A-PHY: Pioneering next-generation long-distance module transmission technology, empowering autonomous driving

A-PHY: Pioneering next-generation long-distance module transmission technology, empowering autonomous driving

Preface

A-PHY is the automotive industry's first asymmetric long-distance SerDes physical-layer specification tailored for ADAS/ADS surround-sensor applications and infotainment display systems. Developed to meet the demands of an increasingly complex and high-speed communication environment, it serves as an asymmetric data link in a point-to-point topology, enabling capabilities such as high-speed unidirectional data transmission and embedded bidirectional control data. A-PHY is specifically designed to address the unique needs of the automotive sector.

What advantages does nA-PHY technology offer when applied at the module level? 1 of 311

To enable in-vehicle module applications, Sunny Optical Intelligence and Valens initiated a strategic partnership in 2022, jointly embarking on the R&D of automotive UTP modules. Thanks to the collaborative efforts of both parties, the 3M module has now been developed and is undergoing relevant testing, marking the initial completion of the development work.

The advantages that A-PHY brings to automotive applications can be seen in the following areas:

① Utilize lower channel carrier frequencies to support higher data bandwidths, thereby meeting the high-volume data transmission needs of in-vehicle systems while reducing demands on transmission cables and connectors.

② Addressing issues such as insufficient transmission distance, inadequate bandwidth, and unstable data in vehicular big data applications.

③ A-PHY is a globally recognized open standard that enables devices and interfaces from different manufacturers to achieve mutual compatibility and seamless interoperability, thereby enriching the supply chain resources for automakers and equipment suppliers while mitigating supply chain risks.

④ A-PHY can be directly integrated into both the front-end sensor chips and the back-end SoC chips in the future, ultimately simplifying vehicle system integration, reducing the need for bridging ICs, and effectively lowering overall vehicle system costs.

How does nA-PHY achieve high data rates and low bit-error rates in transmission?

A-PHY's PHY-layer retransmission and narrowband interference canceller jointly achieve this result.

In signal transmission, the retransmission mechanism refers to the phenomenon where data packets are lost during data transfer due to factors such as signal attenuation, noise, or distortion. To ensure data integrity, it is necessary to implement specific measures to retransmit the lost packets. Common retransmission mechanisms include timeout retransmission, fast retransmission, SACK, and D-SACK, among others.

In the A-PHY architecture, time-bounded local PHY-level retransmission is employed at the physical layer. This approach ensures timely transmission of layer signals within a predefined range.

(A-PHY Transmission Architecture)

To combat the impact of various noises from the vehicle environment, Valens has developed a chip specifically for A-PHY that enables dynamic PAM modulation of retransmitted data packets, offering enhanced error resilience.

When sudden, persistent noise occurs in the external environment, the A-PHY chip can perform re-training, enabling the module to effectively counteract the impact of external noise and return to a normal state of information transmission. Meanwhile, the RTS retransmission mechanism ensures that any erroneous data segments can be fully restored.

(On the left is the module without dynamic modulation, and on the right is the module with dynamic modulation.)

Under the combined effect of the above-mentioned features, the A-PHY automotive module delivers exceptionally stable and reliable transmission with an extremely low packet error (or loss) rate (PER < 10^-19)—significantly lower than other existing solutions—effectively ensuring high-speed data transfer (up to 32 Gbps per single channel, with a net data rate of 28.8 Gbps).

How nA-PHY Effectively Reduces Vehicle Wiring Harness Systems

Ideally, the system could achieve the simplest end-to-end communication between the sensor and the ECU. However, given current sensor and display technology solutions, in-vehicle information communication still relies on D-PHY/C-PHY, with protocol conversion and long-distance transmission handled via a bridging chip (using the SerDes architecture). The MIPI A-PHY-based solution, meanwhile, delivers significant cost savings across three key areas:

① MIPI A-PHY SerDes can utilize unshielded twisted pair (UTP) cables and unshielded straight-through connectors when operating at PAM-4 and link speeds of up to 4Gbps. These solutions are smaller, lighter, more cost-effective, and easier to install.

② The camera design and its internal PCB have been optimized to reduce costs. Additionally, using UTP cables has simplified the process of sealing the external connections to the camera module—further lowering expenses.

③ In long-distance transmission scenarios, it can also effectively resist external interference. A-PHY can be directly connected to the ECU, which undoubtedly reduces the number of bridging chips and wiring harnesses within the ECU, thereby lowering costs.

(On the left is the vehicle wiring harness layout using the A-PHY module, while on the right is the layout using a conventional module.)

How nA-PHY technology-enabled modules can empower autonomous driving

Shunyu's intelligent technology, backed by expert design capabilities and a mature manufacturing system, has developed a compact 3M surround-view module measuring 23 x 23 mm—perfectly tailored to tackle the challenge of limited installation space typically reserved on vehicle bodies. The module is equipped with the SONY IMX623 chip and features a 200-degree wide-angle fish-eye lens designed specifically for automotive applications. It utilizes UTP connectors and a Valens chip, enabling long-distance signal transmission while significantly reducing costs. Here are the module specifications:

The module equipped with the A-PHY chip features stable long-distance transmission capability. Even after connecting a 16-meter UTP test harness, the module continued to function properly, successfully displaying images and transmitting signals without any issues. Software tests showed a steady frame rate, with zero error frames detected.

Compared to POC harness modules, UTP harness modules feature a smaller diameter due to the absence of a shielding jacket, allowing for space savings, greater flexibility, and easier installation—making them better suited to automakers' vehicle body assembly requirements.

Moreover, UTP harnesses offer a price advantage over POC harnesses. While this edge isn’t particularly pronounced in the single-module segment, extending the UTP connector solution to downstream components paired with modules—or even entire vehicle systems—could yield significant cost benefits.

Overall, Valens' A-PHY technology is a groundbreaking innovation that not only enhances the efficiency and stability of signal transmission but also delivers a superior user experience, opening up new opportunities for in-vehicle camera module systems. We believe that as A-PHY technology continues to evolve and mature, its future applications will shine even brighter.

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