With the automotive industry entering the Internet era, both new and old forces in the automotive industry focus on ADAS research, and the emerging forces represented by Tesla are in the front. However, the recent Tesla auto-driving accident seems to indicate that millimeter-wave radar plus camera, an autonomous environmental awareness system, is a congenital defect and cannot accurately perceive all-weather and all-weather road conditions, while collaborative environmental awareness systems can complement it well. The foundation of collaborative environmental awareness system is the V2X technology of vehicle networking.

What is V2X

V2X (Vehicle-To-Everything), as its name implies, means that the vehicle is 100% connected with the outside world, which is the foundation and key technology of the future smart car, auto-driving, smart transportation system.

V2X consists of four parts:

V2N (Vehicle-To-Network, Vehicle-Internet) is the most widely used form of vehicle networking at present. Its main function is to make the vehicle connect to the cloud server through the mobile network, and use the navigation, entertainment, theft and other application functions provided by the cloud server.

V2V (Vehicle-To-Vehicle) can be used as information exchange and reminder between vehicles. The most typical application is for anti-collision safety system between vehicles.

V2I (Vehicle-To-Infrastructure), vehicles can communicate with roads and even other infrastructure, such as traffic lights, road barriers, etc., to obtain road management information such as traffic light signal timing.

V2P (Vehicle-To-Pedestrian) is used as a safety warning for pedestrians or non-motorized vehicles on the road.

What Can V2X Do?

First of all, we can easily think of all kinds of anti-collision, anti-rollover reminders.

In addition to anti-collision, it can also be used as a collaboration between vehicles to make the vehicles run more orderly and efficiently on the road. These include cruise control, driving queue control, adaptive communication sequence coordination and smart fleet control.

Shop Floor Collaboration

There are also warnings for vulnerable people on the road and for special emergency vehicles to make way.

Emergency Vehicle Warning

Of course, it can also improve the efficiency of travel.

V2X & ADAS

Using V2X technology can improve the security and efficiency of ADAS. Here is a typical diagram of V2X application on ADAS.

Application of V2X in ADAS

The millimeter-wave radar and camera of the vehicle itself collect the surrounding environment of the vehicle. In addition, V2X is used to obtain broader environmental parameters, such as intersection, slope information, road condition, etc. to form 360-degree computer recognition without dead ends, and to improve the active safety of the vehicle.

Thanks to the anti-collision warning provided by V2V, the safe distance between vehicles can be further reduced. The traffic control signal obtained by V2I can control the speed of traffic and select the timing of acceleration and deceleration. V2P ensures the safety of roadside pedestrians. Under the action of these three factors, the traffic efficiency of roads can be greatly improved.

V2X provides the ability to collect data that ADAS developers can use to simulate and refine to continuously improve the auto-driving prediction experience.

C-V2X Standard

The V2X industry is divided into DSRC and C-V2X standards and industry camps.

First, DSRC short-range wireless communication standard, based on IEEE802.11p and V2V as its main application mode, has formed a traditional automotive electronics industry chain such as NXP/ST/Reza/automotive enterprises after more than 10 years of development history.

The second is C-V2X, which is based on LTE-R14 technology. Through LTE-V-D and LTE-V-Cell, two major technical support, including V2I, V2V, V2P and other applications, are currently in the critical stage of standard formulation. In September this year, the first version of the standard was formulated, forming an industry battalion mainly composed of communications industry chain enterprises such as Huawei, Qualcomm, telecommunication operators and automotive enterprises.

As the world's largest automobile market, China has not yet introduced any standards, but it is imperative to set standards for automobile networking. Compared with 802.11p DSRCC, C-V2X has obvious advantages:

1. Based on cellular network, it can be multiplexed with current 4G and future 5G networks, and the deployment cost is low.

2. Wide network coverage, clear profit model of network operation.

3. The 3GPP standard has been formulated and is globally universal. With a single LTE chipset, the module cost has been greatly reduced.

4. C-V2X continues to evolve as an important component of 5G.

From the current situation of LTE network with the largest global LTE network and the technical advantages of C-V2X evolution in China, C-V2X should be the first choice of domestic V2X technical standards.

Transmission Mode

C-V2X provides two complementary modes of transmission, one for proximity and one for distance from each other.

1. Direct communication (PC5 interface) is based on D2D (Device-To-Device) proximity communication service (ProSe) in LTE standard. High-speed and high-density 250Kph communication can be achieved with the PC5 interface developed by the latest standard. In an environment without LTE network coverage, adjacent devices can communicate directly.

2. Network communication (Uu interface), which uses LTE broadcasting to transfer information to another node through a V2X server.

Key Issue Resolution

V2X technology is facing three key problems to be solved.

1. Relative high speeds between vehicles result in significant Doppler effect and frequency offset. C-V2X adds four DMRS (Demodulation reference signal) signals to the design. These symbols are associated with speeds below 500 kph and ITS (Intelligent Transportation System) bands to improve the ability of high-speed channel tracking.

2. There are many road vehicles and high density of communication nodes. Random allocation may lead to collisions and conflicts between nodes. On the one hand, C-V2X enhances the transmission structure, introduces a decentralized scheduling technology with semi-continuous scheduling mode, transmits control signals and data on the same subframe, reduces intra-frequency radiation, and optimizes the use of channels. On the other hand, a new dispatch and allocation function is imported, which enables proper data resource processing in denser environments.

3. Clock synchronization, without network coverage, lacks synchronization source. C-V2X supports both base station and global navigation satellite system (GNSS) time synchronization.

Summary

V2X technology is an important component of smart car, smart transportation and auto-driving in the future. At present, it appears that C-V2X is technically safer, more efficient and more comprehensive than DSRC. With the completion of the first C-V2X standardization specification of 3GPP, we believe that the development of C-V2X technology and related ecological chains will be faster, and we will continue to pay attention to it.

Reference

【1】Kato Shuzi 《3GPP Complete First Edition Standardization Specification for Vehicle Networking》

【2】Communication Industry: Analysis of V2X and Intelligent Driving Depth

【3】QUALCOMM 《Leading the world to 5G:Cellular Vehicle-to-Everything (C-V2X) technologies》

Author：Tangzheng

Link：https://www.jianshu.com/p/ecc198efdd38

Source: Short Book