Busting Myths About Cellular Vehicle-to-Everything (C-V2X)

The confluence of connected vehicles with Advanced Driver Assistance Systems (ADAS) is accelerating the race towards the autonomous vehicle and Intelligent Transport Systems (ITS). Timelines have been condensed as advancements and road testing with autonomous vehicles is increasing in pace, and, from a technology perspective, 2020 as a date for some form of commercial implementation is becoming increasingly feasible.

Within cooperative ITS communication, dedicated short-range communications (DSRC) relates to two-way secure wireless communications for safety applications between a roadside infrastructure and vehicles or mobile platforms for ITS applications. The two major components of DSRC are on-board equipment (OBE) and roadside equipment (RSE) that use the 5.9 GHz spectrum in Europe as well as the US. The auto industry has worked on this for a long time, together with a broad range of global standardization organisations, although implementations in Europe and the US are different.

Meanwhile, C-V2X has emerged as a possible alternative to DSRC. C-V2X is an interesting hybrid technology that attempts to provide a way of bridging historic automotive ETSI-ITS/IEEE/SAE software developments with current cellular state of the art radio technology, to provide a global platform that can be scaled and evolved to embrace emerging 5G technologies.

The C-V2X modem standard defines two transmission modes that work together to enable a broad range of automotive use cases. One is direct communication, including vehicle-to-vehicle (V2V), which allows vehicles to communicate with each other using the 5.9GHz ITS spectrum without a network being present. The technology also allows vehicles to communicate directly with pedestrians using smartphones (V2P).

Vehicle-to-infrastructure (V2I) communication is also possible, for example between vehicles and stop signs or traffic lights. V2V, V2I and V2P enhance LTE Direct device-to-device communications, introduced in 3GPP Release 12 for high-speed vehicular use cases and automotive safety. It does this by using the PC5 Interface standardized in 3GPP Release 14, enhanced to deal with high Doppler, improved synchronization and lower latency, to enable exchange of real-time information between vehicles traveling at speed and in high-density traffic, regardless of a network being available.

For the first time, it establishes a paradigm where a SIM card is not necessary for communicating, allowing cars to broadcast messages with their location, direction and speed to other cars typically every 100 milliseconds. This mode means there is no requirement for a central entity to tell all the devices what to do, and therefore it works both in and out of network coverage.

The second mode is network communication that can leverage existing infrastructure, optimized for LTE broadcast and unicast (eMBMS), as well as the ubiquitous coverage of existing LTE networks to deliver additional services, such as alerts about an accident a few miles ahead. Vehicle-to-network (V2N) communication provides the opportunity to acquire and broadcast additional safety information, as well as efficiently deliver HD video and AR/VR applications. This second mode is suitable for more latency-tolerant use cases, and utilizes the Uu interface so the network can communicate with vehicles using the cellular broadcast system, while they can communicate with the network via unicast over the regular WAN connection. Although the network and direct modes complement each other, but the important distinction is that the direct mode doesn't rely on network assistance and coverage, making it more suitable for safety use cases.

In this time of rapid change, it's key for all parties to be aware of the basics of existing and emerging technologies, including the fundamentals, such as C-V2X not needing a network but being enhanced by having access to one. For more information and myth-busting, join the upcoming Light Reading/Qualcomm webinar "10 Facts You Need to Know About Cellular-V2X" on Thursday, December 7, 2017, at 11:00 a.m. New York / 4:00 p.m. London time.

This blog is sponsored by Qualcomm.

— Steve Bell, Senior Analyst, Heavy Reading