Robust and reliable data transmission protocols are necessary to handle increased data flow and ensure real-time processing.
The evolution of automotive architecture has followed three key stages: distributed architecture, domain-centralized architecture, and emerging zonal architecture. Each stage reflects advancements in functionality, complexity, and efficiency. Distributed architecture, prevalent in early vehicles, relied on numerous function-specific Electronic Control Units (ECUs). While effective for modularity, this setup became untenable as vehicle complexity grew.
Domain-centralized architecture addressed these limitations by introducing domain-specific ECUs that managed functions such as Advanced Driver Assistance Systems (ADAS) or infotainment. These ECUs utilized hybrid communication networks and centralized gateways to enhance data flow and reduce redundancies.
The industry is currently transitioning to zonal architecture, an advanced framework that consolidates functions and simplifies wiring through the introduction of several modular zonal gateways distributed throughout the vehicle. Devices with various functionalities connect to the nearest zonal gateway. Data is centrally processed by a High-Performance Computing Unit (HPCU), while each zonal gateway aggregates data from sensors within its respective zone for processing by the HPCU.
Transitioning to zonal architecture involves significant hurdles for Original Equipment Manufacturers (OEMs) and their partners. One of the primary challenges is the complexity of integrating various systems and ensuring seamless communication between them. The consolidation of functions into specific zones requires robust and reliable data transmission protocols to handle the increased data flow and ensure real-time processing with minimal latency. Furthermore, electric vehicles demand low-power solutions to conserve battery life. While zonal architecture reduces the number of ECUs and simplifies wiring, further reduction in wiring helps lower the vehicle’s overall weight, which can be significant as wiring can range from 1 to 3% of the overall vehicle weight. This reduction in weight enhances battery range and overall efficiency.
The Mobile Industry Processor Interface (MIPI) has introduced several new features that address these challenges. One of the key improvements in the Camera Serial Interface 2 (CSI-2) protocol is the Always-On Sentinel Conduit (AOSC), which enables always-on vision systems with low-power sensors that only wake higher-power ECUs when significant events occur. This feature ensures efficient power management and reduces the overall power consumption of the system.
Another significant feature in CSI-2 is Multi-Pixel Compression (MPC), which provides optimized pixel compression for high-resolution multi-pixel color filter arrays. This feature enhances the quality of image data while reducing the bandwidth required for transmission, ensuring efficient data handling and real-time processing.
The RAW-28 color-depth pixel encoding in CSI-2 supports higher image quality and signal-to-noise ratio in high-dynamic-range image sensors, making it ideal for safety-critical applications in automotive systems.
Additionally, the Smart Region of Interest (SROI) feature in CSI-2 enables more efficient image analysis using AI-based vision inference algorithms, further enhancing the capabilities of ADAS and other advanced automotive systems.
Electromagnetic interference (EMI) is a significant concern in automotive systems due to the high density of electronic components and the need for reliable data transmission in safety-critical applications. The embedded clock feature in the MIPI D-PHY v3.5 specification significantly reduces EMI by minimizing the number of wires required for data transmission. By freeing up a lane of traffic that would otherwise carry the forwarded-clock signal, the embedded clock mode boosts the effective throughput of a D-PHY link between an application processor and a megapixel camera, a high-resolution display, or other sensors.
Unified Serial Link (USL) encapsulated transport in CSI-2 provides a high-bandwidth, low-latency communication link that reduces the number of wires required for data transmission. This not only simplifies the wiring harness but also enhances the reliability and efficiency of data transmission. USL also includes replay protection and encapsulation, ensuring data integrity and security.
Latency Reduction and Transport Efficiency (LTRE) in CSI-2 addresses the need for real-time data processing in automotive systems. By reducing overhead and increasing the number of sensors that could be aggregated, LTRE ensures that data is transmitted and processed with minimal latency. This is essential for applications such as ADAS, where real-time data processing is critical for safety and performance.
MIPI CSI-2 is designed to be compatible with both short-reach and long-reach solutions. The MIPI A-PHY v2.0 specification supports up to 32 Gbps downlink and 1600 Mbps uplink data rates, providing robust and reliable data transmission over long distances. Short reach solutions leverage MIPI D-PHY and C-PHY, whereas long reach solutions can be realized using MIPI A-PHY and non-MIPI SerDes bridges like ASA Motion Link. The CSI-2 protocol can be “tunneled” over non-MIPI SerDes bridges using a CSI-2 Application Stream Encapsulation Protocol (ASEP) developed and maintained by ASA. This ensures seamless integration with various long-reach solutions and enhances the flexibility of the overall system architecture.
The transition from distributed to zonal architecture in the automotive industry is a significant step towards realizing the full potential of software-defined vehicles. While this shift presents several challenges, the new features in MIPI CSI-2, in conjunction with DSI-2 and A-PHY, offer robust solutions to address these challenges. By ensuring compatibility and flexibility with other long-reach solutions, MIPI CSI-2 plays a crucial role in shaping the future of automotive technology, enabling more efficient, scalable, and advanced vehicle systems. Over the years, MIPI has continuously adapted to address the requirements of the automotive industry, incorporating new features and ensuring its relevance in the rapidly evolving automotive sector.
Since 2010, Rambus has been a leading provider of MIPI IP solutions, offering 32 and 64-bit digital controllers for MIPI CSI-2 and MIPI DSI-2. Collaborating with top-tier MIPI C/D-PHY suppliers, Rambus solutions have supported prominent leaders in the automotive industry with over 250 ASIC and FPGA MIPI designs. If you are working on zonal architecture systems, we offer expert technical support, a comprehensive suite of customization and integration services, an applicable safety manual, FMEDA, and DFMEA. As the MIPI standard advances, Rambus remains committed to enabling the latest capabilities in your designs.
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