end stations need not be synchronized in time. The ATS is originated from the urgency based scheduler (UBS) [58], which implements a per-flow interleaved regulator [59] based on rate-controlled service disciplines, providing deterministic latency with low implementation complexity. In the provided asynchronous traffic shaping method, it prioritizes urgent traffic over relaxed traffic. Thus, ATS can utilize the bandwidth efficiently, even when operating under high link utilization with mixed traffic loads, i.e., both periodic and sporadic traffic. By using these queuing and forwarding schemes, not only the latency of time-sensitive traffic can be reduced and guaranteed but also the stream arrival can be smoothed, as a result of which the network congestion can be reduced. As future research direction, one relevant one is the IEEE 802.1Qcr-2020 [33] standard, which is very promising, as it offers bounded latency asynchronous shaping with robustness properties (e.g., integrated policing) and permits compositional timing analysis.
This draft also specifies an information model for the capabilities of asynchronous traffic shaping. It further specifies a YANG data model and management information base (MIB) modules to support configuration and status reporting. Additionally, it provides an informative framework for the delay analysis of the worst case in static networks with static configurations. It also addresses errors and omissions in the description of the existing functionality.
IEEE P802.1Qdd [60] specifies protocols, procedures, and managed objects for a resource allocation protocol (RAP) that uses the link-local registration protocol (LRP). It supports and provides backwards compatibility with the stream reservation and QoS capabilities, and controls and protocols specified in IEEE Std 802.1Q [43]. RAP provides support for accurate latency calculation and reporting, which can use redundant paths established by other protocols and is not limited to bridged networks.
IEEE P802.1Qdj [61] provides configuration enhancements for TSN. In this specification, it defines procedures, interfaces, and managed objects to enhance the three models of TSN configuration. It specifies enhancements to the user/network interface (UNI) to include new capabilities to support bridges and end stations in order to extend the configuration capability. It preserves the existing separation between configuration models and protocol specifications.
IEEE P802.1ASdm [62] amends 802.1AS to specify the hot standby protocol, process and management objects that do not use the BMCA for the time-aware system. P802.1ASdm includes the function of converting the synchronization time of the two general precision time protocol (gPTP) domains into a synchronization time for the application programs, the function of directing the synchronization time of one gPTP domain to another gPTP domain and a mechanism to determine whether the gPTP domain has sufficient quality for hot standby.
For the transmission redundancy, IEEE P802.1CBcv amends IEEE Std 802.1CB [38], which provides FRER extended stream identification functions, including process and
management objects for adding new stream recognition functions.
6.7. TSN Based on Wireless Channel
Except the research points specified in published and ongoing standards, TSN based on wireless channel is attracting more attention, especially for Industry 4.0 since wireless connectivity can enable flexibility, scalability, and lower costs in next-generation factories. The 802.1AS [26] time synchronization based on wireless channel has been designed, while more designs are needed for the accuracy and timeliness of the synchronization. Currently, because a 5GS does not provide time synchronization between the user equipment (UE), radio access network (RAN), and user plane function (UPF), a new time-synchronization mechanism is required. In addition, a new buffering and scheduling mechanism is required for processing TSN traffic because guaranteeing a deterministic delay as well as a low delay is necessary. In addition, different from wire communications, the broadcast character of wireless communications will bring interference among nodes. Therefore, the reduction in robustness should be considered. Correspondingly, resource management, channel access, scheduling, configuration and security need to be future investigated. The WLAN can be used for TSN besides 5GS. However, because WLAN cannot detect collisions, it uses a random back-off counter to avoid collisions. The random back-off mechanism increases the transmission delay and causes high jitter. Thus, maintaining the delay within a particular range is challenging.
For automotive applications, since Ethernet is the most promising in-vehicle backbone network technology, the TSN based on wireless communication may be future work. For the deterministic and low-latency transmission of inter-vehicle networks, TSN investigation is needed for wireless and 5G techniques.
6.8. TSN Products
Although many TSN products, from the physical layer to the application layer, were designed, most of them are used for the deterministic transmission of Industry 4.0. For automotive networks, some preliminary products were developed, most of which realized standards of AVB, such as 802.1AS, 802.1Qav and 802.1Qat. For TSN, some products realized the protocol stack for testing. More products with integrated TSN characters are needed, which can be used for automobiles to guarantee deterministic transmission for the critical traffic of intelligent driving.
7. Conclusions
In this paper, we presented an in-depth survey of time-sensitive networking (TSN) for intelligent driving. We introduced TSN-related standards specified by the Institute
of Electrical and Electronics Engineers (IEEE) 802.3 work group (WG), IEEE 802.1 WG, Internet Engineering Task Force (IETF) and OPEN Alliance (OA) from the physical layer to the network layer to enable Ethernet to provide deterministic, low-latency and high bandwidth data transmission for emerging applications brought by intelligent driving. Furthermore, we revealed corresponding automotive products based on these TSN specifications. In addition, we analyzed a minimum set of specifications that should be considered to realize TSN functions for automotive applications, based on which we presented a demo setup. Based on our survey, we concluded the existing techniques of TSN, and identified corresponding solutions and proposed potential solutions to address these issues. We also gave some promising techniques and ongoing standards of TSN, including new designs of synchronization, configuration, robustness, resource allocation and the TSN based on the wireless channel, followed by a discussion of its feasibility for automotive applications. With the aid of this survey, researchers can obtain a quick understanding of the contents, progress and challenges of TSN on automotive networks. Furthermore, developers of TSN can draw lessons from solutions provided in this paper both in term of theory and practice.
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