Time-Sensitive Networking (TSN) is a set of standards created by the Institute of Electrical and Electronics Engineers (IEEE) to enable traditional Ethernet networks to be used in deterministic, safety-critical applications in environments like automotive.
Ethernet is the industry standard technology for wired computer networking, but it was not designed for predictability. It is based on the concept of “best effort.” When Ethernet traffic encounters congestion, units of data — called frames — can get buffered, shunted into queues or sometimes dropped and retransmitted, which is typically good enough when you are opening emails or sending documents to a colleague.
There is no method within traditional Ethernet to create traffic that is deterministic — that is, traffic that gets from point A to point B within a set amount of time. One of the original use cases for deterministic networking was the transmission of audio and video, which sound choppy or look jumpy when there is too much of a time delay between the transmission and reception of data packets.
In 2012, the IEEE Audio Video Bridging Task Group was renamed the Time-Sensitive Networking Task Group and adopted a broader focus due to the increasing demand for deterministic Ethernet, including in automotive use cases like advanced driver-assistance systems. If a vehicle is engaged in a complex safety-related action, such as lane correction or emergency braking, the system cannot afford even the slightest delays or gaps in data transmission.
TSN provides timing accuracy within 1 microsecond and delivers predictable latency and guaranteed bandwidth. IEEE developed the P802.1DG — TSN Profile for Automotive In-Vehicle Ethernet Communications standard specifically for automotive applications.
How does TSN work?
The first challenge for IEEE was injecting the concept of time into the Ethernet standard; deterministic networking works only if all connected devices — including endpoints, switches, bridges and gateways — share a common clock.
Once all of the devices have been synchronized, a controller manages processing and forwarding communication packets, scheduling and prioritizing traffic, selecting communication paths and reserving bandwidth and time slots.
By implementing TSN, OEMs can achieve wired communication with low packet delay variation, low packet loss and bounded low latency; in other words, the total delay experienced by data traversing the network can be guaranteed not to exceed the predetermined value.
Benefits of TSN in automotive
All of the innovations associated with the software-defined vehicle rely on real-time transmission of data over wired networks. TSN is the underlying networking technology that ensures that data moves back and forth from sensors, cameras, radar, diagnostic systems and infotainment platforms to electronic control units and onboard computers in a secure, reliable, timely and predictable fashion. Ethernet is also far less expensive than proprietary solutions.
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