Centralized architecture meets automotive computing demand
Centralized architecture refers to in-vehicle network (IVN) designs that have Ethernet occupying a dominant position within the central node, and is an automotive network format that has become mainstream among smart vehicles. The greater levels of data transmission capacity and computing power demanded by autonomous vehicles means that traditional distributed architectures can no longer meet scalability and communication performance requirements.
Instead, further integration between multiple domain controllers is expected to dominate the market within the near future, giving rise to domain and cross-domain architectures until true centralized architecture becomes the norm.
But for smart vehicle architecture to reach this new frontier, it will require Automotive Ethernet networks including Time Sensitive Networks (TSN) to be superimposed upon existing architecture. This will ensure that low latency and time synchronization can be realized to enable real-time computing and high-speed data transmission. Let’s take a closer look at the components of distributed and centralized architecture to understand how future automotives will be designed.
The evolution from distributed to centralized architecture
1. Distributed architecture
Each function corresponds to a specific hardware responsible for perception, decision, and execution. This leads to more wire harness and complex topologies, creating redundancies within internal communication channels that wastes computing power unnecessarily.
2. Domain architecture
The architecture changes from a decentralized, distributed architecture to regional concentration with fewer nodes and simpler over-the-air (OTA) upgrades. Each domain is equipped with a controller with higher computing power and wider range, reducing the number of Electronic Control Units (ECUs), creating higher computer power, and more flexible network communications.
3. Cross-domain architecture
Further integration between domain controllers is enforced through cross-domain control architecture. This further centralizes electronic control within an automotive system, improving performance and reducing cost across security, power, and cross-domain execution.
4. Centralized architecture
True central computing architecture consists of a central computing unit, cloud computing, sensors, actuators, and information that is calculated by the central computing unit. By optimizing processing, the demand for computer power can be reduced while still allowing information to be processed quickly enough to achieve low latency.
The history of Bus technologies and what’s next with automotive networks
CAN, LIN, and FlexRay in-vehicle networks
Bus technologies currently deployed within in-vehicle networks include CAN, LIN, FlexRay, MOST, LVDS, and vehicle Ethernet. CAN buses supplemented by LIN bus cover the majority of the market, with CAN being the most widely used standard protocol for transmitting data within active vehicle networks. On the other hand, LIN is a low-cost, universal serial bus that provides CAN with auxiliary functions within doors, sunroofs, seat controls, and more.
However, FlexRay is quickly gaining prominence as the next generation of automotive control bus technology after CAN and LIN. With its higher bandwidth, FlexRay has been successfully applied to wire control systems within mid-to-high end cars. Unfortunately, because FlexRay can only be developed by a single manufacturer at the time of writing, development costs are high. Both FlexRay and MOST are prime candidates for in-vehicle multimedia data transmission, but likely have to be incorporated into a standard organization if mass distribution is to be achieved.
The Automotive Ethernet advantage
With more automobile electronics flooding the market than ever before, the number of ECUs within a single vehicle has increased significantly from an average of 20 to 30 to more than 100, with the length of some vehicle wiring harnesses reaching up to 2.5 miles. Under these circumstances, the limitations of CAN bus become apparent. Because it can only achieve half-duplex communication and low transmission speeds, CAN bus is not quite suitable for high-speed, real-time, two-way data pathways required by modern automotive networks.
Automotive Ethernet is expected to become a key technology among automotive networks thanks to its high bandwidth, lightweight wiring harness, and high cost effectiveness. Unlike traditional automotive networks, Ethernet provides data transmission capabilities that are high enough to meet bandwidth-intensive applications. Other technical advantages that it provides include high automotive reliability, appropriate bandwidth allocation, as well as low electromagnetic radiation, power consumption, latency, and hardware weight.
An overview of automotive Ethernet hardware and software
Hardware structure of automotive Ethernet
Automotive Ethernet primarily operates on a pair of copper twisted transmission channels, which have good mechanical strength, small bending radius, and good resistance to harsh weather conditions. They also can be used directly without photoelectric conversion equipment, making them the ideal choice for “last hundred” data transmission. According to the Ethernet Alliance, the current transmission rate of copper-based Ethernet lies between 10Mb/s and 10Gb/s, a level that is expected to rise as new Ethernet designs surface.
Mainstream Ethernet standards of today
Already, Ethernet has replaced numerous networks to become the most commonly used LAN technology in the world. Over 50 years of development, Ethernet speed has increased from the standard Ethernet (10Mbps) to fast Ethernet (100Mbps) to the current Gigabit Ethernet (1Gbps). In recent years, new rate standards such as 2.5GE, 5GE, 25GE, and 50GE have also surfaced to accommodate various application scenarios and cost factors. Gigabit Ethernet 1000BASE-T is the current mainstream Ethernet based twisted pair technology, which is itself based on the 802.3ab standard and can transmit 1000Mb/s data streams on Category 5 twisted pairs exceeding 100M.
How Ethernet is expected to evolve
As the communication solution with the fastest transmission rate among all types of buses, Ethernet application is expected to expand from localized applications such as smart cockpits to eventually become the backbone of in-vehicle communication. This development is expected to occur in three stages:
- Promotion and application of DoIP (Diagnostics Over Internet Protocol): This will enable on-board diagnostic systems and ECU software refresh as well as driving assistance systems that use IP cameras.
- Integration of subsystems: Combining applications such as multimedia, driving assistance, and diagnostic interfaces.
- Ethernet as an IVN backbone: At this stage, TSN will be gradually introduced and the cross-domain automotive network will be formed.
Drive into the future of automotive ethernet with industry experts
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