Convergence of V2X communication systems and next generation networks [308539]

Convergence of V2X communication systems and next generation networks

Alin Costandoiu1 and Monica Leba2

1[anonimizat], Petrosani, Romania

2[anonimizat], Petrosani, Romania

Email: [anonimizat] monicaleba@upet.[anonimizat]-to-everything (V2X) [anonimizat], increase traffic efficiency and lower the carbon emissions for a [anonimizat], [anonimizat]-driving vehicles. [anonimizat], like C-ITS (Europe – ITS-G5) and DSRC (US – WAVE) based on 802.11p. [anonimizat]. As the science evolves at an always accelerating pace, a new technology, C-V2X (LTE/Cellular based V2X) is being developed and it started taking the spotlight from already mature and well tested technologies but with less convergence towards 5G. The foundation for connected and automated cars is an optimal technology that is scalable and can evolve in the years to come. C-V2X [anonimizat] 5G mobile network. In this paper we will make a [anonimizat]. Furthermore, we discuss the proposals for spectrum harmonization followed by pros and cons of legacy and new V2X technologies highlighting the pressure of different automotive and industry associations on steering the development and deployment of these V2X communication systems.

Keywords: V2X, IEEE 802.11p, DSRC, C-ITS, Geonetworking, C-V2X, LTE, 5G, PC5, ITS-G5

Introduction

The present article gives a good overview of standards for cellular and legacy V2X technologies as well as potential future directions. First section will be an introduction into V2X landscape and necessity of standardization. The other sections of the article were organized as follows: Section 2 presents the standardization landscape analyzing key organizations and the development status. Sections 3 [anonimizat] 4 provide trends and directions for future releases the road towards cellular V2X communication in Europe and in the U.S. Finally, Section 5 offers a conclusion of the article.

General information

Either it takes the form of combat sports or two technology confronting each other vying to become an industry standard, “Everyone loves a fight!" says the president of Ultimate Fighting Championship (UFC). [anonimizat], [anonimizat]-based 802.11p and cellular C-V2X, [anonimizat]-everything (V2X) communications on a global scale.

[anonimizat] V2X [anonimizat] U.S. ([anonimizat]) and C-ITS in Europe (Cooperative Intelligent Transport). DSRC is a project of U.S. Department of Transportation (DoT) focused on the Communications Access for Land Mobiles (CALM) architecture for vehicle-to-vehicle communication networks. In 2003 December 17, the FCC in U.S. adopted a Report and ordered establishing the licensing and service rules for the DSRC Service in the Intelligent Transportation Systems (ITS) Radio Service occupying the frequency range 5.850 to 5.925-GHz.

The ultimate goal of DSRC is a worldwide network that facilitates the communications between vehicles and roadside access points or other vehicles (Figure 1).

DSRC uses IEEE 802.11p, which is an approved amendment to the IEEE 802.11 standard and adds wireless access in vehicular environments (WAVE). It offers low-latency (down to 2-ms) communication of safety messages between vehicles and between vehicles and infrastructure like roadside units.

The 802.11p standard also defines how to exchange data through a link without the need to establish a basic service set (BSS), without the need of waiting for the association and authentication procedures to complete in order to exchange data.

C-ITS is the IEEE 802.11p equivalent protocol stack in Europe, covering PHY and MAC, named also ITS-G5. Similar to DSRC, it operates in the 5.9-GHz band as well. DSRC and C-ITS facilitates the communication for vehicle-to-infrastructure (V2I) and vehicle-to-pedestrian (V2P). This gives the vehicle additional awareness on top of what’s provided by advances in RADAR, LIDAR (light detection and ranging) and advanced camera systems. All these sensors are limited by their line of sight. V2X communication complements and enhances the capabilities of these sensors by delivering 360-degree non-line-of-sight view and awareness, extending the vehicle’s ability to “see” further even in foggy or bad weather conditions.

A mighty challenger to DSRC and C-ITS for V2X has emerged from the cellular industry. Called Cellular-V2X, it is designed to enhance and extend existing cellular capabilities. Similar to 802.11p based communications, C-V2X direct communications supports active safety and enhance situational awareness by detecting and exchanging information using low-latency transmission in the 5.9-GHz ITS band for vehicle-to-vehicle (V2V) as well as V2I and V2P scenarios. C-V2X can also function without the assistance of network and has a higher range than DSRC/C-ITS, that exceeds one mile, even in areas where mobile network connection is not available.

C-V2X can combine the communication capabilities of roadside units (RSUs) with the cellular network to help improve safety and support autonomous driving. RSUs are small radio base stations installed in intersections or along the side of the road (they can be part of lamp poles, traffic light poles, and electronic toll collectors) that allow communications between vehicles and infrastructure (V2I or I2V) within a localized area. The roadside units will use a high-throughput connection, as they are static with other cars on the road to build dynamic high quality maps using cameras and many data sensors on board, and share them with nearby vehicles as needed.

Many efforts are being dispensed by C-V2X supporters currently out of fear that the regulators (DoT or European Commission) may lock them out of the autonomous car storyline. As comments to the NHTSA (National Highway Traffic Safety Administration), which was considering to mandate for V2V communication the use of DSRC devices, Qualcomm said: “We believe there should be an objective evaluation based on realistic deployment models that assess variations of a mandate and market penetration of 4G LTE and 5G devices that include C-V2X capabilities”.

Figure 2. give a brief overview of the use cases covered. C-V2X is using wireless connectivity to enable connected vehicles to achieve “Cooperative Awareness” for the realization of the “Basic Set of ITS Applications” as defined by ETSI (European Telecommunications Standards Institute).

The field trials will serve not only to show the benefits of C-V2X technology, as defined by 3GPP Release 14 with PC5 interface specifications, but also to demonstrate improved range, reliability, traffic density, and latency for V2X communications using C-V2X.

GSMA, which represents the interests of mobile operators worldwide, together with 5GPP have urged the European Commission to keep the European market unrestricted and fair for cellular technologies use in connected vehicles. In a GSMA paper entitled “Safe and Smarter Driving: The Rollout of Cellular V2X Services in Europe”, GSMA has pressed the Commission to have a technology-neutral approach in developing the EU’s C-ITS, and calls upon European legislators to allow the market to decide which technology prevails, showing facts and figures about superiority of C-V2X.

Necessity of standardization

A standardization process for wireless vehicular communication ensures, as in any other domains, not only interoperability but also supports regulations and legislation in the legal framework, and creates larger markets for global products. For initial deployment of vehicular communications, consistent and clear sets of standards have been created, commonly named C-ITS in Europe and DSRC in the U.S., both based on the Wi-Fi standard amendment IEEE 802.11p. Initial standard sets specifying only vehicle-to-vehicle and vehicle-to-infrastructure communication and enabling applications primarily for driver information and warning system in case of danger. This section provides an overview of the key C-ITS and DSRC protocols from the standardization point of view. Automated driving is seen as a potential new application domain for vehicular communication. We will discuss its requirements on communication specifications and potential directions for future releases of the vehicular communication standards.

An essential requirement for the worldwide deployment of V2X communication systems are global standards, which provide regulations to ensure interconnectivity among V2X sub-systems and components as well as interoperability of implementations from different vendors. Additionally, global standards also serve for many other purposes, like: open standards create trust for customers in products and services, create global markets compared to proprietary systems, help to lower development and maintenance costs, and increase competition between vendors helping to lower the production costs.

V2X standardization was addressed by several standardization development organizations (SDOs), which have produced partially overlapping specifications in Europe and U.S. The combination of standards from different SDOs is very challenging and similarly a harmonization of standards is time and resource consuming. Actually, standards do not necessarily incorporate always the latest research and state-of-the-art technologies and may also become a barrier for innovations but nevertheless the benefits of standardization are far larger than this.

Standardization landscape

Historically speaking, standardization in Europe and in the U.S. has developed in parallel with many overlaps, mainly because the activities were supported by different SDOs, research and development programs, as well as promoted by different stakeholders. In the end, these different paths led to different sets of standards. These two approaches are C-ITS (Cooperative Intelligent Transportation Systems) in Europe and DSRC (Dedicated Short Range Communication) in the U.S. While, the technical approaches of C-ITS in Europe and DSCR in the U.S. have many aspects in common, the V2X communication systems in other regions might be different, like the ITS communication system in Japan operating at 700 MHz. In ISO (International Organization for Standardization), standardization activities have led to the CALM (Communications Access for Land Mobiles) family of standards, a complex system that incorporates many communication technologies and transmission schemes into a single system. Also, ITU (International Telecommunication Union) and 3GPP (3rd Generation Partnership Project) have initiated first standardization studies. This article focuses on the most relevant standards planned for deployment in the next years, and namely the standardization of C-ITS in Europe, DSRC in the U.S. and C-V2X with PC5 interface as a global standard.

Global overview

Policy and rule makers in many countries around the glove have been preparing policies on V2X for some time, reflecting the fact that technologies for cooperative driving are continuously evolving, and automated vehicles are already being introduced in the market. More work is still needed in the areas of security/privacy, conformance, public awareness and economic sustainability for investors, since these kinds of deployment require involvement from many parties, like the state, regional and local governments and road authorities together with the private sector.

In Europe, the modernization and digitalization of transport and the use of intelligent transport systems (ITS) has increasing interest from the European Committee, due to the many benefits, like increase of road safety, address gas emission and traffic congestion issues, and support jobs and economic growth in the transportation sector.

Back in August 2008, the EC published the Decision 2008/671/EC to allocate the frequency band 5875–5905MHz (30MHz) for safety-related applications of ITS, and adopted the ITS Action Plan COM(2008)886 , with the initiatives to accelerate and coordinate the deployment of ITS systems on roads and in auto vehicles in the EU.

In July 2010, a legal framework, Directive 2010/40/EU , was adopted to accelerate the deployment of ITS across Europe, with the V2I link defined as a key priority area.

The major SDOs active in Europe in the C-ITS development area are ETSI (European Telecommunications Standards Institute) and CEN (European Committee for Standardization) with their Technical Committees (CEN TC 278 – Intelligent Transport Systems). CEN works closely with ISO to produces joint specifications. Supported by a mandate of the European Commission (EC), ETSI and CEN have created a stable and consistent set of standards for a minimal deployment of V2X communication system, which was supposed to be taken as basis for European deployment. ETSI focused on specifications and requirements for the communication system and V2V applications while CEN mainly focused on standards for V2I applications. To ensure that the standards will not conflict with national standardization activities in Europe, ETSI and CEN have produced European Norms (EN) that were approved by the National Standardization Organizations (NSOs) of the EU members and associated states. Additionally, they are made legally binding. This has been achieved through a mandate issued from the European Commission for the development of a minimum and consistent set of standards for C-ITS, completed and published in 2013. The European standardization efforts are going in parallel with activities of the Car-2-Car Communication Consortium (C2C-CC), an industry consortium of automobile manufacturers, equipment suppliers, and research organizations like ERTICO, a European organization of public and private stakeholders, and ETSI CTI (Center for Testing and Interoperability). The C2C-CC has developed a customized profile of the European C-ITS Release 1 that is restricting the large set of developed standards and complements missing specifications.

In 2013, automobile manufacturers in C2C-CC signed an agreement for the adaptation of the V2X C-ITS system. Deployment plans were developed in the Amsterdam Group [https://amsterdamgroup.mett.nl/default.aspx], a strategic alliance of stakeholders of C-ITS in Europe, with the objective to facilitate joint deployment of cooperative ITS in Europe. The Amsterdam Group includes the umbrella organizations CEDR– ASECAP–POLIS, representing stakeholders for the ITS infrastructure on highways, cities and traffic management, and the C2C-CC. There were many pilot deployment projects supporting the system introduction and concept demonstration. For example, a trilateral C-ITS corridor that interconnects Vienna–Frankfurt–Rotterdam is planned to be equipped with roadwork protection systems for highways until end of 2018 .

In November 2014, the EC launched a C-ITS Deployment Platform, a multilateral framework involving national authorities and C-ITS stakeholders (not including the cellular mobile sector) to identify the remaining barriers and to propose solutions for the commercial deployment of C-ITS systems in the EU zone.

The initial phase of the C-ITS Platform (2014–2016) has focused on the development of a common vision on the interoperability deployment of the system in the EU, including the identification of key technical, legal and commercial issues and the development of policy recommendations to address these issues. The first phase has ended with publication of an technical and strategical expert report in January 2016, which was complemented by a “cost vs. benefit” analysis and a public consultation on this topic.

In July 2016, the C-ITS Platform second phase started. The main objective was to further develop a shared vision on the interoperable deployment of C-ITS systems in the EU, by defining the common technical and legal framework to address key issues on security, data protection, compliance assessment and hybrid communication identified in the first phase, and by investigating further the benefits that C-ITS could bring in terms of autonomous driving. The 5GAA (5G Automotive Association) attended two C-ITS Platform meetings as guests during year 2017. The second phase ended with the publication of an expert report in September 2017.

In parallel, the EC has adopted and is open to various other policies which are relevant for connected, cooperative and automated mobility within EU zone. In particular, “5G for Europe: An Action Plan” – COM(2016)588 calls for the availability of 5G along main European transportation paths.

In October 2017, the Radio Spectrum Committee (composed of the EC and representatives of regulators from EU Member States) approved a new mandate for CEPT (European Conference of Postal and Telecommunications) to study an extension of the ITS-safety related spectrum band 5.9GHz, with the possibility to extend the dedicated ITS spectrum to 50MHz in bandwidth (from 30MHz currently). The document recognizes recent developments in relation to Cellular (LTE) based V2X specification for ITS, which could underpin the path to 5G connectivity for the automotive and road transport sectors. The EC also recognizes that the two V2V radio systems (IEEE 802.11p and C-V2X PC5) cannot inter-communicate with each other due to different radio access techniques. CEPT shall deliver a final report on the topic of harmonization and coexistence by March 2019.

U.S. was the first to assign a dedicated spectrum in the 5.9GHz band for DSRC-based V2X services, but unfortunately there has been a huge delay between the spectrum being assigned, and being put into use. In October 1999, the United States Federal Communications Commission (FCC) allocated 75 MHz of spectrum in the 5.9 GHz band to be used by intelligent transportation systems (ITS).

In the U.S., the relevant SDOs for V2X communications are IEEE (Institute of Electrical and Electronics Engineers) and SAE (Society of Automotive Engineers). Specifically, the 802.11 Wireless LAN and the 1609 Standards were developed by working groups from IEEE, while the DSRC was developed by the technical committee from SAE. Relying on the DSRC spectrum allocation more than 10 years ago, IEEE has developed the IEEE 1609 standard family of protocols on top of the IEEE 802.11 PHY and MAC layers. This combination of IEEE 802.11 and 1609 standards is also known as WAVE (Wireless Access for Vehicular Environment). Additional layers coming above the protocol stack, like V2X message sets and related performance requirements, are specified by SAE. Altogether, the WAVE standards, V2X message sets and performance requirements build a consistent set of standards ready for basic functionality commercial deployment.

In January 2017, the US DoT (Department of Transportation) gave a Notice of Proposed Rulemaking (NPRM) that require all new light vehicles being sold on US market to be capable of V2V communications. It tries to mandate the IEEE 802.11p as the communication technology standard for V2V, and require automotive OEMs to start implementing these specifications and requirements two years after the final rule is adopted, this being around 2019-2020 (although it gave a three-year period to accommodate automotive OEM production lines). The NPRM didn’t specify anything about specific V2V safety applications to be available within first deployment, but the it suggests that next regulations could mandate intersection safety applications. The NPRM attracted lots of attention and hundreds of responses, especially from the C-V2X supporters and promoters, but the US DoT has given no indication on when it will proceed.

In parallel, the US DOT’s Federal Highway Administration Infrastructure Deployment Guidelines were temporarily published but then withdrawn from public access. These guidelines give specifications about V2I communications, in order to help transportation planners to integrate the technologies that allow their vehicles to communicate with roadside infrastructure.

Unlike in Europe, where deployment is industry-driven and voluntarily, a regulatory decision was expected in the U.S. until 5GPP, Qualcomm and GSMA started to push rulemakes for technology neutrality approach. This rulemaking process was planned to be initiated and to make DSRC mandatory, indicating a deployment at the beginning of 2020.

In China no dedicated spectrum was allocated initially for ITS services, but the Ministry of Industry and Information Technology (MIIT) is under discussion for allocating 50MHz in the 5.9GHz band for ITS systems, on a license-exempt basis, like in all other regions.

In November 2016, the Chinese government announced the dedicated allocation of 20MHz (5905–5925MHz) for C-V2X trials in six major cities. It is possible that China will be the first country to launch C-V2X, due to bigger opening to new technologies. Research being conducted for this study suggests that C-V2X commercial launch in China could be in the second half of 2019.

In Japan, the 5.9GHz band was used by a Japanese wireless technology called Electronic Tolling Collection (ETC). Reports show that this band is considered for use to provide V2V and V2I communications, but it is unclear whether a decision will be made soon. Until now, Toyota already deployed a proprietary “ITS Connect” solution in 12 cities. Their proprietary system, ITS Connect, delivers V2V and V2I communications within a dedicated 9MHz bandwidth in 760MHz spectrum, which was reserved by the Japanese government. ITS Connect is already available on new Toyota vehicles in Japan, but until today there are not many deployments for RSUs in traffic junctions, RSUs needed for V2I communications.

In September 2016, Ministry of Communications in South Korea allocated 70MHz of spectrum in the 5855–5925MHz band for ITS services on a license-exempt basis, and finally on a technology-neutral basis.

Last year, in September 2017, Australia’s telecommunications regulator, ACMA, closed a consultation on the allocation of dedicated spectrum in 5.9GHz band for ITS application, proposing rules to follow a technology-neutral approach.

Wi-Fi based V2X (802.11p)

Dedicated Short Range Communication (DSCR) standards in U.S.

As mentioned previously, DSRC relies on the widely deployed WLAN standard defined in 2012, IEEE 802.11, which defines the physical transmission (PHY) and medium access control (MAC) (Figure 3 shows the overall DSCR protocol stack). PHY and MAC are derived from the former IEEE 802.11a standard, and adapted to the requirements for V2X communication.

Similar to IEEE 802.11a, DSRC operates in the 5 GHz band (U-NII band), but it was shifted from the regular Wi-Fi channels to some dedicated DSRC channels. These channels range from 5.855 GHz to 5.925 GHz, commonly referred as the “5.9 GHz band”. The spectrum is further subdivided into 10 MHz channels (as in Figure 4 below).

DSRC uses Orthogonal Frequency Division Multiplexing (OFDM) scheme, a state-of-the-art and widely used multi-carrier transmission scheme that is robust against interference and fading, and re-uses the same preamble and pilot design for synchronization and channel estimation. Comparing to the normal usage in Wi-Fi, OFDM operates with “half clock”, which reduces the commonly used 20 MHz channel spacing to 10 MHz and doubles the time parameters, particularly the OFDM symbol duration with the cyclic prefix. These changes attribute to the characteristics of the wireless channel in vehicular environments as it can adapt to the inter-carrier interference caused by Doppler spread due to fast moving vehicles .

The most relevant functional change for V2X communication is related to network discovery, organization and formation. In general, IEEE 802.11 defines the Basic Service Set (BSS), which represents a group of stations in the standard terminology. A BSS enables various network types such as networks with an access point or mesh networks. IEEE 802.11 legacy devices need to be members of a BSS to exchange messages. Joining a BSS implies management procedures, such as channel scanning, association, and so on. For V2X communication, vehicles in proximity range need be able to exchange data immediately, without prior exchange of control information or association to any BSS. For this, a new mode, OCB (Outside the Context of a BSS) was defined, which disables all control procedures previously used in BSS. Additionally, when a station supports several modes, it can be configured to a single mode at a time only, i.e. OCB or infrastructure mode. For MAC (Medium Access Control), stations in OCB mode use the EDCA (Enhanced Distributed Channel Access) scheme. EDCA is contention-based and applies the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) technique. Using CSMA/CA, a device first listens to the channel before starting its own transmission, similar to LBT (Listen Before Talk) in LTE. In case the channel is occupied, the device will delay its own transmission by a random duration of time. Stations differentiate data types, assign the data to different access categories (ACs), and handle the data from different access categories with other CSMA/CA-related parameters, which effectively allows the prioritization of data traffic.

The Internet Protocol (IP) is the default networking protocol for many networks from our current life. In combination with the transport protocols UDP and TCP, it is therefore also used in DSRC. However, many V2X applications apply direct communication among vehicles and between vehicles and roadside units. For this purpose, the IEEE 1609 family of standards was developed.

The WSMP (Wave Short Message Protocol) defined in IEEE 1609.3 is at the core of the protocol stack. A single hop network protocol with minimum header of few bytes, which in the end will turn to be a big disadvantage because multi hop communication if crucial. WSMP provides also the multiplexing of messages to upper layer protocol entities based on service IDs, fulfilling the role of the transport protocol.

In order to access the multiple wireless channels allocated in the 5.9 GHz frequency band, the IEEE 1609.4 standard specifies a management extension to the MAC layer for multi-channel operation. It gives more flexibility to a DSRC system with one or several wireless transceivers to efficiently switch among the channels. This can be done by separation of channels into control channels (CCH) and service channels (SCH). A service provider could broadcast service advertisement messages, that carries the channel number and other useful information. The receiver of this kind of message can tune its transceiver to a desired SSH. One of the channel switching modes defines a scheme with a single transceiver, where the time is divided into sync periods composed of CCH and SCH interval. The transceiver switches between CCH and SCH at the interval boundaries for an increased robustness.

Security procedures are defined in the standard IEEE 1609.2 and provides authentication and optional encryption of DSRC messages based on digital signatures and certificates. The authentication scheme also implies a security and a public key infrastructure (i.e. certificate authority – CA and Public Key Institution – PKI), and policies for certificate validity, certificate encryption, and certificate revocation. For protecting the privacy of drivers, certificates do not contain information about the driver, though the CA may link the certificate to a driver’s identity when requested by legal authorities (i.e. Police). Furthermore, a vehicle uses a certificate only for a limited time and changes it frequently to make tracking even more difficult for intruders.

In the facilities layer, the SAE standard J2735 defined the syntax and semantics of V2X messages. Among the various defined message formats, the Basic Safety Message (BSM) is the most important and relevant. The BSM conveys core state information about the sending vehicle, including position, dynamics, status, and size. BSM is designed for compactness and efficiency, but it can be extended by additional data elements and frames. These add-ons are optional to be included in a subset of the messages, e.g. every 2nd message. The BSM is a periodic message sent at a rate of 10 Hz maximum, which translates to 10 BMSs per second. A message rate algorithm can reduce the BSM rate to keep the load on the wireless channel below a critical level. Other message types are related to communication between vehicles and the infrastructure, and are being harmonized with the European variants (see next section).

Cooperative – Intelligent Transportation System (C-ITS) standards in Europe

The parallel research and development of V2X communications by different SDOs has led to a different protocol stack in the U.S. and Europe. This section presents the C-ITS standards in Europe in comparison to the DSRC standards. Figure 5 describes the overall protocol stack and the corresponding core standards behind it, keeping the same structure of horizontal layers for access technologies, networking & transport, facilities and V2X messages, applications, and vertical management and security entities for all layers, same as in Figure 3.

ITS-G5 is the IEEE 802.11p DSRC equivalent in the C-ITS stack covering PHY and MAC layers. The last two letters in naming indicate that it operates in the 5 GHz band. Like DSRC, it operates in the 5.9 GHz band in channels of 10MHz each, whereas the European spectrum allocation is sub-divided into part A to D (see in Figure 6). ITS-G5A with 30 MHz is the primary frequency band that is dedicated for safety and traffic efficiency applications, ITSG5B has 20 MHz for non-safety application, and ITS-G5C is shared with the RLAN band, while ITS-G5D is reserved for ITS future use.

A specific requirement for Europe is that the ITS-G5 spectrum must minimize the interferences to the 5.8 GHz band. However, the key technology features of IEEE-802.11 for DSCR and ITS-G5 are similar. On PHY layer, it applies OFDM with the same parameter set “half clocked” compared to IEEE 802.11a, with an adapted spectrum masks. On MAC layer, ITS-G5 also employs EDCA with CSMA/CA, identical to DSRC, and access categories allow for prioritization of data traffic.

Standards for networking & transport and V2X messages also rely on the IP protocol for non-safety applications, but the major difference comes when checking the protocols being used. While the usage of TCP/UDP and IP version 6 is similar, C-ITS specifies a totally different ad hoc routing protocol with additional function for multi-hop communication, named GeoNetworking described by the ETSI EN 302 636 standard series. Main feature of this protocol is the utilization of geographical coordinates for addressing and forwarding of messages. It is useful for facilitating the addressing to all vehicles that are located in a geographical area, all can become the destination point of a particular packet. While this is somehow similar to broadcasting a packet to all neighbors, the geographical addressing has the advantage of making the packet delivery independent from the communication range of a single wireless hop (which can vary from several 10 meters up to 1 km under line-of-sight conditions found on highways). Additionally, the geographical coordinates are used to forward packets locally based on the vehicles knowledge of its own position and the position of surrounding neighbors, and therefore enabling much more efficient multi-hop routing with low protocol overhead for establishment and maintenance of network routes in an highly dynamic environment with frequent topology changes. GeoNetworking can also be transmit IPv6 packets, for which the adaptation sub-layer GN6 (IPv6 over GeoNetworking) has been developed and standardized. When compared to the WSMP (Wave Short Message Protocol) in the DSRC protocol stack which only supports single-hop, GeoNetworking is optimized for multi-hop communication with geo-addressing. This feature provides more technical opportunities in application support, but has the disadvantage of an increased protocol complexity and overhead.

Standards at the facilities and V2X messages layer define more application-related functionalities specific for European market. The most relevant are the V2X messages: Cooperative Awareness Message (CAM) (ETSI EN 302 637-2) periodically conveys critical vehicle state information in support of safety and traffic efficiency application, with which receiving vehicles can track other vehicles positions and movement. It can be considered as an equivalent to the BSM in the DSRC protocol stack. Additionally, the Distributed Environmental Notification Message (DENM) (ETSI EN 302 637-3) helps to disseminate safety information in a specific geographical region. Comparing with the CAM, which is sent periodically by all vehicles, the DENM message transmission has to be triggered by an application, which offers more flexibility.

For V2I (vehicle-to-infrastructure) communications, additional services are defined to communicate with road users from the infrastructure side, to control of roadside infrastructure for priority access and preemption in case of emergency, and to provide information from the vehicles to the infrastructure (see Table 1).

Table 1 Overview of V2I services based on V2X communication (Source: ETSI TS 103 301)

These services define dedicated messages (see corresponding service in Figure 5), namely the Signal Phase & Timing (SPAT) message for IIS, the MAP message for TPS, and the In-Vehicle Information (IVI). In the signal control service message are bidirectional exchanged. DENM and CAM are also used for infrastructure-related services like INS and IAS.

Similar to the DSRC standards, C-ITS applications are not fully standardized. Only minimum functional and performance requirements for three groups of applications are defined:

Road hazard signaling (RHS): includes use cases such as emergency vehicle approaching, hazardous location and emergency electronic brake lights.

Intersection collision risk warning (ICRW): refer to potential vehicle collisions at intersections

Longitudinal collision risk warning (LCRW): refer to potential vehicle rear-end/head-on collisions.

Cellular based V2X (4G and future 5G)

V2V communications are based on device-to-device (D2D) communications defined as part of ProSe services in Release 12 and later in Release 13 of the 3GPP specifications. Sidelink aims to enable D2D communications within legacy cellular-based LTE radio access networks. This feature was initially introduced for commercial purpose but later new applications were found. Sidelink has been further developed in Releases 14, it has been enhanced for vehicular use cases, specifically addressing high speed up to 250Km/h and high density with thousands of nodes.

D2D connectivity can be useful to public safety and commercial communication use-cases, and recently to vehicle-to-everything (C-V2X) scenarios. In legacy LTE communications, two UEs communicate through the Uu (Over the air) interface and data are always going through the LTE eNB. Differently, Sidelink enables the direct communication between multiple UEs in proximity of each other using the newly defined PC5 interface, and data does not need to go through the eNB (see Figure 7). Services provided in this way are also called “Proximity Services” (ProSe) and the UEs supporting this feature are named “ProSe”-enabled devices.

Resources assigned to the PC5 interface are taken from the UL, from the subframes on the UL frequency in FDD or from the subframes assigned to UL in TDD. The reasons for this selection, first, the UL subframes are usually less occupied than those on the DL; second, most of the DL subframes are never really empty so that they can be reused, unless they are empty MBSFN subframes (Multicast Broadcast Single-Frequency Network). Usually there are always at least the cell specific reference signals (CRS) transmitted in all DL subframes.

There is a difference between ProSe and Sidelink and the terms cannot be used interchangeable. ProSe describes the end-to-end application, here the D2D communication, whereas Sidelink describes the channel structure (see Figure 8). Logical channels, transport channels, and physical channels which are used in the air-interface to realize the ProSe application. There are further Sidelink channels for the other ProSe applications, the ProSe direct discovery, which are not treated in this article.

There are two SL logical channels defined for communication: Traffic Channel (STCH) and the Broadcast Control Channel (SBCCH):

The STCH is used for the data transmission to carry the user information for the ProSe application. It is a point-to-multipoint channel, reflecting the group call property of the ProSe communication, similar to GeoNetworking defined in ITS-G5 (Wi-Fi based European version). STCH is connected with the Sidelink Shared Channel (SL-SCH), a transport channel which may have a collision risk, depending on the resource assignment from the eNB. It gives the interface to the Physical Sidelink Shared Channel (PSSCH), which carry the data over the air;

The SBCCH carries signaling data useful for synchronization in the out-of-coverage or partial coverage scenarios and also for synchronization between UEs that are located in different cells. It is connected with the transport channel Sidelink Broadcast Channel (SL-BCH) with a predefined transport format, which is possible because the blocks from the SBCCH are all of the same size. The Sidelink-BCH interfaces with the Physical Sidelink Broadcast Channel, the PSBCH, which carry signaling over the air.

The Physical Sidelink Control Channel (PSCCH) is the equivalent to the PDCCH in legacy cellular traffic over Uu . It contains the Sidelink Control Information (SCI), which carries the information the receiving UE requires in order to be able to receive and demodulate the PSSCH. So, the SCI is always sent in advance to an STCH data block.

In order to support V2V communication for speeds up to 250Km/h, a few fundamental modifications to PC5 air interface have been introduced:

additional DMRS symbols have been added to handle the high Doppler associated with relative speeds of up to 500Km/h and at high frequency (5.9GHz ITS band being the main target).

for distributed scheduling (a.k.a. Mode 4, see Figure 9) a semi-persistent transmission based with sensing mechanism was introduced. Usually, V2V traffic from a device is mostly periodic in nature. This technique is utilized to sense congestion on a resource and to estimate future congestion on that resource. Based on this estimation the UL resources are booked. This technique optimizes the use of the channel by enhancing resource separation between transmitters that are using overlapping resources.

the design is scalable for different bandwidths including 10 MHz bandwidth.

Based on fundamental link and system level changes, in Cellular V2X communication there are two possible high level deployment configurations currently defined, and illustrated in Figure 9.

Both configurations use a dedicated carrier for V2V communications, meaning the target band is only used for PC5 based V2V communications. In both cases GNSS (Global Navigation Satellite System) is used for time synchronization. This can be seen as a drawback for the C-V2X systems while operating in tunnels or area where GNSS signal is missing.

In “Distributed Scheduling” (Mode 4) scheduling and interference management of V2V traffic is supported based on distributed algorithms implemented between the vehicles. As specified earlier the distributed algorithm is based on sensing with semi-persistent transmission. Additionally, a new mechanism where resource allocation is dependent on geographical information is introduced. Such a mechanism counters near-far effect arising due to in-band emissions.

In “eNB Scheduling” (Mode 3) scheduling and interference management of V2V traffic is managed by the eNBs via control signaling over the Uu interface. The eNodeB will assign the resources being used for V2V signaling in a dynamic manner.

According to the requirements, ProSe communication has to work in regions, where network coverage is missing. Therefore, ProSe communication is specified for the following scenarios (see Figure 10):

In the “in coverage scenario”, the network controls the resources used for ProSe communication. It may assign specific resources to a transmitting UE, or may assign a pool of resources the UE selects from. This way, interferences with the cellular traffic is avoided and in addition the ProSe communication may be optimized.

For the “out-of-coverage” case such a control is not possible. The UE uses resources which are preconfigured, either in the mobile device or in the USIM of the UICC card. However, the term out-of-coverge has to be interpreted carefully. It does not mean that there is no coverage at all. It rather means that there is no coverage on the frequency used for ProSe direct communication, although the UE might be in coverage on a different carrier for cellular traffic.

A special case is given in the partial coverage case. The UE out-of-coverage uses the preconfigured values, whereas the UE in coverage gets its resources from the eNB. A careful coordination between the network and the preconfigured values is necessary in order to enable communication and to limit the interferences to UEs at the cell boundary near an out-of-coverage UE.

The PC5 air interface, in ProSe communication system, is connectionless. There is no equivalent to the RRC connection procedures from legacy LTE system. Messages are created on the application level of the UE and transmitted with the first opportunity. If a connection is required, it has to be done within the application. For transmission and reception of the associated data packets, the following protocol stack is used (see Figure 11).

LTE-Uu interface can be unicast, multicast or broadcast transmitted via MBMS (Multimedia Broadcast/Multicast Services).

3GPP Release 14 including C-V2X is a key step to the next generation of cellular technology, and namely 5G. Naturally C-V2X is already on a backwards compatible evolution path with enhancements being specified beginning with 3GPP Release 15.

5GAA, a new cross industry association, 5G Automotive Association, is fully committed to support further development and implementation of this future proof technology, in order to ensure that the full potential of the C-V2X technology is realized. This includes leading efforts to address key technical and regulatory issues, as well as integrating vehicle platforms with advanced cellular connectivity, networking and computing solutions.

Spectrum usage harmonization

Technology-neutrality of the regulatory bodies

Giving the fact that FHWA (Federal Highway Administration) in US and European Committee had preferred 802.11p V2X as main technology for enabling C-ITS, the 5GAA association and GSMA asked both regulatory bodies to keep and respect neutrality when it comes to technology being used worldwide. Regulators shall facilitate interoperability regulations between technologies while the market should decide which one is more suited and optimal for a strong foundation in order to remain sustainable for years to come.

Industry associations, car and equipment manufacturers that worked hard on the development and testing of the DSRC and C-ITS are pushing strongly regulators for adopting these technologies as primary ones for mass deployment considering they are very mature and well tested.

On the other hand, V2X ecosystem worldwide needs to be developed on a future proof technology that can adapt and evolve continuously towards next generation networks like 5G. As a compromise solution, harmonization of 802.11p based and cellular based technologies were taken into consideration and pushed by 5GAA.

5GAA is a relatively new global cross-industry association of companies from the automotive, technology and telecommunications industries who share the common goal of improving road safety. Created in September 2016, 5GAA’s mission is to accelerate the global deployment of intelligent transport and communications solutions. In pursuing this mission, 5GAA aims to address society’s connected mobility and transportation safety needs.

5GAA urges the FHWA to consider how it can facilitate the deployment of infrastructure and networks supporting C-V2X. As explained herein, by leveraging existing cellular infrastructure and continued industry investment, deployment of C-V2X technology potentially can be achieved at a fraction of the cost of other competing technologies and result in a faster paced role out. Further, CV2X offers the potential for future safety enhancements as 5G technologies are developed and deployed. In addition, C-V2X’s use of the commercial cellular network potentially offers added safety features that are not available with non-cellular devices. By considering how it can facilitate the deployment of infrastructure and networks supporting C-V2X, the FHWA will help ensure that American drivers have access to a technology that potentially is more cost-effective, more dynamic, and safer than other solutions.

Today the European market has interest in two distinct technologies for Intelligent Transport Systems (ITS) and the provision of vehicle to vehicle communications: 3GPP LTE-V2X and IEEE 802.11p.

The technology neutral nature of spectrum regulations in Europe means that both LTE-V2X and 802.11p have equal rights to operate in the 5.9 GHz band, subject to compliance with the relevant regulatory technical conditions. 5GAA is a supporter of LTE-V2X as today’s performance of Cellular V2X (C-V2X), and as a platform to evolve towards 5G technologies.

5GAA address to European Commission and FHWA the issue of co-channel coexistence between the two technologies in 5.9 GHz band. This is a critically important issue for the ITS industry, and that it is beneficial for all stakeholders to arrive at a proportionate, fair, and pragmatic solution to resolve this matter, and allow the market to proceed with the deployment of ITS equipment. Ultimately the scope of C-ITS deployment is to increase the safety on the roads, increase the efficiency of traffic and lower the fuel consumption, indirectly protecting the environment.

Spectrum usage harmonization in Europe

C-V2X and 802.11p use different physical layers and medium access control protocols. Therefore, the operation of the two technologies in the 5.9 GHz band and in the same geographic area without an agreed coexistence solution would result in mutually harmful co-channel interference. Such interference can be mitigated in the short term by allocating so-called safe harbor channels to C-V2X and 802.11p in the 5875-5905 MHz band (see Figure 12).

In the short-term, the proposal is to allocate distinct 10 MHz channels at 5875-5905 MHz to each of the two technologies, while the final configuration will apply full sharing of all available channels across the two technologies. The latter will require further studies on appropriate sharing mechanisms and thus cannot be provided from the beginning.

The proposed spectrum partitioning shall happen in three steps. Partitioning of 5875-5905 MHz might be complemented by additional technical mechanisms which would allow each of C-V2X and 802.11p to access the remaining 20 MHz in a fair manner, with a reduced risk of harmful co-channel interference.

It is believed that the proposed approach would greatly facilitate the coexistence of C-V2X and 802.11p in 5.9 GHz band, and this approach will encourage stakeholders to further develop this proposal and come to a speedy agreement on this for the benefit of the European ITS industry as a whole.

The below regulatory measures all refer to the ETSI Harmonized Standard EN 302 571, which is developed by ETSI TC ERM TG37, and defines requirements for operation of ITS equipment in 5855-5925 MHz, covering the essential requirements of article 3.2 of the Radio Equipment Directive (2014/53/EU). According to ECC (European Communication Committee), ITS equipment complying with EN 302 571 are exempt from individual licensing for operating in this band.

The band 5855-5925 MHz is subject to the following harmonization measures in Europe:

The European Commission has harmonized the band 5875-5905 MHz for safety-related applications of Intelligent Transport Systems in the European Union via the legally binding Commission Decision 2008/671/EC.

The same harmonization is applied by the ECC via ECC Decision (08)01, which additionally indicates that CEPT administrations shall consider within a future review of this Decision the designation of the frequency sub-band 5905-5925 MHz for an extension of ITS spectrum.

ECC also recommends, via ECC Recommendation (08)01, that CEPT administrations should make the frequency band 5855-5875 MHz available for ITS non-safety applications.

It should be emphasized that the principle of technology neutrality in the European spectrum regulations implies that any radio technology which can demonstrate conformance with the essential requirements of the Radio Equipment Directive, through compliance with EN 302 571, can operate in 5855-5925 MHz spectrum.

An example of this is shown in Figure 12 below, where the two technologies are referred to as Technology A and Technology B. In this example, Technology A and Technology B equipment is tuned to operate at 5875-5885 and 5895-5905 MHz, respectively, thereby avoiding any co-channel interference between the two V2X technologies.

The above proposed positioning solution is naturally in line with the fact that the initial deployment of any V2X technology in 5875-5905 MHz requires a preselected 10 MHz channel for exchanging safety-related information. As the deployment of the two technologies matures, technical solutions such as mutual detect-and-vacate can be put in place to enable access to the remaining parts of 5875-5905 MHz band and eventually to the entire 5855-5925 MHz band by the two technologies in a fair-manner, with a reduced likelihood of harmful co-channel interference.

Figure 12 illustrates step 2 in the partitioning, an example of such a detect-and-vacate solution for C-V2X and 802.11p coexistence at 5.9 GHz. Once again, the two technologies are referred to as Technology A and Technology B. Here, Technology A equipment would operate without any special measures in 5875-5885 MHz. If Technology A equipment wished to transmit in 5885-5895 MHz, then they would need to monitor activity on the relevant channel, and proceed with transmissions if and only if Technology B transmissions are not detected in the said channel. A symmetrical procedure would apply to Technology B. In other words, Technology B equipment would operate without any special measures in 5895-5905 MHz. If Technology B equipment wished to transmit in 5885-5895 MHz, then they would need to monitor activity on the relevant channel, and proceed with transmissions if and only if Technology A transmissions are not detected in the said channel.

Figure 13 illustrates step 3 in the partitioning, an example of an extended detect-and-vacate solution for C-V2X and 802.11p coexistence at 5.9 GHz. Once again, the two technologies are referred to as Technology A and Technology B. Here, Technology A equipment would operate without any special measures in 5875-5885 MHz. If Technology A equipment wished to transmit in 5885-5905 MHz, then they would need to monitor activity on the relevant channel, and proceed with transmissions if and only if Technology B transmissions are not detected in the said channel. A symmetrical procedure would apply to Technology B.

Once the technology matures, it is envisioned that a full sharing of the entire 5855-5925 MHz band can take place. Suitable sharing mechanisms could be specified in ETSI EN 302 571 on the basis of the results of studies to be undertaken at ETSI, and put together in a relevant ETSI technical report (TR). There are precedents in Europe for use of such mechanisms to manage the risk of interference in license exempt spectrum.

It would be greatly beneficial for the ITS industry to rapidly converge on a pragmatic solution to the issue of co-channel interference at 5.9 GHz between the two leading technologies for V2X communications, namely LTE-V2X and 802.11p.

ITS industry to will further develop, and cope with this agreement on the spectrum partitioning, with a view to expedite the successful deployment of C-V2X and 802.11p in the 5.9 GHz band.

Road to Cellular V2X

Not so long ago, when C-V2X was gaining momentum as first release of 3GPP Rel.14 was published, studies about the readiness of 802.11p technologies were published and pushed to regulators. These studies were highlighting how C-V2X is only in the early stages of development and it will take many years until readiness for commercial deployment, most optimistic scenario was for C-V2X readiness by 2020-2021. Analyzing the market today, there are already many successful C-V2X trials in US, Europe and China (e.g. Continental and Huawei in Shanghai, China; AT&T, Ford, Nokia, Qualcomm in San Diego, U.S.).

As an initial compromise solution, harmonization of 802.11p based and cellular based technologies were taken into consideration. Then studies about analysis of performance in isolation scenarios (only one of the 2 technologies mass deployed) started to be submitted to European Commission. This is a subtle approach of presenting the advantages of C-V2X over 802.11p.

The modem chipset vendors involved in 5GAA do not plan as future deployment in smartphones with 802.11p capable chipsets.

In 2016, a European strategy on C-ITS was published, setting out priorities for the deployment of C-ITS, with a goal of services being introduced by 2019. This strategy drew on results of cost–benefit analysis14 to assess the costs and benefits associated with the deployment of C-ITS services across the EU. At that time, the technology being specified to provide C-ITS services in Europe was based on the IEEE 802.11p standard, although using cellular infrastructure for V2I, rather than deploying dedicated roadside infrastructure, was recognized as a means of accelerating infrastructure penetration across all roads from the very first launch of C-ITS services, thus ensuring that the full capability of V2X can be achieved. Since then, the mobile industry has developed C-V2X specifications within Release 14 of the 3GPP specifications for LTE/4G, in the expectation that 5G-based C-V2X will be analyzed in 3GPP specifications from Release 16 onwards. Initial 5G deployment, providing enhanced mobile broadband services, will be specified starting from Release 15.

The 4 major chipset vendors Intel, Qualcomm, Huawei and Samsung which are members of 5GAA provide nearly all of the communication chipsets used in connected cars on our roads today. These vendors are committed to provide C-V2X chipsets. The new 3GPP Rel-14 chipsets are available for first tests from the end of 2017. The availability of these chipsets will coincide with planned validation and testing of the communication modules by vehicle manufacturers including supportive vendors Audi, Continental, Ford, Nissan, PSA, SAIC and Bosch.

Further testing including interoperability tests among chipset manufacturers and across vehicle manufacturers are targeted to be conducted by mid-2018.

The focus of this testing and validation aims to confirm the functional capabilities of C-V2X, and V2V communications in particular. These production oriented chipsets look to build on the successfully tested pre-standard versions in 2015 and 2016, which showed a measured technical advantage in all safety relevant parameters including vehicle speed, distance, scalability and reliability when compared to similar tests performed across V2V and V2I use cases over IEEE 802.11p based Direct Short Range Communication (DSRC) protocols (US), ETSI-ITS G5 (EU) and CEN/ISO protocols. These validation tests are an essential prerequisite to ensure a successful launch of the first commercial chipsets in the second half of 2018, which would coincide with the announcements made by Qualcomm and Rohde & Schwarz.

Vehicle manufacturers forecast starting production tests with the C-V2X V2V commercial chipsets and communication modules in 2019 to enable them to be on track for commercial deployments in 2020. In terms of regional deployments, 5GAA expects that the first commercial deployments will occur in China and Europe, but that deployments in the US and other parts of Asia will follow soon after.

By deploying the communication stack of C-V2X instead of DSRC/802.11p the well-developed C-ITS framework will be reused, maximizing the synergy. This also includes the Security Credential Management System (SCMS) which will especially benefit from C-V2X including the distribution of security credentials, profiles and Certificate Revocation Lists (CRL) which will be available to be distributed via cellular networks.

One additional safety benefit of C-V2X is the additional support for Vulnerable Road User (VRU) collision avoidance, due to the integration of V2N and V2P (vehicle to pedestrian) functionality. This ensures that a VRU can become visible to vehicles in a first step via V2N utilizing smart phone applications carried by the pedestrian or cyclist, and will not require the integration of smartphones with C-V2X functionality in the first step of deployment. In a second step, via direct V2P communication between vehicles and VRUs, this feature will be implemented.

C-V2X also has distinct capabilities that can be complementary to automated vehicle technologies and enable an enhanced experience and improved safety of highly automated driving. C-V2X offers a path in further 5G standardization to support significant increases in data transmission requirements that are paramount to automated vehicle technologies including the support for the exchange of:

Sensor data for collective perception (e.g., video data)

Control information for platoons from very close driving vehicles (only a few meters gap)

Vehicle trajectories to prevent collisions (cooperative decision making).

These enhancements will not possible in other V2V and V2I technologies such as DSRC or ITS-G5.

5GAA highlighted several regulatory decisions need to be made in order to start a commercial deployment of C-V2X, in particular, decisions around the use of the ITS 5.9GHz spectrum.

The decisions requested by region are:

Europe: There should be an agreement on how the 5.9GHz band can be shared amongst technologies designed for the same purpose. These technologies will need to ensure that they can coexist in a technology neutral way as stipulated in the EU directives.

China: The 5.9GHz spectrum allocated for testing needs to be extended to include commercial use and deployment which is expected during first half of 2018.

United States: The 5.9GHz spectrum which has been allocated to be used for DSRC needs to be made available for C-V2X traffic safety applications in alignment with the technology neutral approach requested and supported by a large subset of the transportation ecosystem.

These changes when made will help ensure a smooth transition to 5G including the ability to leverage the benefits of C-V2X as early as possible. It also allows for further enhancements by future architecture and design decisions including network slicing, quality of service, edge clouds, and a plethora of innovation leveraging the C-V2X foundation.

Rohde & Schwarz, a leading supplier of test & measurement equipment, is enabling vehicles to move to the next level of autonomy by providing initial support for cellular vehicle-to-everything (C-V2X) signaling testing. Rohde & Schwarz and Qualcomm Technologies have collaborated by using the R&S CMW500 wideband radio communication tester with a pre-commercial Qualcomm 9150 C-V2X chipset, which supports 3GPP Release 14 specifications for PC5 based direct communications. The 9150 C-V2X chipset is a product of Qualcomm Technologies and operates in bands 46D and 47 for 5.8/5.9GHz ITS spectrum.

Both C-V2X and IEEE 802.11p technologies have the potential to bring safety and efficiency benefits to transport. However, using currently defined Long-Term Evolution (LTE) technology for V2V communication, combined with LTE cellular networks for V2N, has the potential to bring additional benefits, including:

better coverage for V2N, by exploiting existing cellular network coverage provided using lower-

frequency spectrum

reduced infrastructure deployment costs and improved service reliability, by using existing mobile infrastructure, and thus leveraging cellular technology integration and economies of scale, rather than building independently operated roadside infrastructure

the potential for V2X and other telematics services in vehicles (e.g. infotainment) to be provided via a common cellular interface

increased deployment flexibility, including the ability to provide coverage for both short-range and wide-area applications

the opportunity for integration with smart-city and other connected-transportation initiatives that also use cellular technology

enhanced security, through use of mobile subscriber identity module (SIM) cards

certainty of future evolution to 5G, facilitating earlier deployment and after-market deployment.

C-V2X test platforms and equipments were installed in Ford vehicles using the Qualcomm 9150 C-V2X solution to facilitate direct communications, and are complemented by AT&T’s 4G LTE network communications and ITS platform that takes advantage of wireless base stations and multi-access edge computing technology from Nokia. For the new communication technologies being deployed, McCain will help facilitate the effective integration with existing and emerging traffic signal control infrastructure.

Testing will support direct C-V2X communications operating in the 5.9 GHz ITS spectrum to explore the safety enhancements of vehicle-to-vehicle (V2V) use cases, including “do not pass warning”, “intersection movement assist”, and “left turn assist” among many more. The trials also supported advanced vehicle communication capabilities for improved traffic efficiencies, such as real-time mapping updates and event notifications relayed using AT&T’s cellular network and Nokia Cloud Infrastructure.

The technology company Continental and Huawei have conducted field trials to test the efficiency of the Cellular Vehicle to Everything (C-V2X) communication standard in Shanghai with positive results. C-V2X is emerging as a promising wireless communication technology, demonstrating strong potential for use in automated driving and intelligent mobility. C-V2X allows road users to communicate leveraging LTE and in future, the 5G mobile network. It is also designed to directly connect vehicles with each other as well as with the infrastructure and further road users. Even in areas without mobile network coverage, C-V2X communication allows an exchange of time sensitive and safety critical information, for example about warnings of potentially hazardous situations.

Conclusions

By leveraging existing cellular infrastructure and continued industry investment, deployment of C-V2X technology can be achieved at a fraction of the cost of other competing vehicle-to-everything technologies. Consequently, C-V2X technology potentially will save taxpayer money that otherwise would be used to deploy, maintain, and upgrade roadside units utilized by non-cellular technologies.

C-V2X has the advantage of a higher spectrum efficiency and supports larger ranges compared to non-cellular technologies. In addition, with support from the entire cellular ecosystem, C-V2X is incorporated into the latest cellular standards with a planned upgrade path for enhanced safety features. Subsequent versions of C-V2X may offer the potential for future safety enhancements as 5G technologies are developed and deployed.

On the other side, the IEEE 802.11p is a ready to deploy technology that could save lives and make the traffic more efficient from today if mass deployed. It has the advantage of many years of research, development and testing.

The path to fully automated vehicles will require coexistence for a period of time between vehicles with no active control systems and varying levels of automated vehicles, including fully automated vehicles. V2X technology will help enable this coexistence by ensuring that both fully automated vehicles and drivers of other levels of automated vehicles maintain complete awareness of nearby vehicles and other roadway hazards. C-V2X technology is well positioned to implement the full slate of V2X benefits listed above.

Qualcomm was a big player also for DSRC and offers second-generation 802.11p DSRC chips but now their focus is more towards cellular V2X, announcing the interruption of 802.11p enabled chipsets. Field trials are already ongoing utilizing a pre-commercial form of the 9150 chipset in Germany (with Audi) and France (with Peugeot).

As until now, the trend is to adopt both 802.11p and C-V2X technologies and let the market decide which one is more suited for commercial deployment and future development and evolution towards 5G.

A study from Analysys Mason from December 2017 indicates that LTE-V2X (PC5) outperforms 802.11p in reducing fatalities and serious injuries on the EU roads. This is due to a combination of the superior performance of LTE-V2X (PC5) at the radio link level for ad hoc/direct communications between road users, and the market led conditions which better favor the deployment of LTE-V2X in vehicles and in smartphones, and include a clear evolutionary path towards 5G-V2X. For these reasons, it is essential that EU regulations remain technology neutral and do not hinder the deployment of LTE-V2X (PC5) in favor of 802.11p for the provision of direct communications among vehicles and between vehicles and vulnerable road users.

An absence of interoperability at radio link level between LTE-V2X (PC5) and 802.11p is unlikely to present a substantive barrier to the reduction of road accidents in the EU in the short to medium term. The relatively low penetration of C-ITS technologies in vehicles in the first half of the next decade (and perhaps even later) means that a vehicle equipped with LTE-V2X (PC5) or 802.11p is far more likely to collide with a vehicle that is not equipped with C-ITS technologies at all – indeed it is not until the middle of the next decade that penetration rates are expected to reach a level which results in significant impacts on accident rates. Any regulations which mandate LTE-V2X (PC5) to be backward interoperable with 802.11p will therefore have only a limited effect in the early years of deployment pre-2025. Such regulations will run the risk of unnecessarily distorting the market in favor of 802.11p, thereby obstructing the adoption of LTE-V2X (PC5) and resulting in greater road fatalities and injuries in the longer term.