V2X Vehicle-To-Everything Communication The Future Of Autonomous Connectivity

V2X technology is crucial for achieving full autonomous driving as it enhances the vehicle's situational awareness beyond the capabilities of sensors like radar, camera and lidar. While these sensors are essential for detecting line-of-sight objects, V2X creates what we call a non-line-of-sight sensor that can detect objects without needing to be in direct line of sight with them. Moreover, V2X technology can work under all weather and lighting conditions, including rain, snow, low visibility, and when obstructed by impediments.

Currently automakers and infrastructure developers around the world use two distinct V2X wireless communication technologies: Dedicated Short-Range Communication (DSRC) and Cellular-V2X (C-V2X). DSRC is an older technology that utilizes Wi-Fi within the 5.9GHz spectrum for communication, whereas CV2X is newer technology leverages cellular networks, including 5G for a more comprehensive communication ecosystem. Each technology has its own unique approach and underlying mechanisms, which I'll explain in the next few paragraphs.

Dedicated Short-Range Communication (DSRC) is an IEEE 802.11p-based standard that operates in the 5.9GHz frequency band. It is built specifically for low-latency communication, typically within a range of 300 to 1000 meters. DSRC has been under development for over two decades and is designed primarily for V2V and V2I communications.

• Latency and Reliability: DSRC boasts low latency (<100ms), making it suitable for safety-critical applications like collision avoidance and emergency braking.
• Spectrum: It operates in the 5.9 GHz band allocated by the U.S Federal Communications Commission (FCC) for intelligent transportation systems (ITS). DSRC uses a 75MHz spectrum, with 7 10-MHz channels and 5MHz reserved for safety-of-life applications.
• Deployment History: DSRC has been tested and deployed across various pilot projects in the U.S, Japan, and Europe. It has gained traction in early V2X implementations, especially for applications like intersection collision warning and forward collision avoidance.

One of the key strengths of DSRC is that it is a mature and well-established standard, with clearly defined protocols that have been in development for decades. This longevity has led to a high level of reliability and stability in its applications. Additionally, DSRC has built-in security and privacy mechanism designed specifically for vehicular communication, offering strong protections with minimal computational overhead, making it efficient for in-vehicle systems. DSRC's foundation on open standards further enhances its interoperability, allowing seamless communication across different vehicle manufacturers and infrastructure providers without being blocked into proprietary technologies. Moreover, DSRC is characterized by low latency, enabling real-time communication that is essential for safety-critical applications such as collision avoidance and emergency braking.

Despite these advantages, DSRC has some notable limitations. One of the primary challenges is its range and penetration in non-line-of-sight (NLOS) conditions. Buildings, terrain, and other obstacles can hinder the signal strength, making it less reliable in urban areas. Limited scalability is another concern, as DSRC operates in a fixed bandwidth spectrum, leading to potential performance degradation in dense traffic environments where many vehicles are trying to communicate simultaneously. Additionally, in many regions particularly in U.S, the dedicated spectrum allocated for DSRC has been underutilized, leading to discussion about reallocating some of that spectrum for other purposes, which could affect the future of DSRC deployments.

In comparison, Cellular Vehicle-to-Everything (CV2X) is a more recent standard, based on 3rd Generation Partnership Project (3GPP) LTE and 5G cellular standards. C-V2X offers two communication modes: direct short-range communication (PC5 interface) and long-range cellular communications (Uu interface).

• PC5 interface: Operates similarly to DSRC for direct V2V and V2I communication, allowing vehicles to communicate with each other or infrastructure without relying on cellular networks.
• Uu interface: Enables V2N communication using the existing cellular network infrastructure. This allows vehicles to communicate with cloud-based services for real-time updates, traffic data and infotainment.

One of the key benefits of C-V2X is its range and coverage. Using the Uu interface, C-V2X can tap into existing cellular infrastructure, allowing it to cover much greater distances than DSRC, which is particularly advantageous for V2N applications like dynamic traffic management and over-the-air software updates. Additionally, C-V2X performs well in non-line-of-sight conditions, thanks to its advanced modulation and coding schemes, making it more reliable in urban environments filled with buildings and other obstacles. Another strength of C-V2X is its scalability. Since it operates over cellular networks, it can support a growing number of connected vehicles without running into the spectrum congestion issues faced by DSRC. Furthermore, forward compatibility with 5G enhances C-V2X's future potential, enabling ultra-reliable low-latency communication (URLLC) and massive machine-type communication (mMTC), which opens doors for new V2X use cases as 5G networks expand.

However, C-V2X is not without its challenges. A key limitation is its network dependency. For V2N and other extended services, C-V2X relies on existing cellular infrastructure, which may be sparse or unreliable in rural and underserved regions, limiting its effectiveness in these areas. In addition, standard maturity remains a concern. C-V2X is still evolving, and while it shows promise, its full capabilities will only be realized with widespread 5G deployment, potentially leading to compatibility and deployment challenges in the interim. Lastly, regulatory and spectrum allocation issues could pose challenges. Unlike DSRC, which has dedicated spectrum, C-V2X must compete within the crowded cellular spectrum, thought there is increasing regulatory support to allocate more bandwidth for V2X services.

Table above lists the comparison of C-V2X and DSRC:

While DSRC is a mature, proven technology, it faces limitations in term of range, scalability, and adaptability to new wireless standards. C-V2X, on the other hand, offers more flexibility, scalability, and future compatibility, particularly when combined with 5G. It provides better performance in non-line-of-sight conditions and can scale efficiency using existing cellular networks. As 5G networks expand, C-V2X is likely to become the dominant V2X technology, supporting a broader arrange of use cases, from safety-critical applications to infotainment and real-time traffic management.

In the ongoing debate between DSRC and C-V2X, C-V2X seems better positioned for the future of connected transportation, while DSRC remains a robust option for specific, highly localized V2X applications.

Testing of V2X

As V2X technology becomes more prevalent and the vehicle users begin to depend on it for their daily commute, the reliability of the technology, its associated equipment, and various on-board applications and services becomes increasingly crucial. Regardless of the type of communication either DSRC or C-V2X, vehicle manufacturers or module suppliers must take a comprehensive approach to developing and integrating V2X technology into their vehicles to ensure full compliance with applicable regulations and standards.

Testing V2X technology in real-world environments faces significant challenges due to the inherent complexity of real-world conditions. Key issues include signal degradation and interference from various sources, which can compromise the reliability of V2X communication, particularly in urban areas with obstacles like buildings and traffic congestion. Additionally, V2X system must effectively handle a wide array of driving scenarios, making it difficult to simulate the millions of potential situations that vehicles encounter, such as varying traffic densities, weather conditions, and dynamic interactions with other road users. Furthermore, testing high-speed scenarios and dynamic mobility requires maintaining low latency and reliable communication, necessitating precise synchronization and robust data transmission between vehicles and infrastructure.

The cost of testing V2X system in real-world conditions can be prohibitively high, particularly for smaller manufacturers or ecosystem partners. Deploying test fleets, building test tracks and maintaining communication infrastructure require significant financial and logistical resources. For many V2X ecosystem partners, such as startups or Tier-2 suppliers the cost of testing can become a major barrier.

Keysight provides testing solutions for both type of V2X communications using laboratory-based simulators and emulators to tackle the challenges of testing in real-working environments. Additionally, we offer automated testing solutions to ensure that V2X system implementation comply with various test specifications. Our lab-based test beds effectively simulate or emulate real-world traffic scenarios, significantly minimizing the cost, complexity and time typically required for extensive field testing.

The Keysight E6953A V2X test solution is a compact, single PXIe system designed for DSRC testing, offering comprehensive coverage of DSRC RF measurements and protocol validation. The system features the Keysight M9421A PXIe vector transceiver (VXT) module, enabling RF layer testing for IEEE 802.11p test cases. Additionally, the Keysight E6953-35200 DSRC transceiver module supports the full DSRC protocol stack, including IEEE 1609.3, 1609.4, 1609.2 and J2945/1, used in COC protocol testing. It also functions as a fully configurable, real-time On-Board Unit (OBU) or Road-Side Unit (RSU). The core software, Keysight KS8400A Test Automation Platform (TAP), offers powerful and flexible tools for creating test sequences and plans, while also including certified test cases to streamline test software development.

As previously mentioned, C-V2X is built on LTE and the evolving 5G standard, making its test requirements a moving target. Keysight provides a solution that evolves alongside C-V2X requirements. The Keysight SA8700A C-V2X test solution supports RF, protocol, and application-layer testing, while its underlying platform is designed to accommodate future 5G NR C-V2X releases. This ensures that your initial investment is protected and accelerates the deployment of technologies enabling advanced autonomous vehicle (AV) capabilities.

The foundation of this solution is the reliable Keysight UXM 5G wireless test set, combined with the C-V2X test application (C8732114A), a suite of Keysight X-Apps for C-V2X RF measurements (C87320R1A), C-V2X waveform generation (C87320R2A), an Intelligent Transportation System (ITS) stack, and application-layer testing. If you're already using another Keysight solution for 4G LTE or 5G testing, the C-V2X solution utilizes the same X-Apps and measurement algorithms found in Keysight's signal analyzers and wireless test sets.

If you have questions or comments regarding what you have just read, feel free to send me a message.

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