Cellular V2X: What can we expect on the road ahead?
Through evolutions in automation, electrification and cellular V2X (vehicle-to-everything) capabilities, the automotive world is undergoing a transformation which will increase safety, efficiency and mile-economy. Can we expect a smooth ride ahead? Below, we examine the technical challenges behind two key evolving vehicle-to-network use cases: C-ITS and ADAS.
For many years, cellular vehicle-to-network (V2N) communication has served many various automotive use cases (read more in our earlier LTE-V2X blog post).
However, with 3GPP Release 14, the evolution of cellular vehicle communication took a significant step forward. Not only did it feature enhanced cellular V2N communication, the new release also included standards on newly developed direct vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication for the very first time.
The evolution of cellular V2X technology continued with 3GPP Release 15 and 16, helping to fulfil the increasingly demanding requirements of advanced automotive and ITS services.
Cellular network-based solutions have provided a platform for automotive technology use cases for many years. Today, both the cellular solutions and automotive use cases they serve continue to evolve at speed. But how are they built, and which technical challenges can we expect over the coming years? We take a look below.
Cellular V2N use cases: C-ITS and ADAS
Cellular V2N connectivity enables a wide range of road transport and automotive services, including regulated Cooperative Intelligent Transport Systems (C-ITS), Advanced Driver Assistance Systems (ADAS), connected road infrastructure services, vehicle-centric OEM telematics and aftermarket services, fleet management and logistics services, and convenience and infotainment services.
Among these services, C-ITS and ADAS directly explore the potential values of road transport by improving driving safety and road traffic efficiency.
In Europe, the regulated C-ITS services provide the driver timely and trustworthy information about road hazard events, traffic signals, and road traffic situations. Typical examples of such services are emergency vehicle approach, road work warning, dynamic access control of designated infrastructure, dynamic environment zones, time to green, green light optimal speed adversary, etc. Regulated C-ITS services that are prioritized by the European Commission for the initial deployment of European C-ITS are also known as “Day-1” C-ITS services. A series of application layer standards have been released for Day-1 C-ITS services, e.g. standards developed in ETSI for Decentralized Environmental Notification (DEN) basic service and road infrastructure-based services.
Today’s ADAS systems rely on vehicle sensors for assisting the driver in driving safety. Cellular V2X connectivity can further improve ADAS by providing the driver with information about upcoming signal and traffic situations using either standardized protocols or, in many cases, proprietary protocols to vehicles from car original equipment manufacturers (OEMs) e.g. Audi’s traffic light information via V2N communication. They can even support remote drivers as showcased in the recent self-driving vehicle pilot which we developed jointly with Einride and Telia.
It can even enable the exchange of sensor and driving intention data among vehicles, for example driven by ETSI workgroups on Collective Perception Sharing and Maneuver Coordination Services.
Both human drivers and vehicles with automated driving features can benefit from connected ADAS services.
Typically, Day-1 C-ITS services require communication latency below 100 milliseconds for end-to-end message delivery between the vehicle, network and back to other vehicles. Day-1 C-ITS service messages are triggered by events or status changes in a vehicle, and usually have a size smaller than 1200 bytes. These communication requirements can easily be fulfilled with current 4G LTE networks. However, advanced ADAS services have more stringent requirements on latency, reliability, and system capacity that may only be supported with 5G systems.
Architecture of cellular network-based solutions
Compared to short-range direct V2V and V2I communication, cellular V2N communication (often referred to as V2N2V and V2N2I) – based on cellular mobile networks – provides a faster time-to-market solution for C-ITS and initial supports to ADAS services.
According to the latest Ericsson Mobility Report, LTE networks already connect millions of cars on today’s roads through infotainment and telematics services. By 2025, it is expected that the number of connected cars in operation will rise exponentially to hundreds of millions.
Delivering C-ITS and ADAS services using the existing cellular modems of modern connected cars offer both financial and time-to-market advantages, especially when compared to short-range V2V/V2I solutions that will take many years to reach the required penetration rate of on-board and roadside units. Besides, cellular network-based solutions can easily integrate smart phone and portable devices for providing protection to vulnerable road users, such as pedestrians and cyclists.
Read more about the cost equation of cellular C-ITS solutions in this 5GAA whitepaper.
The general architecture for delivering C-ITS messages over cellular networks is shown in Figure 1. This model has been trialed and piloted many times to increase both road safety and efficiency, for example:
- the driver-assist features of the Australian connected vehicle trial with Telstra and Lexus
- the EU-funded NordicWay phase 1 & 2 projects and upcoming phase 3 project which aim to interconnect Nordic road authorities and major automotive OEMs
- the Talking Traffic program in the Netherlands which aims for safer and more efficient road transportation
The general architecture consists of V2X Application Client (V2X-AC) and V2X Application Server (V2X-AS), as well as the inter-change server as an optional component ensuring the interoperability of C-ITS services across different V2X application servers.
The V2X-AC can be at vehicles, personal devices, or road-side units which are all provisioned with cellular connectivity. Function-wise, V2X-AC is divided into V2X-AC Transmission (TX) and V2X-AC Reception (RX).
V2X-AS is at the backend or edge servers that are accessible by V2X-ACs via cellular networks. A V2X-AS may include Message Reception (Msg RX) and Message Transmission (Msg TX), which handle the message communication with V2X-AC, and a Decision Engine, which processes the received message and makes decision on its further dissemination to V2X-ACs. The Message Dispatcher, if present, disseminates the message to the correct receivers according to the requirements of the services.
The V2X-AC TX transmits messages to V2X-AS using cellular uplink unicast communication. The V2X-AS uses cellular downlink unicast, multicast or broadcast to transmit messages to V2X-ACs (RX).
In this architecture, V2X messages are always processed by the V2X-AS at the application layer before being further disseminated to more V2X-ACs (RX). This is to prevent spamming or misuse of the cellular communication channel, protect the privacy of users, as well as apply filtering to ensure quality of data and policy-based rules for the dissemination.
V2X-AS may be implemented at the backend system of different stakeholders, e.g. automotive Original Equipment Manufacturers (OEMs), third-party ITS service providers, or Road Traffic Authorities (RTAs). For V2X-ACs that are connected to different backend systems to support interoperable C-ITS and ADAS services, V2X-ASs need to be interconnected via the external TX and RX interfaces for backend systems. In this general architecture, the inter-change server interconnects different backend systems via standard interfaces.
Technical challenges for C-ITS and ADAS message communication via cellular infrastructure
Geolocation-based message delivery (GeoCasting)
Many C-ITS services, especially safety-related services, need to disseminate messages to all relevant vehicles and road users in a specific geographic area, even if the identity information of receivers may not be known to the transmitter due to privacy reasons. This special feature in cellular V2X message communication is known as GeoCasting.
GeoCasting over cellular V2N communications can be realized by:
- disseminating messages which are associated with information about the target geographic area
- identifying receivers using the associated information of geographical area through a geo-fencing mechanism, implemented either at the V2X-AS side or at the V2X AC side
- delivering the messages to the identified receivers via the message dispatcher
Popular publish/subscribe IoT messaging protocols like MQTT or AMQP are often also used for implementing GeoCasting, e.g. vehicles can subscribe to channels (called topics) that are for messages relevant to a certain geographical area. The realization of such solutions will be discussed in subsequent blog posts.
QoS provisioning and continuity of services
Comparing with Day-1 C-ITS services, advanced ADAS services have more stringent requirements on the guaranteed communication latency, reliability, system capacity, and service continuity. The ongoing rollout of 5G networks offers excellent capabilities such as ultra-low latency, traffic separation through network slicing, QoS provisioning through dedicated bearers or 5G QoS flows, and fast inter-MNO mobility solutions to enable connected vehicle cross-border coverage. These all make 5G networks an ideal foundation for building solutions for future C-ITS and ADAS services.
Interoperability of services
A primary goal of C-ITS is to ensure users of the same service can interoperate with each other, to maximize the safety effect. However, automotive and transport ecosystems involve different stakeholders such as car OEMs, regional RTAs, and third-party service providers, who may adopt different implementation solutions when offering the same services. This makes interoperability of C-ITS services a challenge. A solution to this arrives in the concept of using interchange server to interconnect ITS backend systems in a scalable way. This has been developed and tested in the NordicWay phase 1 & 2 projects and served as an input to the Harmonised C-ITS Specifications for Europe developed by the EU C-Roads Platform.
Solutions for the above challenges are essential to the commercial success of C-ITS and ADAS services provided through cellular networks. In forthcoming technical blogs, we plan to further elaborate each topic.
5G cellular networks is expected to penetrate about 20 percent of subscriber markets by 2024 (Ericsson Mobility Report). Read the latest Ericsson Technology Review to find out how this will impact emerging road transport and automotive applications.
Learn more about Ericsson’s connected vehicle solutions.
|ADAS||Advanced Driver-Assistance Systems|
|AMQP||Advanced Message Queuing Protocol|
|C-ITS||Cooperative Intelligent Transport Systems|
|DEN||Decentralized Environmental Notification|
|ITS||Intelligent Transport Systems|
|MQTT||Message Queue Telemetry Transport|
|OEM||Original Equipment Manufacture|
|RTA||Road Traffic Authority|