Automotive Ethernet

Automotive Ethernet provides high-bandwidth, scalable networking for cameras, ADAS, infotainment and backbones. Learn single-pair PHYs (100BASE-T1, 1000BASE-T1, multi-gig), switches and VLANs, TSN for determinism, SOME/IP and DoIP protocols, bandwidth calculations and zonal architectures.

A single ADAS camera can produce more data than an entire CAN network can carry in a second. Automotive Ethernet brings the internet's networking technology into cars on a single twisted pair — 100 Mbit/s to 10 Gbit/s.

It's the backbone of software-defined vehicles: zonal controllers, central computers, OTA updates and fast diagnostics.

An analogy

If CAN is a village phone line, automotive Ethernet is a motorway network with interchanges (switches) and express lanes (TSN) for urgent traffic.

Why Ethernet in cars

Bandwidth (cameras, lidar, displays, OTA), scalability (switches), IP-based software reuse, and lighter cabling using single unshielded twisted pairs (BroadR-Reach → 100BASE-T1; 1000BASE-T1; 2.5–10GBASE-T1; 10BASE-T1S multidrop for low cost).

Network structure

Point-to-point links connect ECUs to switches in zonal controllers and a central gateway/HPC. VLANs separate traffic domains; QoS priorities (802.1p) favour control traffic.

Protocols

SOME/IP: service-oriented communication (method calls, events, service discovery) used in AUTOSAR Adaptive. DoIP: diagnostics and ECU flashing over Ethernet — far faster than CAN. AVB/TSN streams for audio/video. MACsec/IPsec/TLS for security.

Time-Sensitive Networking

TSN standards add determinism: time synchronisation (802.1AS/gPTP), scheduled traffic (802.1Qbv time-aware shaper), frame pre-emption (802.1Qbu), redundancy (802.1CB). This lets safety-relevant control data share links with bulk video.

Formulas

• Raw camera data rate: BW = width × height × fps × bits per pixel
• Link utilisation: U = Σ stream rates / link rate
• Frame efficiency: η = payload / (payload + ≈ 42 bytes overhead incl. preamble/IFG)
• Serialisation delay: t = frame bits / link rate

Worked example: Camera bandwidth

Given: 1920 × 1080, 30 fps, 12 bits/pixel (raw)

Find: Data rate.

• 1920 × 1080 × 30 × 12 = 746 Mbit/s

Answer: ≈ 746 Mbit/s — fits 1000BASE-T1 raw only barely; typically compressed or sent via SerDes

Worked example: Flashing time: CAN vs DoIP

Given: 4 MB software image; CAN effective ≈ 250 kbit/s; DoIP on 100 Mbit/s effective ≈ 50 Mbit/s

Find: Transfer times.

• CAN: 32 Mbit/0.25 Mbit/s = 128 s
• DoIP: 32/50 = 0.64 s (plus erase/verify)

Answer: ≈ 2 min vs < 1 s transfer

Common mistakes

• Wrong: Mixing safety control traffic with video without QoS/TSN. — Right: Use priorities, VLANs and scheduled traffic for determinism.
• Wrong: Ignoring security on IP networks. — Right: Segment networks, use firewalls in gateways, MACsec/TLS, intrusion detection.

Applications

• ADAS & autonomy: Camera, radar and lidar data to central compute.
• Backbone & zonal: Gigabit links between zonal controllers and HPC.
• Diagnostics & OTA: DoIP for fast flashing; OTA updates via connectivity unit.

Key takeaways

• Single-pair Ethernet: 10M to 10G.
• Switches, VLANs, QoS; TSN for determinism.
• SOME/IP services and DoIP diagnostics.
• Backbone of zonal, software-defined vehicles.

Going further

• 10BASE-T1S: Multidrop Ethernet to replace CAN at the edge with IP end-to-end.
• gPTP time sync: Sub-microsecond clock alignment for sensor fusion timestamps.
• Automotive SerDes: Point-to-point multi-gigabit links for raw camera/display streams.