OnQ Blog

Let’s set the record straight on C-V2X

Apr 25, 2018

Qualcomm products mentioned within this post are offered by Qualcomm Technologies, Inc. and/or its subsidiaries.


Since 1985, Qualcomm has had a leadership role in the development of wireless technologies. Today we’re the global #1 fabless semiconductor company, #1 semiconductor supplier in telematics and Bluetooth car connectivity, and a top contributor to both 3GPP and IEEE 802.11 specifications.

Our expertise in wireless technologies has allowed us to accelerate innovation not only throughout the mobile industry, but also the automotive industry. In fact, we’ve worked with the automotive industry for more than 15 years by collaborating with industry leaders and supporting automakers with the technologies and platforms to help power connected and autonomous vehicles with a variety of communications, location, and computing solutions.

“…we have invested much time and energy in both C-V2X and DSRC and understand both intimately.”Qualcomm Technologies

In terms of cutting edge vehicle-to-everything technologies, Qualcomm Technologies is important in terms of both C-V2X (Cellular Vehicle-to-Everything, or Cellular-V2X) and 802.11p-based DSRC businesses (we commercialize chips for both). Qualcomm Technologies has commercial 802.11p/DSRC solutions today, and we announced availability of our first C-V2X direct communications chipset coming later this year. We were one of the first companies to support 802.11p and have participated in global demonstrations and pilots over the last decade. On the C-V2X side, our trials currently span the globe with announced efforts with Audi, PSA, Ford, Nissan and other ecosystem participants spanning projects in Europe, North America, China, Japan, and Korea. In brief, we have invested much time and energy in both C-V2X and DSRC and understand both intimately.

Recently, comparisons between 802.11p-based DSRC and C-V2X have been made and we believe the conclusions, which favor DSRC, are inaccurate. The confusion is largely caused by general lack of understanding and familiarity with design and implementation of advanced wireless technologies and underlying specifications such as 3GPP.

Based on our industry leadership and expertise with many forms of wireless, we believe that we are uniquely positioned to clarify the misunderstandings about C-V2X.

Two radio technologies for V2X

Two key sets of specifications for V2X direct communications exist, both technologies are designed to operate on the 5.9 GHz ITS spectrum and both are capable of working independently of the cellular network, coverage or network operator involvement, despite some confusion on that point. Here are brief descriptions of each:

  • 802.11p-based technologies: The IEEE 802.11 community adapted the 802.11a Wi-Fi technology standardized in 1999 to support the 802.11p radio, which is commonly referred to as DSRC and ITS-G5, in the U.S. and Europe respectively. The 802.11p specification was completed in 2012 and uses a half-clocked version of 802.11a, leveraging radio technology that is now two decades old and was developed for wireless Ethernet cable replacement, not high-speed mobile applications. 802.11p results show that its limited range, and undetermined record in field performance at scale — derived from susceptibility to congestion and lack of minimum performance guarantees — limits the usefulness and overall application-set that it can serve, certainly putting into question its ability to support safety. 802.11p was innovative at the time, but cars now have a number of active sensors including camera, radar, and lidar — all of which force the V2X wireless sensor to deliver additional value, including longer range and reliability especially in Non-Line-of -Sight (NLOS) scenarios, where other vehicles and buildings obstruct the vehicle’s vision systems.
  • C-V2X: More recently, the 3GPP global cellular specifications body evolved LTE Direct technology and optimized it for automotive applications as defined in 3GPP Release 14 in 2017 — commonly referred to as Cellular-V2X direct communications and known technically as PC5 or Sidelink. C-V2X benefits from being based on technology that was intended for high-speed mobile applications and has been further improved specifically for automotive use cases, based on observed issues that 802.11p faced in years of research, fundamental advancements in wireless communications, and a need to support a host of new automotive applications to support enhancements in safety and autonomous driving. C-V2X includes both direct communications and network-based communications, though in this blog post we focus entirely on direct communications that support Vehicle-to-Vehicle (V2V), Vehicle-to-Infrastructure (V2I) and Vehicle-to-Pedestrian (V2P) — though the value and importance of Vehicle-to-Network (V2N) is significant as it has delivered automotive applications from the initial basic telematics services, to connected infotainment, to now teleoperation that is designed to support driverless cars.
“C-V2X is a modern technology with superior and predictable radio performance, cost efficiency, and a forward evolutionary path toward 5G…”Qualcomm Technologies

In the nearly two decades that separate 802.11p and Cellular-V2X direct communications, advances in wireless innovation occurred, evolving from 2G cellular networks to the emergence of 5G, and a fundamental change in mobile devices. Even within the Wi-Fi arena, after 802.11a, there was 802.11b, 802.11g, 802.11n, 802.11ac, and now 802.11ax — several generations of improvements. However, 802.11p, being based on 802.11a, was not evolved and improved. 802.11p was a pioneering technology that helped foster and define some excellent protocols and applications.

However, as we now enter a commercialization phase, the industry is taking a hard look at the radio technology and realizing that attach rates, performance gains, cost implications, and a need to evolve the technology to support new advanced use cases is limited by 802.11p. These new use cases are well-supported by Cellular-V2X direct communications and its evolution to 5G, and its ability to be implemented using the cellular modem to be embedded in the majority of new vehicles — on a trajectory to nearly 100% attach rate in global vehicles. C-V2X is a modern technology with superior and predictable radio performance, cost efficiency, and a forward evolutionary path toward 5G, designed to offer great potential to help save lives in future automated driving use cases.

10 things you need to know about C-V2X

  1. 1. Readiness and time-to-commercialization: C-V2X is ready for production in vehicles starting as early as 2019, using the Qualcomm 9150 C-V2X chipset, a product of Qualcomm Technologies, Inc. and/or its subsidiaries, or other solutions from a healthy competitive ecosystem. 3GPP Release 14 PC5 is ready and it is supported by a broad ecosystem including automakers, Tier-1 suppliers, Tier-2 module manufacturers, automotive software developers, mobile operators, global semiconductor companies, test equipment vendors, telecom suppliers, traffic signal suppliers, and road operators. Evidence of this can be seen in announcements and a burgeoning 5G Automotive Association (5GAA), which has more than 80 global members including major carmakers from key regions. By design, C-V2X utilizes the ITS software and applications standardized and developed over many years, promoting automotive investments that are leveraged despite a radio swap-out. The ecosystem (automotive suppliers and software vendors) is ready for commercialization in vehicles and RSUs. C-V2X’s reduced development time is afforded by a straight-forward radio swap-out, which is common in wireless technology, changing the PHY/MAC and preserving the software and applications. Integrating C-V2X into wireless modems already being embedded in vehicles is cost effective and can thus accelerate the market attach rates for C-V2X direct communications.
  2. 2. Superior range and radio performance: Improvements in modulation and coding as well as better receivers and overall advances in technology driven by LTE can allow C-V2X to offer increased communication range (~2X in Line-of-Sight), better Non-Line-of-Sight performance, enhanced reliability (lower packet error rate), higher capacity, and superior congestion control in denser environments compared to IEEE 802.11p-based radio technology. This is simply based on basic physics. 802.11p’s well-known problems of hidden nodes in CSMA protocol can lead to excessive packet collisions; however, C-V2X is designed to make sure that two devices in close proximity do not pick resources in the same subframe — leading to improved performance in dense environments. This is confirmed by empirical analysis, simulation, lab results (see link below), and field test results. The enhancements in C-V2X direct communications lead to superior performance in different scenarios (e.g., varying road/traffic conditions and vehicles speeds) for key safety use cases today and autonomous driving in the future. Our field results with a vetted test plan and automakers with years of V2X expertise prove the superior performance of C-V2X PC5 vs. IEEE 802.11p. Initial test results show the benefits of C-V2X direct communications over 802.11p-based solutions. (See link to Ford and Qualcomm initial C-V2X field trial test results at the bottom of this list.)
  3. 3. Predictable performance: Unlike 802.11p, C-V2X direct communications is designed to deliver predictable and consistent performance in realistic scenarios based on standardized minimum performance requirements set forth in the 3GPP radio specifications. For example, 3GPP defines minimum requirements of Block Error Rate (BLER) for reliable communication for different channel conditions and speeds up to 500km/h (e.g., in presence of high Doppler, fading, time and frequency errors). Unlike IEEE 802.11p-based technologies, C-V2X direct communications transceiver/chipset vendors must comply with those specifications leading to predictable and uniform performance in the field. As 802.11p does not specify minimum performance requirements, its performance can be unpredictable and unsuitable for safety applications in realistic automotive deployment scenarios. 802.11p is prone to interference as a lack of interleaving across symbols makes transmissions susceptible to even short bursts.
  4. 4. Compatibility: C-V2X is designed to provide an evolution path to 5G and is backward/forward compatible. By design, C-V2X evolution can take advantage of the latest advances in wireless communications, while maintaining backward compatibility. Rel-14 C-V2X has a strong evolution to 5G NR-based C-V2X, which can augment Rel-14 with complementary as well as new capabilities, while maintaining backward compatibility. Rel-14 can be used for basic safety communications between vehicles and 5G NR-based C-V2X can be used for advanced vehicular use cases for autonomous driving. 5G NR-based C-V2X is designed to provide high throughput, wideband carrier support, ultra-low latency, and reliability for autonomous driving use cases, such as, sensor sharing, intent sharing, and 3D HD map updates. As C-V2X direct communication does not rely on cellular networks, R14 and future releases can operate without dependency or reliance on wireless network coverage. The C-V2X technology platform, from Rel-14 to 5G NR-based C-V2X, is safety conscious, robust, and reliable, plus it can offer rich, differentiated experiences. All this can make the car a primary use case as we usher in the world of 5G and autonomous driving.
  5. 5. Cost efficiency: C-V2X can be integrated into cellular modem chipset products, making a C-V2X-based solution cost efficient and more economical compared to 802.11p/DSRC. This analysis from technology consulting firm P3 North America details how a fully integrated system with C-V2X integration with existing LTE-based telematics units is a cost-effective solution amongst V2X implementations.
  6. 6. ITS spectrum & investment reuse: C-V2X direct communications is designed to work on ITS spectrum, and its reduced development time can be afforded by a radio swap-out, reusing many years of V2X software investment. It can benefit from established security and transport layers and application protocols defined by the automotive standards communities, including the Society of Automotive Engineers (SAE), International Organization for Standardization (ISO), European Telecommunications Standards Institute (ETSI), and Institute of Electrical and Electronics Engineers (IEEE 1609 Working Group).
  7. 7. Low-latency: C-V2X is designed for low-latency direct communications. Safety messages (e.g., road hazard warnings) can be sent using low latency transmission direct communications in the globally harmonized 5.9 GHz ITS band. C-V2X’s smallest transmission latency is at most 4ms and can be lower depending on the implementation.
  8. 8. High-speed use cases: Cellular systems have been designed for high speed mobility, unlike Wi-Fi technologies which were designed to replace Ethernet cabling. Due to lack of enhancements at the physical layer, 802.11p needs advanced receiver implementation to function at high speeds. On the other hand, C-V2X direct communications takes advantage of its cellular heritage and is designed for high-speed vehicular use cases. By design, and following extensive analyses, R14 C-V2X direct communications works up to 500 km/h relative speed in 5.9 GHz band. C-V2X direct communication signal design promotes robust performance that can be achieved at high speed without the need for an advanced receiver implementation (even though an advanced receiver implementation using coded bits is very much possible and can deliver even greater performance). Furthermore, such performance is possible by defining minimum performance requirements in presence of high Doppler, fading, time and frequency errors, unlike 802.11p.
  9. 9. Robust synchronization: C-V2X has robust mechanisms that support cost-efficient synchronization from different sources, even in the absence of Global Navigation Satellite System (GNSS). In fact, both V2X technologies rely on GNSS for location information, which is necessary for operation of ITS safety applications. Obtaining microsecond-level timing is more reliable than getting positioning information from GNSS, since timing is robust to multi-path errors. Additionally, V2X systems can lose positioning accuracy before timing accuracy is lost, in the case of weak GNSS coverage. In the absence of GNSS, 3GPP has defined a detailed protocol for vehicles to use different synchronization sources, including other cars, eNodeB, and RSU timing.
  10. 10. Security: Security focused communication is very important for any V2X applications. C-V2X can benefit from established security and transport layers and application protocols defined by the aforementioned automotive and wireless standards communities. Moreover, certificate distribution and revocation can benefit from network-based cellular communications (V2N).
“The momentum behind C-V2X is building, and it is ready for deployment in production vehicles as early as next year.”Qualcomm Technologies

C-V2X momentum is building

We hope this blog post has helped define the differences between C-V2X and DSRC and, more importantly, given you the knowledge you need to better understand the advantages of C-V2X. The momentum behind C-V2X is building, and it is ready for deployment in production vehicles as early as next year. Stay tuned for our upcoming C-V2X blog posts and announcements. Learn how Qualcomm Technologies is accelerating C-V2X technology adoption by visiting our C-V2X page, where you can find videos, webinars, presentations, white papers, and many other resources.


Opinions expressed in the content posted here are the personal opinions of the original authors, and do not necessarily reflect those of Qualcomm Incorporated or its subsidiaries ("Qualcomm"). Qualcomm products mentioned within this post are offered by Qualcomm Technologies, Inc. and/or its subsidiaries. The content is provided for informational purposes only and is not meant to be an endorsement or representation by Qualcomm or any other party. This site may also provide links or references to non-Qualcomm sites and resources. Qualcomm makes no representations, warranties, or other commitments whatsoever about any non-Qualcomm sites or third-party resources that may be referenced, accessible from, or linked to this site.

The OnQ Team