Vehicle to Everything Communications

1 Introduction

We stand at the dawn of a new age of safe intelligent transportation systems. The development and deployment of vehicle to vehicle (V2V), vehicle to infrastructure (V2I), and vehicle to pedestrian (V2P) safety communications systems collectively known as V2X, will bring the greatest advances in road safety since the invention of the seatbelt.

2 Background – V2X C-ITS

V2X systems use short range radio messages to create situational awareness about all vehicles within range (<1KM). These messages contain information about the location, direction, and velocity of the vehicle or information about safety hazards or other local information of use to the vehicle operator. Unlike all other sensors such as cameras, radar, or LIDAR that might be carried by the vehicle V2X messages are not limited by line of sight or weather conditions. This ability to “see” beyond direct line of sight allows V2X to detect safety hazards that other sensors are blind to. They also are immune to problems such as glare, and misinterpretation of images that plague vision based advanced driver assistance (ADAS) functions.

Some examples of V2V hazard warning functions:

Rear end collision scenarios

  • Forward Collision Warning: V2V monitors both the presence of a stopped vehicle and the rate of closure.
  • Emergency Electronic Brake Light: V2V will “see” through obstacles. The driver in the following car will get a warning before the truck’s brake lights come on.

Lane Change Scenarios

  • Blind Spot Warning
  • Do Not Pass Warning
  • Blind intersection warning

The potential of V2X to save lives and protect property is huge.  The US Department of Transportation National Highway Traffic Safety Administration (NHTSA) estimates that V2V hazard warnings could prevent or improve the outcome of over 3.9 Million light vehicle collisions per year saving the U.S. $500 Billion per year by 2035.

2.1 V2X or C-ITS

There are two architectural standards for vehicle-to-vehicle safety messages.  The V2V system developed by the Crash Avoidance Metrics Partnership (CAMP) in the United States, and Cooperative Intelligent Transportation System (C-ITS)  developed by the Car-to-Car Communications Consortium (C2CCC) and the European Telecommunications Standards Institute (ETSI) in Europe. C-ITS has also been adopted with some modifications by China. There are many similarities between the two systems and some significant differences.  There is also a harmonization effort underway to bring the two systems closer together over time.  The terminology V2X and C-ITS extend coverage to vehicle to infrastructure and vehicle to pedestrian and more recently vehicle to everything


  • V2X and C-ITS both use the same message integrity protections based on IEEE 1609.2 . 1609.2 is a public key signature and certificate standard that is much more compact and therefore more bandwidth efficient than traditional X.509 certificates.
  • V2X and C-ITS both use the same privacy protection mechanisms using 1609.2 pseudonym certificates.
  • V2X and C-ITS both use the same spectrum bandwidth allocation although as we will see the question of radio modulation and channel management are a matter of current debate


  • V2V depends on each vehicle maintaining situational awareness of all vehicles in the vicinity by broadcasting its own position, direction, and velocity every 100 mS. It simultaneously receives similar messages from all vehicles within range.  Situational awareness is an internal map of all nearby vehicles and their positions and motions.  By analyzing this internal map each vehicle can generate safety warnings for itself.
  • C-ITS sends Cooperative Awareness messages (CAM).  Rather than build an internal situational awareness map C-ITS participants send  specific warning messages.  For example, “Ice on road <location>”, or “Emergency braking  <time, location>”.  They can also carry less critical messages like, “e-vehicle charging station at <location>”. CSMs also include traffic advisories, recommended speeds to sync with traffic lights, etc.


V2V situational awareness is more extensible.  Since hazard warnings are generated within the vehicle they do not have to be agreed by all participants.  Therefore, any developer can write a new hazard warning at any time. The C-ITS system, on the other hand, requires agreement among all participants on the naming and nature of hazards.  It is difficult to add a new warning because the meaning of warning messages must be agreed in advance of use.

C-ITS is less computationally and bandwidth intensive.  CAMs with explicit warnings can be acted on immediately rather than analyzing a situational awareness map.

3 Trust and Privacy

There are two critical cybersecurity requirements for V2X messages; they must be trustworthy, and they must not leak private data.  Specifically, it must not be able to use V2V messages to track the location and travel of an individually identifiable vehicle.

V2X equipped vehicles with broadcast their location, direction, and speed ten times per second so that other vehicles can accurately determine if they constitute a safety hazard.  Infrastructure devices such as bridges and roadways will also broadcast informational messages such as road icing conditions, lane closures, congestion warnings and information about the timing of signal lights.  If a malicious actor were able to broadcast incorrect information such as “no hazard” rather than “ice on bridge” or broadcast location messages for non-existent vehicles they could easily create chaos in the flow of traffic as well as possible accidents, injury, and deaths. This makes the trustworthy data integrity of all V2X messages critically important.

The second critical cybersecurity requirement for V2X messages is privacy protection.  The effectiveness of V2V safety warnings will depend on having almost every vehicle participate in the exchange of messages.  A timely analogy is that the effectiveness of vaccine in stopping a pandemic is dependent on getting as many people vaccinated as possible.  However, if people fear that the V2V messages can be used to track their travels they will be tempted to turn off, disable or remove the V2V transmitter.  The V2V security system was designed to protect the privacy of users.  How it does this is a fascinating but rather complicated story of applied cryptography.  It is beyond the scope of this paper so we will not go into detail here.

INTEGRITY Security Services is the world leader in V2X  security credentials management systems (SCMS).  Automotive OEM’s around the world depend on ISS to ensure that V2V communications will be trustworthy and protect the privacy of users.

4 DSRC vs C-V2V

There has been a lot of debate recently around the choice of the radio technology underlying V2X and C-ITS.  We must point out that this is all about the lowest levels of the protocol stack, layers 1 Physical and 2 DataLink of the OSI reference model.  It does not affect either the underlying messages of V2X or C-ITS nor does it affect the security architecture of either system.

DSRC (Dedicated Short Range Communications) is a radio network technology standardized by the IEEE as IEEE 802.11p.  DSRC is derived from the 802.11 WiFi wireless local area networking standards.

C-V2X (Cellular V2X) Developed by Qualcomm and the 3GPP C-V2X offers a more modern radio protocol using cellular telephone technology. C-V2X is designed to interoperate with LTE, 4G, and 5G mobile networks as well as directly vehicle to vehicle without the support of the cellular network.

ISS does not take a position for or against DSRC or C-V2V.  Our ISS-SCMS systems can work equally well with either radio technology.