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The Rise of Time-Sensitive Networking (TSN) in Automobiles, Industrial Automation, and Aviation

IEEE Standards Association advances new TSN application profiles as adoption increases across industry sectors

Ethernet is one of the most widely adopted technologies for the transmission of data between devices and is used in many industries because of its speed, affordable cost, and versatility. Over the years, Ethernet standards have evolved to meet increasing needs to transmit more data faster. However, in addition to speed, a key performance factor – determinism – is influencing the increasing need for time-sensitive networking (TSN). 

A deterministic system is a system in which no randomness is introduced in future states of the system, thus allowing a deterministic network to exchange packet data in a precise manner with a defined latency. Because data exchange in Ethernet networks lacks determinism with its packet buffering and varying queuing delays, deterministic data exchange in Ethernet has, until recently, only been possible with proprietary solutions. 

TSN, a relatively new technology, is making Ethernet bridged networks deterministic by design – guaranteed data transport with bounded low latency, low delay variation, and extremely low loss. Today, TSN is notably leveraged in industries where deterministic communication is important, such as automotive, manufacturing, aerospace, transportation, and utilities applications. 

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TSN Standards

TSN is the focus of a series of standards from the IEEE Standards Association (IEEE SA) under development by the IEEE 802.1™ Working Group’s Time-Sensitive Networking  Task Group. The standards define mechanisms for the time-sensitive transmission of data over deterministic Ethernet networks. TSN is not addressed in a single standard. Rather, its collection of capabilities are governed and managed by several separate IEEE standards. TSN uses a profiles approach, which defines the specific set of features, options, configurations, and protocols appropriate for a particular set of TSN applications. Some profiles are well defined, while others are still works in progress.

TSN in the Automotive Industry

Functionality advancements and driver features in today’s automotive systems require high-bandwidth and low-latency in-vehicle communications. Innovation in automotive technology is focused on both hardware and software for an increasing number of applications, including but not limited to adaptive cruise control with stop-and-go, lane departure warning, blind-spot warning, traffic sign recognition, night vision, active headlight system, parking automation, efficient dynamics, hybrid engines, internet access, telematics, online services, Bluetooth integration, local hazard warning, personalization, SW update, and smartphone apps. 

This list goes on and continues to grow with the pace of new, innovative features and, of course, the advent of autonomous vehicles.

Embedded software is a key enabler for advanced functionality and features in automotive systems, which is becoming more complex and requiring increasing amounts of source code. And software complexities lead to more challenges such as requirements for timing predictability and the distribution of software over electronic control units (ECUs), just to name two.

In the automobile sector, Ethernet is the answer for several reasons, including:

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  • Data needs such as raw camera data, data logging, map data, backbone aggregation, high-resolution displays, and in-vehicle Wi-Fi hotspot (carrier link aggregation) wired backhaul;
  • Latency requirements, with the minimum need determined by hardware and the maximum determined by software;
  • Services, including precise time awareness, redundancy/fail-over, and security;
  • More challenging standards for fuel economy, oftentimes by pioneering and using lighter weight materials; and
  • Reduced costs for vehicle manufacture, an underlying reason that cannot be ignored.

To leverage Ethernet, the TSN protocol can precisely guarantee the time certainty of the key signals of automotive Ethernet. Accurate timing and guaranteed data delivery are critical in the automotive environment. IEEE 802.1AS™ provides timing accuracy in the sub-microsecond range, which is required as Ethernet usage grows within the vehicle. In addition, other IEEE and TSN standards provide secure, ultra-reliable, bounded low-latency communications throughout the vehicle at multiple data rates.

Cabling is the third highest cost component in a car, with the engine being first followed by the chassis. Wire harnesses are constructed one at a time, with half of the cost coming from labor. And the wire harness also is the third heaviest component in a car. We can clearly see that reducing the cable weight in a vehicle will directly impact its fuel economy. Thus, because the in-vehicle wiring plant is a tremendous challenge with regards to weight and space coupled with higher throughput requirements for automotive sensors, various PHYs targeting automotive are available today, including 2-wire 10 Mb/s (IEEE 802.3cg™), 100 Mb/s (IEEE 802.3bw™), 1 Gb/s (IEEE 802.3bp™) and 2.5/5/10 Gb/s (IEEE 802.3ch™).

Previously known as the audio video bridging (AVB) series of standards, which are successfully used in automotive infotainment systems today, AVB has evolved into time-sensitive networking in order to reflect the expanded scope of work toward autonomous driving.

In the automotive sector, TSN is leveraged to achieve:

  • Time synchronization—IEEE 802.1AS  maintains synchronized time (+/- 500 nsec worst case) and supports scheduling-bounded low-latency traffic through the network where required while also allowing asynchronous traffic.
  • Very low jitter—IEEE 802.1AS reduces jitter associated with audio/video, command, sensor, and control packet delivery to upper layers.
  • Bounded low latency—Time scheduled traffic (IEEE 802.1Qbv™) and preemption (IEEE 802.1Qbu™) are combined with no need to compress video and other advanced driver assistance systems (ADAS) data (since speeds up to 10 Gbit/s allow multiple channels of high-definition video). As a result, the use of TSN avoids the latency and processing power penalties associated with compressions and decompression.
  • Ultra-reliability—TSN provides reliability in the network (IEEE 802.1CB™ – frame replication and elimination), protection from errant devices (ingress policing), and backup for network timing master (standby GM).
  • Security—Authentication of installed devices (IEEE 802.1AR™ – secure device identity), segregation of traffic types and flows between authorized devices, message integrity, and authenticity are possible.
  • Fast startup—Preconfigured values for timing and bandwidth reservation allows quick startup followed by an optional transition to negotiated values for dynamic adjustments.
  • Faster updates—Firmware updates are quicker with Ethernet’s higher speed.
  • Information sharing—A homogeneous Ethernet network allows instant sharing of information between allowed devices without the delays and security risks associated with interconnecting different bus types through gateways.

TSN in Manufacturing 

A prevalent need for deterministic Ethernet can be found in industrial automation in the ongoing quest to achieve fast, deterministic, and robust communication. While there are several proprietary solutions available, TSN can help standardize real-time Ethernet across the industry.

IEEE 802.1 TSN is an enabler of Industry 4.0, such as the smart factory of cyber-physical systems. TSN is the foundation that provides connectivity and real-time quality of service to time and mission-critical industrial applications on converged networks of operations technology and information technology and converging multiple independent applications in one network, enabling real-time communication on the same infrastructure (cables, bridges). TSN meets these requirements by providing interoperability via open standards. TSN provides synchronization and supports real-time communication, for example, closed loop control over a single standard Ethernet network.

IEEE SA and the International Electrotechnical Commission (IEC) have established a joint project, the IEC/IEEE 60802™ Time-Sensitive Networking Profile for Industrial Automation, so that the right mix of experts is involved in defining the use of TSN for industrial automation. By selecting TSN features and describing their use including configurations and defaults, the IEC/IEEE 60802 standard aims to benefit vendors offering and/or developing TSN products as well as the users of industrial automation technologies.

In smart factories, TSN provides guaranteed data transport with bounded low latency, low jitter, and extremely low data loss. In the manufacturing sector, TSN is leveraged to achieve:

  • Time synchronization—IEEE 802.1AS  maintains synchronized time (+/- 500 nsec worst case) end-to-end, i.e., including the devices running the control applications. Time synchronization is the basis of multiple TSN quality of service (QoS) solutions, e.g., time-based scheduling. 
  • Bounded low latency—TSN includes multiple solutions to provide bounded low latency, e.g., time-scheduling, preemption, and traffic shaping mechanisms. Time synchronization and TSN QoS solutions can reduce packet delay variation (jitter).
  • Resource management—Standard protocols, data models, and interfaces to dedicate resources for time and mission-critical traffic. 
  • Zero congestion loss—TSN provides zero congestion loss via the bounded low latency and the resource management solutions. 
  • High availability/ultra-reliability—TSN provides ultra-reliability and high availability in the network up to seamless communication over redundant paths (frame replication and elimination), protection from errant devices (ingress policing), and backup for network timing master (standby grandmaster). 
  • Security—Authentication of installed devices, segregation of traffic types and flows between authorized devices, message integrity, and authenticity are possible. 
  • Converged network—TSN supports multiple traffic classes that may have very different requirements. Thus, control data traffic in real-time and multiple independent applications using the same network can be carried together with best-effort traffic in the same network infrastructure, increasing the economic feasibility of the network. 
  • Interoperability—TSN leverages the benefits of existing IEEE 802.3 Ethernet, e.g., diagnostics; thus, TSN is applicable in brownfield deployments. A common information model for the network resources enables common TSN engineering and diagnostics. The harmonized interfaces and the protocols for stream set-up support interoperability. Variants should be limited by a harmonized TSN profile for industrial automation,
    i.e., IEC/IEEE 60802, to enable multi-vendor networking to interconnect different bus types used in end stations.

TSN in the Aviation Industry

In the aviation sector, high-bandwidth and low-latency communications are required for technology-rich modern aircraft for avionics, sensors, communications, and entertainment systems, all of which rely on on-board networks. For many years, Ethernet has been the network infrastructure protocol of choice. More recent innovations, notably on commercial aircraft, include advanced avionics systems, onboard Wi-Fi, in-flight entertainment, and connectivity (IFEC) systems, global position system (GPS) data, and more.

IEEE P802.1DP™ / SAE AS6675 is a joint project of IEEE 802 and SAE Avionics Networks AS-1 A2 to define TSN profiles for aerospace. This work will provide a jointly developed standard that serves as both an SAE and an IEEE standard. This standard specifies profiles of IEEE 802.1 TSN and IEEE 802.1 security standards for aerospace onboard bridged IEEE 802.3 Ethernet networks. The profiles select features, options, configurations, defaults, protocols, and procedures of bridges, end stations, and local area networks facilitate the design of deterministic networks for aerospace onboard communications.

Additionally, this standard specifies profiles for designers, implementers, integrators, and certification agencies of deterministic IEEE 802.3 Ethernet networks that support a broad range of aerospace onboard applications, including those requiring security, high availability and reliability, maintainability, and bounded latency.

Conclusion

As TSN continues to gain interest and use across multiple industries, so too does the demand for an increasing number of profiles – the selection and use of TSN tools for specific applications.

Join us in this initiative! The IEEE 802.1 Working Group welcomes participants from academia, government, and industry. We invite those interested in the noted application spaces or in new ones. For more information or to join the standards activity, please visit the TSN webpage at https://1.ieee802.org/tsn. To learn more, follow the latest news about our work at https://1.ieee802.org/category/latest-news. 

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