Taking a Deep Dive into New V2X Architectures

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Emerging vehicular networking applications, such as V2X, and use cases will need stringent Quality of Service (QoS) requirements in latency, data rate, reliability, and communication range. Technologies often used in ultimately developing an autonomous vehicle center around three types of sensors: camera, radar, and LiDAR. However, vehicle-to-everything (V2X), another wireless technology that already exists, can bring significant added value to autonomous vehicles. V2X refers to high-bandwidth, low latency, and reliable communication between a broad range of transport and traffic-related sensors. 5G mobile networks will provide connectivity for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications.

In the following, we will discuss how the 3rd Generation Partnership Project (3GPP) intends to use 5G in V2X applications with significant advantages over current dedicated short-range communication (DSRC) or other Cellular-V2X (C-V2X) proposals. Worth noting is that the word cellular, in C-V2X, is somewhat misleading. In this application, cellular does not refer to a cellular network such as 5G, but instead to the technology of the basic electronics used in cellular radios, for direct communication between two radios.

A Technology Evolution is Coming

From a communication technology perspective, future Intelligent Transportation System (ITS) services are widely accepted. This will ultimately lead to autonomous driving and require a high level of connectivity in vehicles via advanced communication technology such as 5G V2X. After many years of research, driven by academia and industry, and the delivery of mature technology enablers for 5G, 3GPP is drafting the standard for 5G V2X, starting with Release 16.

Let’s first look at the definition of V2X. This vehicle-to-everything technology is a means of two-way communication that enables the transmission of information between an automotive or electric vehicle and any surrounding entity that might affect that vehicle. V2X applications will have an important impact on safety and convenience well before full autonomy becomes a reality. V2X technology will also enable less gridlock, reduce environmental impact, and add more vehicle comforts for drivers and passengers.

5G, coupled with V2X, will enhance vehicle and pedestrian safety with capabilities such as vehicle notification and control for approaching emergency vehicles with distance/direction information, pedestrians crossing in a crosswalk (traffic lights/signals will be controlled or extended for safety and during unexpected events, allowing the identification and avoidance of a pedestrian darting into traffic. When an accident is near, notification of its location and distance will be sent. Things such as school bus notifications, including unloading/loading school children in the area, will also keep pedestrians safe.

Cellular-vehicle-to-everything (C-V2X) is a subset of V2X. It will supplement line-of-sight (LoS) sensors such as cameras, radar, and lidar for non-LoS awareness, which is critical for safer driving. C-V2X will also enable larger sensing coverage than LoS sensors and is the foundation for vehicles to communicate with each other along with everything that surrounds them. 3GPP started standardization work of cellular V2X (C-V2X) in Release 14 in 2014. It is based on LTE as the underlying technology. Specifications were published in 2017.

The types of EV power transfer communications capabilities include vehicle-to-infrastructure (V2I), vehicle-to-network (V2N), vehicle-to-vehicle (V2V), vehicle-to-pedestrian (V2P), and vulnerable road users like cyclists, vehicle-to-device (V2D), and vehicle-to-grid (V2G). Figure 1.

Figure 1: The main C-V2X use cases: Vehicle-to-Vehicle (V2V), Vehicle-to-Pedestrian (V2P), Vehicle-to-Infrastructure (V2I), and Vehicle-to-Network (V2N). V2X safety messages may include Cooperative Awareness Messages (CAM) and Decentralized Environmental Notification Messages (DENM) in Europe or Basic Safety Message (BSM) in the US. (Image Source: IEEE)

The automotive industry is also pursuing ways to reduce the costs for On-Board Units (OBUs) that will support 5G V2X while avoiding/minimizing any increase of the vehicles’ prices.

5G and V2X

5G will make V2X easier, faster, and more reliable. The main difference between a 5G and V2X framework can be summarized as follows:

• 5G, like any radio mobile service, uses an infrastructure in which the landscape is divided into individual cells, widely overlapped, and managed by proper antenna systems, called base stations.
• V2X, like any wireless service, exhibits a more flexible structure, where small antenna-device systems, called hot spots, assure best-effort connections by using a strong co-operation strategy.

DSRC Versus C-V2X

The high-speed communication protocols that come into play here for vehicle safety are DSRC and C-V2X. These two protocols operate at very high speed with a high-frequency exchange of data at low latency. DSRC has a data rate of 6Mbps to 26Mbps in the 5850MHZ to 5925MHz band. C-V2x has a data rate of 26Mbps (RX) Max 26Mbps (TX). Both operate in the 5.9GHz band, and both use the same use cases and the same message sets (SAE J2735 and J2945), and both also use digital signatures for security and trust in message providers. DSRC and C-V2X radios do not connect, but they are broadcasting vehicle location, acceleration, and speed while listening to other radios.

The two technologies use different wireless standards. DSRC uses WAVE IEEE (802.11p), and C-V2X uses long-term evolution (LTE), which cellphones use. The FCC allocated the 5.9 GHz band to Wi-Fi and C-V2X in November 2020.

These two radio technologies cannot talk to each other, and their respective ranges are quite different. DSRC is around 300m, where C-V2X has lower latencies, 20 percent to 30 percent more range, and performs much better in the presence of obstructions than DSRC. Overall, C-V2X has significantly better performance. However, DSRC still does have sufficient range and reliability for key safety applications.

C-V2X Sidelinking

5G, Release 16, brought sidelinking to industry C-V2X with 5G New Radio (NR). This release advanced C-V2X applications such as platooning, advanced driving, extended sensors, and remote driving. Strict latency and high reliability must be guaranteed because of the need for emergency braking and collision avoidance in critical driving situations. C-V2X’s smallest transmission latency is at most 4ms and can be lower depending on the implementation. It is difficult to quantize reliability here, but each new Release has added another group of improvements in performance and safety, which has enhanced reliability. New releases are scheduled to continue on this path of safety and reliability improvements.

The bulk of the traffic that will be carried out by short-range communications, especially in the first phase of V2X deployment, will be periodic broadcasting messages by each vehicle communicating its status and movements.

In dense traffic areas, available channel resources will saturate and lead to an increase in packet losses. This could endanger driver and passenger safety. Congestion-control algorithms were examined and defined to modify certain parameters before these conditions reach critical levels. However, instead of looking at specific algorithms, researchers examined the Wi-Fi standard approach (IEEE 802.11p) versus the cellular standard approach (sidelinking LTE-V2X as defined by 3GPP as part of C-V2X in Release 14).

The C-V2X communication technology was developed by 3GPP to enable direct communications among vehicular user equipment (VUE) over the sidelink, also named PC5 interface. C-V2X sidelink is the first wireless system to introduce distance as a dimension at the physical layer. This will enable achieving a uniform communication range across widely varying radio environments for both LoS and non-LoS.

C-V2X includes two modes of communication from Release 14: direct mode (PC5) for the most immediate and latency-sensitive communications, and network mode (known as Uu) since it links User Equipment to the UMTS Terrestrial Radio Access Network. It uses an existing cellular network for broadcast-type communications.

For the PC5 mode:

• Mode 3 (scheduled) in which the sidelink resource assignment is performed with the supervision of the eNodeB and requires cellular infrastructure support for radio resource management.
• Mode 4 (autonomous), where resource and interference management is performed by vehicles in a distributed manner and does not involve cellular infrastructure (and can be used in areas without cellular coverage).

Security and Privacy in V2X Communication

LTE-based V2X communication uses a high capacity, large cell coverage range, and widely deployed infrastructure to support various types of vehicular communication services for safety and non-safety applications. Technical organizations such as 3GPP and Qualcomm have already prepared the roadmap toward 5G-based V2X services.

Security defined in 3GPP mainly includes confidentiality, integrity, authenticity, and resistance to replay attack.

New privacy and security challenges, including secure mobility management for group-oriented autonomous platoons, reliable cooperative driving, efficient and privacy-preserving vehicular big data sharing and processing, and more, demand more investigation in 5G vehicular networks.

In the scenario of the possible solutions for automotive security and safety assurance against any cyberattack, the full adoption of a double-key cryptosystem is advisable.

V2X applications depend on continuous, detailed location information, which can lead to privacy concerns. In a privately owned vehicle, location traces will reveal the movements and activities of the driver, who might or might not be the owner of the vehicle. In short, sending and disseminating V2X user location information might have a possible privacy concern for the owner and driver of the vehicle.

Other V2X applications include communication between vehicles that will augment existing methods to help with left- or right-turn assistance, emergency braking warnings, and improved situational awareness at intersections. Extending Waze concepts can control or suggest speed adjustments to account for traffic congestion and update a GPS map with real-time updates on lane closure and highway construction activity. V2X in some form is essential to support over-the-air (OTA) software updates for the now-extensive range of software-driven systems in your car, from map updates to bug fixes to security updates and more.

V2X safety messages can be made to include a Basic Safety Message (BSM) in U.S. standards or Cooperative Awareness Messages (CAM) and a Decentralized Environmental Notification Messages (DENM) in a European Union (EU) standard.

BSM contains position, velocity, and acceleration information and is transmitted up to 10 times per second. This message system also enables the vehicle receiving unit to predict collisions and warn the driver.

V2X Message Protection and Security

V2X and V2I communication need strong security to protect messages against fraudulent or misleading use that might lead to safety and privacy issues. Another method for security is signed messages using Public Key Certificates that are used to prevent unauthorized parties from interfering with the exchange of data and to pseudonymize the communication securely.

Public key infrastructure (PKI) consists of policies and procedures used to create, manage, use, save and revoke digital security certificates. PKI allows for the transfer of electronic information securely and goes beyond just passwords as authentication with a requirement of more rigorous identity confirmation.

5G New Radio (NR) Intention Sharing

Intention or trajectory sharing will enhance autonomous driving by providing a higher level of predictability and traffic efficiency in advanced path planning.

5G New Radio (5G NR) will enable intent sharing with:

• High throughput: 5G can provide the required high data rates needed, such as greater than 100Mbps in a 1km stretch.
• High reliability: 5G can ensure that trajectory information will be shared accurately and promptly.
• Low latency: 5G low latency capabilities will allow trajectory information to be shared within a few milliseconds.

C-V2X Performance in Crowded Highway Situations

The 5G Automotive Association (5GAA) ran V2X performance and functional tests in a test report entitled V2X Functional and Performance Test Report, in which C-V2X technology was tested for a highly congested scenario in a laboratory setting. Even in this congested scenario, C-V2X latency remained bounded by the 100ms latency budget configured for that scenario, which is a very positive result.

In a series of laboratory and field tests, it is observed that:

• C-V2X communication in 20MHz CH183 has the same reliability performance (Packet Reception Ratio vs. distance) as the identical BSM-like message transmission in 10MHz CH184.
• Impact of C-V2X high load transmissions in CH183 on DSRC basic safety transmissions in CH172 is negligible up to a 1.4-km range in Line of Sight (LOS) conditions.
• Impact of C-V2X high load transmissions in CH183 on V2I and I2V transmissions in CH178 is negligible up to a 1.4-km range in LOS conditions.
• Impact of C-V2X high load transmissions in CH183 on V2I and I2V transmissions in CH180 is negligible up to 1km in LOS conditions.

Ford and Qualcomm performed additional field tests supporting the latest 5GAA petition for waiver with the Federal Communications Commission (FCC) for C-V2X deployment. Those tests by Ford showed C-V2X with a very acceptable performance, especially in LOS conditions.

According to the 5GAA website, C-V2X was deemed ready for deployment with commercial chipsets and was also seen as ready to start in-vehicle deployment in the 2020/2021 timeframe globally. The 5GAA will partner with the relevant Standards Developing Organizations (SDOs) to drive the requirements of 5G V2X to create a successful V2X ecosystem.

Conclusion

The FCC effectively changed the vehicle communications Cooperative Intelligent Transport Systems (C-ITS) market in the U.S. via the restructuring of the 5.9GHz band.

The automotive industry must go forward on a narrowed spectrum with C-V2X technology instead of the widely used Dedicated Short Range Communication (DSRC). The changes announced pave the way for progress, eliminating the uncertainty caused by competing technologies.

V2X and 5G are fast-becoming integral technologies for automakers as it endeavors to commercialize fully autonomous vehicle technology in the years ahead. After the launch of C-V2X vehicles in China in 2021, Ford anticipates bringing the technology to all of its vehicles sold in the U.S. beginning in 2022. The 5GAA will partner with the relevant SDOs to drive the requirements of 5G V2X to create a successful V2X ecosystem.

IHS Markit, a financial services company, posted an analysis on 5G, C-V2X, and automotive connectivity for the 2021 year on its website in January 2021.

According to a news release about a C-V2X study published on Market Watch:

“The V2I communication segment is expected to grow at a CAGR of over 12% over the forecast period due to the increase in the adoption of smart traffic infrastructure. The smart traffic infrastructure involves smart traffic signals and smart surveillance cameras, which communicate with vehicles to provide information about traffic and road conditions.”

More exciting vehicle advances are coming, which will significantly change the way we drive our vehicles for the better.