In the Blind Spot Detection (BSD) system, the high-speed data transmission line in the vehicle needs to transmit real-time obstacle information collected by radar, cameras, or ultrasonic sensors on the side and rear of the vehicle to ensure that the system quickly identifies potential collision risks and triggers warnings or automatic interventions. The following is a high-speed data transmission solution for blind spot detection applications:
1. Core requirements for blind spot detection system
Real time performance: Upon detecting an obstacle, a warning (such as a rearview mirror prompt or steering wheel vibration) must be triggered within 50ms.
Medium bandwidth: The data volume of single-sided radar or camera is about 100-500Mbps (such as 24GHz/77GHz radar or 720p camera).
Anti interference capability: The vehicle is located near the tires and motor on the rear side, with strong electromagnetic interference (EMI).
Environmental adaptability: Resistant to rain, mud, and vibration (especially in areas with frequent door opening and closing).
Low power consumption: Avoid overheating of the wiring harness and affecting the lifespan of the sensor.
2. Sensor type and transmission technology adaptation
(1)Millimeter wave radar (77GHz/79GHz)
Data characteristics: target distance, speed, azimuth information (approximately 50-100Mbps).
Transmission scheme:
Coaxial cable (FAKRA/HSD): Traditional solution, supports up to 6Gbps, suitable for short-range radar signal transmission.
Vehicle Ethernet (100BASE-T1): Convert radar raw data into Ethernet protocol through SerDes chip, supporting longer distance (15m+) and anti-interference.
(2) Ultrasonic sensor
Data characteristics: Low bandwidth (<10Mbps), but high real-time performance (<10ms latency) is required.
Transmission scheme:
CAN FD： Low cost, supporting multi-sensor shared bus to meet low bandwidth requirements.
LVDS (Low Voltage Differential Signaling): point-to-point transmission ensures low latency, but requires additional shielding.
(3) Side view camera
Data characteristics: 720p/1080p video stream (200-800Mbps).
Transmission scheme:
MIPI CSI-2 to Ethernet: The camera outputs through MIPI and converts it to 1000BASE-T1 Ethernet through a protocol conversion chip (such as TI DS90UB9xx).
Coaxial cable (HSD connector): directly transmits raw video signals (requires adding repeaters to extend transmission distance).
3. Design of dedicated transmission scheme for blind spot detection
(1) Hybrid transmission architecture
Sensor end:
Millimeter wave radar uses coaxial cable and Ethernet conversion module to balance anti-interference and scalability.
The side view camera uses MIPI to Ethernet bridge chips (such as Maxim MAX96712) and supports 15m transmission.
Central processing end:
Ethernet switches (such as the Marvel 88Q5050) integrate multiple sensor data and ensure priority transmission through TSN (Time Sensitive Network).
(2) Redundancy and Fault Tolerance Mechanism
Dual link backup: Critical radar data is transmitted in parallel through dual cables (Ethernet+coaxial), and automatically switches in case of any link failure.
Data verification: CRC (cyclic redundancy check) and retransmission protocol (such as AVTP retransmission) are used to prevent misjudgment caused by data loss.
(3) Anti interference design
Shielding optimization:
Coaxial cables use double-layer shielding (aluminum foil+braided layer), and connectors use FAKRA Mini (360 ° shielding).
The Ethernet cable adopts AWG24 twisted pair and metal braided layer, meeting the CISPR 25 Class 5 standard.
Power isolation: Separate the sensor power line from the data line to avoid common mode noise coupling.
(4) Lightweight and Wiring Optimization
Regional cabling: Connect blind spot detection sensors to the nearest regional gateway (Zonal Gateway) to reduce the length of the wiring harness (typically<5m).
Composite cable: integrates power and data cables (such as coaxial power supply PoC), reducing the number of connectors.
4. Typical application cases
Case 1: Radar+Camera Fusion Solution Based on Ethernet
Sensor: 77GHz radar+side view 1080p camera.
Transmission link:
Radar data → 100BASE-T1 Ethernet → Regional gateway.
Camera data → MIPI CSI-2 → GMSL converter → 1000BASE-T1 Ethernet → Regional gateway.
Advantages: Unified Ethernet protocol simplifies data processing and supports future upgrades to multi-sensor fusion.
Case 2: Low cost Ultrasonic BSD System
Sensor: 12 channel ultrasonic probe.
Transmission link: Ultrasonic signal → LVDS → CAN FD → Central ECU.
Advantage: Utilizing existing CAN networks to reduce costs, suitable for economical vehicle models.
5. Key points of testing and verification
Real time testing: Simulate the scene of obstacles appearing and verify the end-to-end delay (less than 100ms) from sensor detection to system response.
EMC testing:
Test the false alarm rate during motor start-up and wiper operation.
Verify 10V/m radiation immunity (ISO 11452-2).
Mechanical reliability testing:
Check the contact resistance of the connector after opening and closing the car door 100000 times.
The performance stability of the wiring harness under temperature cycling from -40 ° C to 85 ° C.
6. Future Trends
5G millimeter wave feedback: Share blind spot data with other vehicles (V2V) through in vehicle 5G modules to expand detection range.
AI edge processing: Integrating AI chips (such as NVIDIA Jetson Nano) at the sensor end, only transmitting structured data (such as obstacle coordinates), reducing bandwidth requirements.
Plastic optical fiber (POF): replaces copper cables and solves the problem of cable fatigue caused by repeated bending in the side door area.
The high-speed data transmission of blind spot detection system needs to be designed around three core requirements: real-time performance, anti-interference, and lightweight
Prioritize the use of onboard Ethernet (100/1000BASE-T1) to achieve sensor fusion and long-distance transmission.
Traditional coaxial cables and CAN FD are still suitable for low-cost or single sensor scenarios.
In the future, network efficiency can be further optimized through regional architecture and TSN, while exploring the possibility of hybrid wireless and wired transmission.
When designing, it is necessary to choose the most cost-effective solution based on the vehicle's positioning (luxury/economy) and ADAS functional level (L1/L2+).