Summary:
The main system indicators that V2X technology affects user experience include delay time, reliability, data rate, communication coverage mobility, user density, security, etc.
1. Vehicle networking system
The Internet of Vehicles is a typical application of the Internet of Things in the special industry of transportation. The reference model of the Internet of Vehicles system mainly includes three layers: data perception layer, network transmission layer and application layer.
1. Data-aware layer
The data perception layer is responsible for the comprehensive perception and collection of vehicle and road traffic information. It is the nerve ending of the Internet of Vehicles. Through sensors, RFID (radio frequency), vehicle positioning and other technologies, it can sense the vehicle condition and control system, road environment, vehicle current location, and surroundings in real time. Information such as vehicles realizes the extraction of the attributes of the vehicle itself and the external environment of the vehicle, such as static and dynamic attributes such as roads, people, and vehicles, and provides comprehensive and original terminal information services for the Internet of Vehicles. The data sources of the data perception layer include multiple parts. One is the perception of the vehicle itself, such as speed, acceleration, position, yaw angular acceleration, etc., which are mainly realized through the in-vehicle bus, GPS and other perception devices; the other is the perception of surrounding vehicles. The perception of driving status, such as the position, orientation, speed, and heading angle of surrounding vehicles, requires vehicle-to-vehicle communication, and the perception of the road environment, such as traffic signal status, road congestion status, and lane driving direction, which requires vehicle-to-road communication. Each vehicle and roadside facility unit needs to distribute the information it perceives; the third is to obtain more data, such as weather data, through background or third-party application interaction.
2. network transport layer
In order to achieve information sharing between vehicles, vehicles and roads, vehicles and people, vehicles and the cloud (vehicles and background centers), it is necessary to consider the formulation of communication protocols. The network layer integrates the data perceived by different entities in a network environment by formulating a network architecture and protocol model that can meet the needs of business transmission and can adapt to the characteristics of the communication environment, and provides transparency to the application by shielding the communication network type from the application layer. information transmission services. Through the comprehensive application of cloud computing, virtualization and other technologies, the existing network resources are fully utilized to provide powerful communication support and information support services for upper-layer applications.
3. application layer
Various applications of the Internet of Vehicles must be compatible with possible future network expansion functions on the basis of the existing network system and protocols. Application requirements are the driving force behind the development of the Internet of Vehicles. While realizing functions such as intelligent traffic management, vehicle safety control, and early warning of traffic incidents, the Internet of Vehicles should also provide users of the Internet of Vehicles with various services such as vehicle information query, information subscription, and event notification. Function. At the same time, the cloud computing platform can be used to provide comprehensive vehicle service and management functions for different types of users, including government management departments, vehicle manufacturers, information service operators, and individual users, and to share vehicle and road traffic data, thereby supporting new services. form and business model.
Due to different business requirements and transmission environments, the entire Internet of Vehicles uses different communication technologies, and an entity often has multi-mode access capabilities, such as vehicle-mounted units, which have Wi-Fi, DSRC (Dedicated Short-Range Communication), 3G/4G cellular Communication access, and satellite communication, as shown in Figure 4.
Specifically between entities, such as the roadside unit and the background center adopt the optical fiber communication subsystem, and the pedestrians, vehicles and the center adopt the cellular access subsystem. Due to traffic safety requirements and its strict communication delay and transmission reliability, real-time communication between vehicles and vehicles, and between vehicles and roads is required without interfering with other communication systems. Communication standards and the development of corresponding communication technologies. The so-called Internet of Vehicles (V2X) that is often referred to now is aimed at the chivalrous Internet of Vehicles technology such as vehicle-to-vehicle/vehicle-road communication.
2. Composition of Internet of Vehicles
According to the definition of the Internet of Vehicles Industry Technology Innovation Alliance, the Internet of Vehicles is a large-scale system network composed of the intra-vehicle network, the inter-vehicle network and the vehicle-cloud network for radio communication and information interaction. As shown in Figure 5, through the integration of the three networks, the seamless connection of communication between V2X can be realized, the communication efficiency can be improved, and communication blind spots can be reduced.
1. In-car network
The in-vehicle network is a standardized vehicle network established based on bus technologies such as CAN, LIN, FIexRay, MOST, and Ethernet. Functions such as status awareness, fault diagnosis and intelligent control. As shown in Figure 6, the in-vehicle network uses high-speed Ethernet as the backbone to connect five core domains including powertrain, chassis control, body control, entertainment, and ADAS (advanced driver assistance system). In addition to the control function, it also provides a powerful gateway function. Figure 7 shows the topological diagram of the Mercedes-Benz 222 car network bus.
2. Inter-vehicle network
The inter-vehicle network (also known as Vehicular Ad hoc Networks VANET) refers to an open mobile ad hoc network composed of vehicles, roadside units and pedestrians in the traffic environment. It establishes a wireless multi-hop connection by combining the global positioning system and wireless communication technologies, such as wireless local area network and cellular network, to provide high-speed data access services for vehicles in a high-speed moving state, so as to realize information interaction between V2X, As shown in Figure 8. The vehicle self-organizing network is the communication basis for the future development of intelligent transportation systems, and it is also the guarantee for the safe driving of intelligent networked vehicles.
3. Application of communication
(1) Dedicated Short Range Communications (DSRC)
DSRC is based on the Institute of Electrical and Electronics Engineers (IEEE), and improved on the basis of IEEE802.11 Wi-Fi technology}EEE802.11 p standard and IEEE1609 standard V2V and V2I communication protocols, it is a relatively mature and efficient wireless communication System technology, which is one of the important foundations of intelligent transportation systems, has been adopted and perfected by automobile manufacturers in Europe, Japan and other countries. Our country also adopts this technology in the highway toll collection equipment (ETC).
DSRC communication is used in the frequency band around 5.9GHz to organically connect vehicles and vehicles, and between vehicles and road infrastructure, to realize identification and two-way communication of high-speed vehicles within a range of hundreds of meters, and to provide real-time images, voice and data Information transmission, ensuring low delay and low interference of communication links and system reliability.
For example, within the effective communication distance of DSRC, the vehicle can send information such as position, speed and direction to other vehicles on the road through DSRC at a frequency of 10 Hz; at the same time, the vehicle can also receive signals from other vehicles, and when necessary (such as There is a vehicle driving out at the corner of the road, or the vehicle in front suddenly brakes suddenly and changes lanes) the signal device in the car will remind the driver to pay attention by flashing, voice reminder or vibration of the seat and steering wheel, and take necessary safety measures, as shown in the figure 9.
The DSRC system structure is mainly composed of three parts, as shown in Figure 10. They are the on-board unit (OBU), the road-side unit (RSU), and the dedicated communication link. The OBU is installed in the embedded vehicle communication unit on the vehicle, and it exchanges information with the RSU through a dedicated communication link in accordance with the provisions of the communication protocol. RSU is a fixed communication device installed in a designated place (such as next to the driveway, above the driveway, etc.), and communicates with different OBUs in real time and efficiently, and connects to mobile Internet devices through wired optical fiber, and communicates with the cloud intelligent transportation (ITS) platform. Data interaction. The dedicated communication link is the channel for information exchange between OBU and RSU, and it consists of two parts: downlink and uplink. The communication application from RSU to OBU is a downlink, which mainly realizes the function of writing information from RSU to OBU. The uplink is the communication from OBU to RSU, which mainly enables RSU to read the information of OBU and complete the autonomous identification function of vehicle status. Therefore, in the architecture of DSRC, a large number of RSUs need to be deployed to better meet service needs, and the construction investment is relatively large.
(2) C-v2x communication
C-V2X communication is a wireless communication technology for vehicles based on the evolution of cellular network communication technologies such as 3G/4G/5G, including LTE-V2X systems based on 4G networks and 5G-V2X systems based on future 5G resources. Facilities to realize V2V, V21, V2P, V2N information interaction, adapt to more complex security application scenarios, and meet low latency, high reliability and bandwidth requirements.
10LTE-V2X technology
LTE-V (Long Term Evolution-Vehicle, V2X) is a V2X technology with independent intellectual property rights in my country. It is an ITS (Intelligent Transport System) based on TD.LTE (Time Division-Long Term Evolution, long-term evolution). Intelligent transportation system) system solution, which belongs to the important application branch of the LTE follow-up evolution ecosystem.
OZLTE-V2X Protocol Architecture and Composition
The LTE-V2X standard protocol architecture consists of three parts, including the physical layer, data link layer, and application layer. The physical layer is the underlying protocol of the LTE-V2X system, which mainly provides frame transmission control services, channel activation and deactivation services, timing sending and receiving and synchronization functions. The data link layer is responsible for the reliable transmission of information, provides error and flow control, and provides an error-free link to the upper layer. Based on the services provided by the data link layer, the application layer implements related operations such as communication initialization and release procedures, broadcast services, and remote applications. The LTE-V2X system equipment consists of three parts: UE (User Equipment, user terminal), RSU (Road Side Uni, road side unit), and base station. The specific composition is shown in Figure 11.
UE includes vehicle equipment, personal user portable equipment and so on. The RSU is located between the base station and the UE, and undertakes the data communication task of V21. The base station is a device that undertakes the wireless access control function of the LTE-V2X system. It mainly completes the wireless access function, including management of the air interface, user resource allocation, access control, mobility control and other wireless resource management functions. The GPS signal communicates with the base station through the satellite ground station.
03 Analysis of LTE-V2X Main Technical Indicators
The main system indicators that V2X technology affects user experience include delay time, reliability, data rate, communication coverage mobility, user density, security, etc. Its related indicators include safety delay ≤ 20ms, non-safety delay ≤ 100ms, peak rate uplink 500Mbps, downlink 1 Gbps, support vehicle speed 280km/h, which will be increased to 500km/h in the subsequent evolution of 5G version, and reliability is almost 100%5 coverage comparable to LTE range.
Source| Software-Enabled Cars