Under the Hood: The Alphabet Soup of Car Connectivity
The automotive industry’s introduction of the Controller Area Network (CAN) protocol in 1986 marked a significant departure from point-to-point wiring for electrical connections, which until then had been the mainstay of the industry. The shift to a relatively lightweight bus-based architecture was a nod to reality: electrical content in the vehicle was scaling fast, and alternatives to one-off wiring were needed.
The first vehicle to use the CAN bus was a Mercedes-Benz S-Class in 1991. CAN connected five Electronic Control Units (ECUs) for engine, body, and climate control. That moment marked the starting point for the evolution—if not revolution—of connectivity standards in the automobile, and it set the stage for architectural disruption.
Today’s Software-Defined Vehicle (SDV) is embracing a zonal architecture, a connectivity scheme based primarily on physical location rather than the specific capability of any given actuator or sensor. This approach typically uses about 300 meters of wiring, a reduction of roughly 4,700 meters compared with earlier distributed designs—a substantial savings in both weight and cost. The zonal model leans on a myriad of connectivity technologies that deliver more robustness, reliability, and deterministic timing than prior schemes. Those improvements are essential as electronic subsystems take over greater—sometimes complete—control of the vehicle.
A useful analogy: connectivity in a car is the nervous system. It must be responsive and provide failover. The nervous system not only links the senses but also controls muscles in response to the brain. Vehicles aren’t any different.
Since CAN, many other connectivity types have been introduced to address different functions in the vehicle. Some, like Ethernet, were adapted from mainstream computing and retrofitted to automotive. Those adaptations generally address real-time, deterministic responsiveness and fault detection. Interestingly, with the possible exception of CAN, standards defined specifically for automotive haven’t found broad adoption elsewhere.
A brief aside on EMI: a wire is, electrically, an antenna. That simple model explains a lot. Both radiated energy limits and required immunity are governed by industry standards. If not managed properly, high-speed signals across long wires can create (and suffer from) EMI. Unfortunately, the need for high-performance communications is at odds with minimizing emissions. In automotive, nothing about this is easy—we just tend to take it for granted.
What follows is a quick survey of the alphabet soup now in play.
Body domain / general-purpose connectivity
These standards are either still in use or have been replaced by newer alternatives:
- CAN (Controller Area Network): used for powertrain, airbags, ABS, and battery management. It has survived because it’s simple and low cost. Historically limited to about 1 Mbit/s.
- CAN-FD (Flexible Data-Rate): a faster derivative of CAN (up to ~8 Mbit/s) that eases CAN’s rate limitations while staying cheaper than Ethernet.
- LIN (Local Interconnect Network): very low-rate communications (~19 kbit/s) used in body control and anywhere cost is more important than performance.
- FlexRay: 10 Mbit/s with deterministic timing and fault protection; optimized for drive-by-wire steering. Over time, it has largely been replaced by automotive-optimized Ethernet.
Two primary technologies have dominated here:
- MOST (Media-Oriented Systems Transport): largely defunct now. It targeted premium in-vehicle entertainment using optical links—great EMI immunity, but high cost and connector reliability issues. Max rate around 150 Mbit/s proved too slow for today’s 4K dash cams.
- LVDS / FPD-Link (Flat Panel Display Link): low-voltage differential signaling with framing for displays. Low swing and differential pairs reduce emissions, and differential reception boosts noise immunity. Still a workhorse for displays and cameras.
A Special Mention: A2B
A2B (Automotive Audio Bus), introduced by Analog Devices in 2014, uses low-cost unshielded twisted pair to carry audio from a head unit (master) to slave devices like speakers and microphones. It supports multiple channels of high-resolution digital audio and microphone arrays for hands-free calling and adaptive noise cancellation.
High-Resolution Sensors and Displays (SerDes family)
For lidar, cameras, high-resolution surround view, and driver information displays, SerDes links embed clocking within the data stream to achieve high rates with low latency:
- GMSL (Gigabit Multimedia Serial Link), FPD-Link, and ASA Motion Link (Automotive SerDes Alliance) support data rates into the multi-gigabit range (commonly up to the mid-teens of Gbit/s) with relatively low latency.
- MIPI (Mobile Industry Peripheral Interface): originally for smartphones (camera and display), now widely adopted in automotive, with extensions for functional safety and security essential to mission-critical use.
Automotive Ethernet (and Switching)
There are multiple (about seven) automotive Ethernet derivatives tuned for a wide spectrum of in-vehicle needs, from 10 Mbit/s to 25 Gbit/s, with different reaches and price points. They address everything from “CAN-plus” body functions to ECU-to-ECU backbones. All use differential signaling; most ride over unshielded single twisted pair to minimize cost and weight. Alongside PHYs, the associated switching fabric has also been adapted for automotive.
Time-Sensitive Networking (TSN)
Standard Ethernet is best-effort. TSN Ethernet adds determinism: end-to-end camera-to-actuator latency under 5 milliseconds with less than 50 microseconds of jitter is achievable. That performance and the ability to prioritize time-critical traffic make Ethernet viable for emergency braking. TSN is a family of specifications; several variants address time sync, scheduling, stream reservation, and reliability.
Wireless in and Around the Vehicle
- Bluetooth: audio and phone-based keys.
- Wi-Fi: over-the-air updates and rear-seat mirroring.
- C-V2X: vehicle-to-vehicle and vehicle-to-infrastructure communications. While multiple variants have been floated over the years, C-V2X is emerging as the superset.
Key Takeaways
Point-to-point wiring is mostly a thing of the past.
Weight and cost pressures drove alternatives; zonal architectures dramatically trim both.
CAN signaled the first big inflection; many link types now coexist, each optimized for its job.
- In automotive, cost always matters; lower-cost solutions win when their features suffice.
- Connectivity is the nervous system—reliability, robustness, latency, and determinism matter more as electronics take control.
- Proven standards keep adapting: TSN Ethernet is becoming a mainstay, and MIPI’s smartphone heritage now carries automotive-grade safety and security.
The automotive industry’s introduction of the Controller Area Network (CAN) protocol in 1986 marked a significant departure from point-to-point wiring for electrical connections, which until then had been the mainstay of the industry. The shift to a relatively lightweight bus-based architecture was a nod to reality: electrical content in the vehicle was scaling fast, and alternatives to one-off wiring were needed.
The first vehicle to use the CAN bus was a Mercedes-Benz S-Class in 1991. CAN connected five Electronic Control Units (ECUs) for engine, body, and climate control. That moment marked the starting point for the evolution—if not revolution—of connectivity standards in the automobile, and it set the stage for architectural disruption.
Today’s Software-Defined Vehicle (SDV) is embracing a zonal architecture, a connectivity scheme based primarily on physical location rather than the specific capability of any given actuator or sensor. This approach typically uses about 300 meters of wiring, a reduction of roughly 4,700 meters compared with earlier distributed designs—a substantial savings in both weight and cost. The zonal model leans on a myriad of connectivity technologies that deliver more robustness, reliability, and deterministic timing than prior schemes. Those improvements are essential as electronic subsystems take over greater—sometimes complete—control of the vehicle.
A useful analogy: connectivity in a car is the nervous system. It must be responsive and provide failover. The nervous system not only links the senses but also controls muscles in response to the brain. Vehicles aren’t any different.
Since CAN, many other connectivity types have been introduced to address different functions in the vehicle. Some, like Ethernet, were adapted from mainstream computing and retrofitted to automotive. Those adaptations generally address real-time, deterministic responsiveness and fault detection. Interestingly, with the possible exception of CAN, standards defined specifically for automotive haven’t found broad adoption elsewhere.
A brief aside on EMI: a wire is, electrically, an antenna. That simple model explains a lot. Both radiated energy limits and required immunity are governed by industry standards. If not managed properly, high-speed signals across long wires can create (and suffer from) EMI. Unfortunately, the need for high-performance communications is at odds with minimizing emissions. In automotive, nothing about this is easy—we just tend to take it for granted.
What follows is a quick survey of the alphabet soup now in play.
Body domain / general-purpose connectivity
These standards are either still in use or have been replaced by newer alternatives:
- CAN (Controller Area Network): used for powertrain, airbags, ABS, and battery management. It has survived because it’s simple and low cost. Historically limited to about 1 Mbit/s.
- CAN-FD (Flexible Data-Rate): a faster derivative of CAN (up to ~8 Mbit/s) that eases CAN’s rate limitations while staying cheaper than Ethernet.
- LIN (Local Interconnect Network): very low-rate communications (~19 kbit/s) used in body control and anywhere cost is more important than performance.
- FlexRay: 10 Mbit/s with deterministic timing and fault protection; optimized for drive-by-wire steering. Over time, it has largely been replaced by automotive-optimized Ethernet.
Two primary technologies have dominated here:
- MOST (Media-Oriented Systems Transport): largely defunct now. It targeted premium in-vehicle entertainment using optical links—great EMI immunity, but high cost and connector reliability issues. Max rate around 150 Mbit/s proved too slow for today’s 4K dash cams.
- LVDS / FPD-Link (Flat Panel Display Link): low-voltage differential signaling with framing for displays. Low swing and differential pairs reduce emissions, and differential reception boosts noise immunity. Still a workhorse for displays and cameras.
A Special Mention: A2B
A2B (Automotive Audio Bus), introduced by Analog Devices in 2014, uses low-cost unshielded twisted pair to carry audio from a head unit (master) to slave devices like speakers and microphones. It supports multiple channels of high-resolution digital audio and microphone arrays for hands-free calling and adaptive noise cancellation.
High-Resolution Sensors and Displays (SerDes family)
For lidar, cameras, high-resolution surround view, and driver information displays, SerDes links embed clocking within the data stream to achieve high rates with low latency:
- GMSL (Gigabit Multimedia Serial Link), FPD-Link, and ASA Motion Link (Automotive SerDes Alliance) support data rates into the multi-gigabit range (commonly up to the mid-teens of Gbit/s) with relatively low latency.
- MIPI (Mobile Industry Peripheral Interface): originally for smartphones (camera and display), now widely adopted in automotive, with extensions for functional safety and security essential to mission-critical use.
Automotive Ethernet (and Switching)
There are multiple (about seven) automotive Ethernet derivatives tuned for a wide spectrum of in-vehicle needs, from 10 Mbit/s to 25 Gbit/s, with different reaches and price points. They address everything from “CAN-plus” body functions to ECU-to-ECU backbones. All use differential signaling; most ride over unshielded single twisted pair to minimize cost and weight. Alongside PHYs, the associated switching fabric has also been adapted for automotive.
Time-Sensitive Networking (TSN)
Standard Ethernet is best-effort. TSN Ethernet adds determinism: end-to-end camera-to-actuator latency under 5 milliseconds with less than 50 microseconds of jitter is achievable. That performance and the ability to prioritize time-critical traffic make Ethernet viable for emergency braking. TSN is a family of specifications; several variants address time sync, scheduling, stream reservation, and reliability.
Wireless in and Around the Vehicle
- Bluetooth: audio and phone-based keys.
- Wi-Fi: over-the-air updates and rear-seat mirroring.
- C-V2X: vehicle-to-vehicle and vehicle-to-infrastructure communications. While multiple variants have been floated over the years, C-V2X is emerging as the superset.
Key Takeaways
Point-to-point wiring is mostly a thing of the past.
Weight and cost pressures drove alternatives; zonal architectures dramatically trim both.
CAN signaled the first big inflection; many link types now coexist, each optimized for its job.
- In automotive, cost always matters; lower-cost solutions win when their features suffice.
- Connectivity is the nervous system—reliability, robustness, latency, and determinism matter more as electronics take control.
- Proven standards keep adapting: TSN Ethernet is becoming a mainstay, and MIPI’s smartphone heritage now carries automotive-grade safety and security.
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