In the field of Driver Assistance Systems (ADAS) and autonomous driving technology, high-speed data transmission lines in vehicles play a crucial role, responsible for real-time transmission of large amounts of data from cameras, radar, LiDAR, ultrasonic sensors, and other sources. These data need to be quickly and reliably transmitted to the central computing unit (ECU) for processing and decision-making. The following are solutions for the application of high-speed data transmission lines in safe driving assistance for vehicles:
1. Core requirements for high-speed data transmission lines
High bandwidth: ADAS sensors (such as high-definition cameras and LiDAR) generate several gigabytes of data per second, requiring support for gigabit (Gbps) or even higher transmission rates.
Low latency: High real-time requirements (millisecond level latency) ensure that the system responds quickly to emergency scenarios (such as automatic emergency braking).
Anti interference: The electromagnetic interference (EMI) in the vehicle environment is complex, requiring shielding design and high reliability.
Durability: Suitable for harsh environments such as wide temperature range (-40 ° C to 125 ° C), vibration, and humidity.
Lightweight and miniaturized: reduce the volume and weight of wiring harnesses, adapt to compact car layouts.
2. Mainstream high-speed data transmission technology
(1) Automotive EthernetStandard: Supports 100BASE-T1 (100Mbps), 1000BASE-T1 (1Gbps), 10GBASE-T1 (10Gbps), etc.
Advantages: High bandwidth, low latency, single pair twisted pair design (saving harness weight), supporting time sensitive network (TSN) for deterministic transmission.
Application: Connection from sensors to domain controllers (DCUs) and from domain controllers to central computing platforms (HPC).
(2) Coaxial CableFAKRA/HSD connector: traditionally used for cameras and radars, supports high-speed signals (such as LVDS), but has lower bandwidth (typically<6Gbps).
Upgrade plan: Adopt Coaxial Shielded Twisted Pair (Coaxial STP) to enhance anti-interference capability. (3) MIPI protocol (Camera Serial Interface, CSI-2)
Features: Designed specifically for cameras, supporting high-resolution image transmission (such as 8MP cameras).
Challenge: Short transmission distance (usually<15cm), requiring protocol converters (such as MIPI to LVDS/Ethernet) to extend the transmission distance.
(3) MIPI protocol (Camera Serial Interface, CSI-2)
Features: Designed specifically for cameras, supporting high-resolution image transmission (such as 8MP cameras).
Challenge: Short transmission distance (usually<15cm), requiring protocol converters (such as MIPI to LVDS/Ethernet) to extend the transmission distance.
(4) PCIe（Peripheral Component Interconnect Express）
Application: Used for high-speed interconnection between domain controllers and central computing platforms (such as NVIDIA DRIVE platform), supporting multi-channel configuration (x4/x8), with a bandwidth of up to 16GT/s.
(5) Optical Fiber
Advantages: Ultra high bandwidth (up to 25Gbps+), anti electromagnetic interference, lightweight.
Challenge: High cost, need to solve the reliability and vibration resistance issues of fiber optic connectors.
Application: Lidar data, high-resolution surround view system.
3. Solution design for safe driving assistance system
(1) Hierarchical network architecture
Sensor layer: Use MIPI CSI-2 (camera) or LVDS (radar) for short-range transmission.
Domain controller layer: Integrate multi-sensor data through onboard Ethernet or PCIe.
Central computing layer: Multiple domain controllers are connected using high-speed Ethernet (10Gbps+) or PCIe.(2) Redundant and fault-tolerant design
Dual channel redundancy: Key sensors (such as brake system cameras) are equipped with dual cables to ensure that the system can still operate in the event of a single point of failure.
Ring topology: Ethernet TSN supports ring networks to enhance reliability.
(3) EMC (Electromagnetic Compatibility) protection
Shielding design: Twisted pair cable+aluminum foil/braided layer shielding, connector adopts 360 ° fully shielded interface (such as H-MTD).
Common mode filtering: Deploy common mode choke coils (CMC) at both ends of the transmission line to suppress high-frequency noise.
(4) Lightweight and integrated design
Multi protocol fusion: Integrating Ethernet, CAN FD, FlexRay and other protocols through switches to reduce the number of wiring harnesses.
Zonal Architecture: Distribute wiring harnesses according to vehicle areas to shorten transmission distances.
4. Typical application scenarios
Automatic Emergency Braking (AEB): Radar and camera data are transmitted in real-time to the ECU via Ethernet.
Lane Keeping Assist (LKA): High definition camera images are transmitted via MIPI to Ethernet.
Surround view system: 4-8 camera data are aggregated through LVDS or Ethernet.
Lidar point cloud transmission: Fiber optic or high-speed Ethernet (10Gbps+) supports millions of point cloud data per second.
5. Testing and Verification
Signal integrity testing: Use eye diagram analysis and TDR (Time Domain Reflectometer) to ensure high-speed signal quality.
Environmental testing: vibration, temperature cycling, salt spray testing (ISO 16750 standard).
EMC testing: Verify CISPR 25 Class 5 anti-interference capability.
6. Future Trends
Multi gigabit Ethernet: evolving towards 10Gbps+, supporting L4/L5 autonomous driving.
Wireless transmission supplement: 5G V2X collaborates with wired transmission to reduce the complexity of wiring harnesses.
Silicon photonics technology: a low-cost fiber optic solution that breaks through bandwidth bottlenecks.
The on-board high-speed data transmission line is the "nervous system" of ADAS and auto drive system, and bandwidth, delay, reliability and cost should be comprehensively considered. In the future, as the number and resolution of sensors increase, Ethernet and fiber optic will become mainstream, while standardization (such as IEEE 802.3ch) and intelligence (TSN) will drive further technological maturity. When designing, it is necessary to select the optimal transmission protocol and topology structure based on the specific ADAS functional requirements of the vehicle model.