**Devendra Naga ([email protected])**
V2X is a vehicle to everything technology that allows the vehicles to be aware of their surroundings such as the other vehicles around it, enviornmental conditions, road conditions and many more.
This is an ongoing WIP document.. stay tuned for more.. i will update as and when i have free of time..
The technology basically uses an adhoc mode of communication (either using the 802.11p radio or using the LTE device-to-device communication interface - called as PC5) to send out various set of information about the vehicles, envionment or the things as such stated above.
Since its all an air medium of communication and usually is a broadcast manner, there is a chance of a fake messages from bad actors. This is somewhat avoided using the authentication technique used in PKI.
So that when a message is sent over the air, it is then signed and a signature is being attached to the message before it sent over the air. When a receiver, receives this message, performs what is called the verification of the message to validate if its a fake or real message and delivers / drops.
The data and information content with in the V2X messages is very detailed and some what of a good quality to be used in the autonomous cars. If not autonomous, the data is still be useful in doing an passive safety system to perform collision avoidance.
it comes to the mind that, since the communication media is air interface, it must follow some kind of networking stack or its own networking stack.
The system basically uses a parallel communication stack avoiding to go through the heavy ip / ipv6 protocol stack in order to make it quick and avoid routing and excessive L4 and L3 delays.
in order for every other unit to understand each other, the protocol group formed a set of standards - one in US and one in EU.
US standards are followed by the IEEE and SAE groups and in the EU the ETSI ITS group is doing the standards.
one of the base line standard for both the US and EU is 802.11p that defines radio requirements and uses and channels to operate on to.
ETSI follows a more generic and more advanced software stack. The below diagram explains the ETSI protocol stack architecture.
|-------------------------------|
| ETSI Day1 applications |
|-------------------------------|
| ETSI Facility Layer |
|-------------------------------|
| ETSI BTP/GN layer |
|-------------------------------|
| ITS G5 |
|-------------------------------|
This translates to ISO model as the following
ITS G5 -> Layer 2 (wireless) ETSI GN -> Layer 3 (networking) ETSI BTP -> Layer 4 (TCP/UDP) ETSI Facility -> http / ftp / telnet / protobuf .. ETSI Day1 applications -> browsers / content generators ,viewers.. (in vague terms)
Each layer has its own (more than one probably) have the protocol standard being published by the ETSI ITS group.