ChatGPT has detonated the demand for digital chips with large computing power integrated with storage and computing. The reason why ChatGPT can exist is largely due to the support of digital technology. Digital technology is one of the greatest inventions in human history, including coding, compression, transmission, modulation and demodulation and other technologies.
Today, digital technology has become the five major technology systems covering big data, cloud computing, Internet of Things, blockchain, and artificial intelligence. However, in the so-called most advanced intelligent networked vehicles, the transmission of vehicle data is still using the analog signal transmission method of the fuel vehicle era. Now, this situation is changing.
Analog vs. Digital Transmission Tradeoffs
Although analog transmission does not need to consider the content of transmission, it has the advantages of extremely high resolution under ideal conditions, intuitive and easy to implement, simple processing method, and no quantization error, which can accurately describe physical quantities, but its fatal disadvantages are:
1. The signal amplitude changes continuously and is relatively weak, and it will attenuate after a certain distance. So the transmission distance is short, and a power amplifier is required for longer distances;
2. The anti-interference ability is weak. It is easy to be interfered by various superimposed noises in the transmission process, and it is difficult to eliminate. The signal confidentiality is poor, and the communication is easy to be eavesdropped.
The advantages of digital transmission are firstly data integrity. The transmission signal amplitude is discrete, and the binary signal has only two values. The receiving end only needs to distinguish two states. As long as the noise is not large enough to affect the correct judgment, it can be correctly received.
Secondly, the anti-interference ability is strong, and the digital signal can be transmitted to a certain distance before ensuring that the attenuation does not endanger the data integrity. In order to be able to reach a longer transmission distance, a transponder can be used.
The third is the effective use of bandwidth, and the digitally encoded signals are safe and confidential.
Therefore, in view of the advantages of digital transmission, it is generally believed in the field of communication that it is better to use digital transmission. In a car, some physical quantities obtained by sensors and cameras, such as speed, temperature, pressure, etc., are analog signals, which need to be converted into digital signals and sent to the computer for calculation and processing. Then the processing results are converted into ECU (Electronic Control Unit) Analog signal to drive the actuator.
Current state of automotive data transmission
Now, the automotive industry is shifting from private protocols to open standards. Some OEMs have realized that data transmission is the bottleneck of in-vehicle communication for intelligent networked vehicles. They hope to use digital signals and open standards to replace the previously used private protocols.
The so-called proprietary protocol refers to non-open standards customized by some semiconductor manufacturers based on their proprietary technologies. The SerDes currently used in automotive applications is such a proprietary solution, which means that if not all components are from the same chip supplier, components between manufacturers cannot be used together.
Ser and Des in SerDes represent serializer (Serializer) and deserializer (Deserializer) respectively, and its main function is to convert low-speed parallel signals into high-speed low-voltage differential signals (LVDS) and send and receive them through serial links.
The early SerDes technology was applied to long-distance WAN communication based on optical fiber media. With the continuous improvement of data transmission rate, this technology has been expanded to other application fields. Due to the high-speed transmission characteristics of SerDes, the automotive field has also adopted it as a choice for high-speed connections in recent years.
A- PHY for cars
So, what is the difference between the MIPI A-PHY standard and traditional SerDes? Will it coexist in automotive applications in the future? Recently, Gideon Kedem, senior vice president and head of automotive business at Valens, said: “The biggest difference between the two is that MIPI A-PHY is a global open standard. Chip suppliers can design, develop and produce corresponding MIPI A-PHY according to this standard.”
In other words, since there are no patent restrictions, any chip manufacturer with technical capabilities can develop and manufacture chips that meet the MIPI A-PHY standard.
In fact, A-PHY is like the Ethernet standard, which helps to establish a better and more standardized ecosystem in the industry, so many chip players are developing and producing chips that meet the A-PHY protocol.
In the future, there will be more and more A-PHY chip manufacturers at home and abroad, but different chip manufacturers have different research and development capabilities, and the products they make will have some differences in performance or cost performance
Future Plan of OEMs
In the automotive industry, GMSL or FPD-Link are proprietary protocols for analog signal transmission, while MIPI A-PHY has more advantage: it supports ultra-high bandwidth, zero delay and excellent EMC performance, which can ensure the safety of the car High-speed connectivity for time-sensitive and time-sensitive applications; meeting the constraints of automotive architecture to reduce space, weight, and complexity requirements.
The MIPI A-PHY next-generation chipset for vehicle safety connectivity uses unshielded twisted pair cables and simple connectors to plug and play, which can greatly reduce the total system cost and provide car manufacturers with an efficient solution.
Chips based on digital design can increase the transmission rate proportionally, and can also use a unique mechanism to deal with EMI problems, so as to meet the severe challenges of electromagnetic interference that are becoming more and more obvious in the development of intelligent, networked, and electrified vehicles.
Now, more and more OEMs hope to use open standards instead of proprietary protocols, not to mention that digital transmission has greater advantages than analog transmission. As for how to choose between OEMs, Tier 1 and Tier 2, you still need to weigh the pros and cons and choose the connection solution that best suits your situation.
