Bandwidth is the key: A brief analysis of the application of networks in automobiles

Just like today's smartphones, cars are no longer a simple means of transportation. The use of new technologies has made driving safer, and the continuous enrichment of in-vehicle entertainment systems has also improved the quality of car use. With the increase of in-vehicle electronic devices, traditional simple circuits can no longer meet the demand for data transmission speed, so the expansion of in-vehicle networks has been carried out, among which bandwidth is a link that has been vigorously developed. It can be said that without sufficient bandwidth support, any idea is empty talk.

Why do we need more bandwidth?

We are all familiar with bandwidth. Just like home networks, it is used to measure the ability to transmit data at high speeds. The same is true in cars. A high-speed in-vehicle network environment is like a multi-lane bridge between various sensors and processors. Combined with the performance of the processor, it ensures that related functions can respond accurately and quickly.

In this regard, some active safety technologies that have not yet been widely popularized are particularly prominent. Many active safety systems with active braking functions identify the road conditions in front of the vehicle through the images provided by the camera behind the central rearview mirror. Unlike traditional radar probes, the data transmission of image information is much larger. If the transmission speed cannot be ensured, when a collision risk is detected, the control computer of the active safety system will not be able to issue a braking command as soon as possible.

Previously, we expected that the autonomous driving technology that will be promoted starting in 2020 will be more dependent on bandwidth. A large amount of information from the actual road is captured by various sensors distributed around the vehicle body and transmitted to the processor for calculation. The instructions are then transmitted to the actuator for action. This requires a larger bandwidth as a guarantee.

What does the current high-speed transmission of data rely on?

The transmission speed of information is also reflected in the in-vehicle entertainment system. At present, most high-end cars rely on the MOST system to form a set of in-vehicle entertainment system architecture. In the MOST system, the transmission of information data relies on optical fibers, and optical fiber lines are used to replace traditional automotive wiring harnesses. It can provide a collective bandwidth of about 25Mbps. In terms of transmission speed, it basically guarantees the needs of existing in-vehicle entertainment systems. In this architecture, equipment such as navigation, audio, and car phones are installed. The Audi MMI we are familiar with adopts this method. However, with the development of in-vehicle interconnection systems, the MOST system that uses optical fiber lines to transmit information may be difficult to support the increasingly large in-vehicle interconnection system in terms of hardware structure and data transmission speed. Not only that, the MOST system does not have the ability to solve the integration of in-vehicle networks.

As a giant in the industry, Broadcom (which has close cooperative relations with Samsung Mobile, Gehua Cable, Bosch, Continental and other companies) has launched a new data transmission technology and applied it to the 2014 BMW X5 model. The new technology has greatly improved the data transmission speed compared with traditional technology. Not only that, the wire harness used is also smaller. Originally, 3 pairs of wire harnesses were required to support a bandwidth of 100Mbps. The data transmission technology launched by Broadcom only needs 1 pair of wire harnesses to support a bandwidth of 100Mbps (in 2016, a technology that can transmit 1Gbps with 1 pair of wires will be launched). Another advantage is that the total data transmission speed will not be greatly attenuated due to the addition of equipment.

In addition, the new technology is more reasonable than the MOST system in terms of structure. Why do you say that? Based on the structural characteristics of the MOST bus, if any component belonging to the MOST bus structure fails during actual car use, the entire entertainment system will be paralyzed. For example, some high-end cars are equipped with car phones, which are built in the MOST structure. When this component fails, the entire MOST bus will be disconnected, which will affect the use of the radio, navigation and other entertainment equipment. Only after the faulty component is repaired can the entire system be used normally. This characteristic of affecting the entire system invisibly increases the probability of failure of the entire system. The data transmission technology launched by Broadcom can avoid similar situations from a structural perspective.

Overall, although the MOST system with optical fiber as the transmission medium has certain advantages in bandwidth and anti-interference ability, its expansion capability has entered a bottleneck stage that is difficult to break through. In contrast, the technology based on the "Ethernet" architecture launched by Broadcom not only has higher transmission speed and more reasonable structure, but they will also use the characteristics of this architecture to promote the integration of vehicle networks. Both wired networks (such as CANBus) and wireless networks based on Bluetooth or Wi-Fi can be integrated in the same network environment, simplifying the structure and helping to improve data transmission speed.

Does the touch experience of the central display screen have to do with bandwidth?

We have always paid more attention to the experience of the smoothness of the control of the central display screen with touch function, but the effect in this regard does not seem to satisfy us, and it is even more unmatched compared with Apple products. In fact, the ability of the processor determines the smoothness of the picture to a certain extent. In addition, the capacitive screen that can support multi-touch function requires the screen to recognize fingers more directly, but unlike ordinary electronic products, the original central control display installed in the car needs to meet the requirements of safety regulations. Therefore, the thickness of the screen will affect the recognition of finger movements, thereby slowing down the rhythm of the entire touch. In this way, compared with the processor, there is no direct relationship between the touch smoothness of the car's central display and the bandwidth.

Editor's summary:

The advancement of automotive technology requires not only a forward-looking concept, but more importantly, how to turn it into reality. The bandwidth problem mentioned in this article may strangle innovation, and the introduction of "Ethernet" is likely to make a qualitative breakthrough in the bandwidth of the vehicle network. At least in the process of investing in new technologies, engineers will not be hesitant in applying technology due to data transmission speed issues. Of course, whether it is new technology or the development of technology to achieve greater bandwidth, they are complementary. The success of new technology must be based on a market-oriented approach. At the same time, as the support behind it, the demand for bandwidth is automatically transformed into a research and development goal.