Securing a communications standard for safer roads

  • 14 Jul 2021
  • Asif Hamidullah - GCF Office

Fully automated driving may take years to arrive but the demand for safer road transport means many of the technologies that self-driving vehicles will need are quickly finding their way into the advanced driver assistance systems (ADAS) technology now in development.

Though improved sensing and visual-processing technologies will absolutely be core requirements for ADAS and the systems inside autonomous vehicles, communications will provide vital support and greatly enhance the mobility experience. Cooperation is a driving force behind the integration of communications into ADAS.

Low-latency and high-reliability communications make it easier for vehicles to react to each other’s movements. If a car is on what appears to be a clear freeway it can use signals from other vehicles further ahead that may be encountering congestion to determine whether it is better to slow down and so avoid heavy braking when it approaches the affected area. Similarly, vehicles can alert others to intended lane changes and turns so that each of the others can take appropriate action. Commercial traffic may use the messages to support applications such as platooning, allowing for reduced driver fatigue during long haul operations. Trucks can improve their fuel efficiency by reducing the atmospheric drag on all but the one at the head of the convoy.

Communication need not be restricted to moving vehicles. The vehicle-to-everything (V2X) concept works by making it possible for vehicles to obtain information from devices carried by pedestrians, cyclists and other users near the road, as well as roadside infrastructure, such as traffic signals, roadside signs, and equipment used for road repairs. This infrastructure can warn oncoming vehicles of changes to road layouts as well as traffic conditions that can be used to cut energy consumption and congestion. For example, if the traffic signals at a V2X supported junction report a red signal, approaching vehicles can be told to slow in advance, leading to reduced traffic congestion at the junction itself. In light traffic conditions, the signals themselves may react to road conditions, altering their phasing to minimize the waiting time for road users on one route if no vehicles are detected on the other. 

A key advantage of V2X is that it can enhance safety even around older vehicles that are not equipped with state-of-the-art transceivers. Machine-vision systems in more advanced cars and in roadside units can detect all forms of road user and report using V2X protocols to other nearby systems on their movements.

The final component is support for vehicle-to-network communication through which in-car electronics can send notifications of their condition to suppliers and fleet operators, as well as receiving information on longer-range traffic flows and also infotainment channels. The result of all these messages is a continuously updated map of nearby road conditions, maintained in real time, that augments the operation of ADAS and autonomous systems in numerous ways.

3GPP hits the road

The key to effective V2X is reliable standards-based communication technology that ensures messages are delivered to all the vehicles that need them with minimal latency and in a variety of situations from dense urban locations to rural areas that have limited connectivity options. Cellular technology has the potential to support the largest number of use-cases thanks to its widespread coverage and so has naturally become the focus of V2X work recently. Cellular V2X (C-V2X) protocols have been defined beginning in 3GPP’s Release 14 standards, with support for both the 4G Long-Term Evolution (LTE) and 5G New Radio (NR) protocols.

Though cellular technology provides an important basis for V2X, there remains a need for vehicles and infrastructure to communicate with each other directly in a complementary fashion. This minimizes delays in time-critical situations, such as where vehicles are passing close to each other. It is far more timely and efficient to have the V2X systems interact directly in peer to peer mode, than to incur the latency of having signals relayed back and forth via the network. Release 14 takes this into account by defining the PC5 Mode 4 interface for these sidelink transmissions.

PC5 uses a number of innovations to support efficient C-V2X messaging. Location information is a key part of the message format for multicast signalling so that vehicles can quickly determine which packets they need to process. This location information helps support another key aspect of the PC5 interface: its support for connectionless, distance-based groups. The result is a system that allows vehicles within a geographic zone to share services on the fly with no need to explicitly disconnect when they no longer need to travel with that group. Other key features include high spectral efficiency to support operation in areas where there are many transmitters, as well as latency as low as 1.5ms.

Certification is essential

Seamless interoperability is critical in these systems. The complexity of the protocols as well as the huge range of use-cases and environmental situations calls for detailed analysis and testing as part of a clear certification process. To that end, the Global Certification Forum (GCF) signed an agreement with the 5G Automotive Association (5GAA) to implement a programme that will allow manufacturers to certify their C-V2X capable products in a straightforward manner. The certification program will cover both onboard unit (OBU) and roadside unit (RSU) type products where C-V2X PC5 Mode 4 communications are used. Delivering on the GCF’s philosophy of “Test Certify Connect” will be critical to ensuring ADAS implementations and autonomous vehicles can take full advantage of C-V2X and make our roads far safer and our vehicles more energy efficient.

The integration of communications into ADAS is an example of the need for interdisciplinary work in technology standards: input will be needed from multiple communities to develop the most effective standards for these systems and to ensure they can handle mission-critical situations. Ensuring the certification process works for the community calls for a diversity of interests that encompasses vehicle manufacturers and telecom specialists. This is why GCF has adopted an inclusive process that will ultimately help create a safer, more efficient road network.


To learn more or participate in the GCF C-V2X certification programme, contact [email protected]


Asif Hamidullah - GCF Office

Asif Hamidullah - GCF Head of Certification, IoT & Verticals