By: Natasha Taylor
Technology is increasingly changing the way we navigate our roads and the overall transportation system. One technology at the forefront of this is Vehicle-to-Everything communication (V2X), a key enabler for connected mobility.
V2X communication is implemented through Dedicated Short Range Communication (DSRC) or Cellular Vehicle-to-Everything (C-V2X), with both technologies delivering a range of use cases that are categorized as ‘day-1’ or ‘advanced’.
The day-1 use cases are those that were initially implemented through the development of V2X, and set the foundations for the usage of the technology. These use cases largely focus on improving road safety by delivering basic safety messages using V2X communication.
Advanced use cases build upon the functionalities of the day-1 use cases. However, as well as improving road safety and enhancing traffic management, these use cases enable applications such as autonomous driving, cooperative intersection control, lane merging, and platooning through the use of advanced communication protocols.
Compared to day-1 use cases, advanced use cases typically require advanced communication protocols that support high throughput, low latency, and improved reliability.
Both day-1 and advanced use cases can employ different messages, these being either ‘continual messages’ or ‘event-triggered messages’.
Continual messages are used where vehicles and road users, infrastructure and networks constantly share messages between one another. Examples of these messages include information about the location and speed of other vehicles, sensor data, or information about objects that could cause collisions.
As these messages focus heavily on safety-related aspects, they are crucial in providing consistent information to vehicles and road users, enabling any decision making to take place in a timely manner.
Day-1 use cases generally employ continual messages because vehicles and infrastructure send messages amongst each other at all times when active to provide basic safety for all road users.
Event-triggered messages are only used under certain circumstances due to a specific event that is occuring. Use case examples could include the alerts about emergency vehicles, collision warnings, or even a vehicle informing others that it is going to perform a special maneuver.
Depending on the use case, event-triggered messages can be repetitive or non-repetitive — determined by how frequently road users need to receive information.
Whilst event-triggered messages also assist in increasing road safety, they also contribute to increased traffic management and are key in enabling autonomous driving, therefore they are generally associated with advanced use cases.
Source: 5GAA ‘Study of spectrum needs for safety related intelligent transportation systems - day 1 and advanced use cases’’, published October 2021
According to 5G Automotive Association (5GAA), spectrum needs for the delivery of day-1 use cases via LTE-V2X are expected to require between 10 and 20MHz of the 5.9GHz spectrum.
Advanced cases via LTE-V2X or 5G-V2X are expected to require 40MHz or more to deliver advanced driving services. As the market evolves, the requirement could increase with the development and implementation of new use cases.
A number of groups have been identified by 5GAA to categorize both day-1 and advanced use cases. These are as follows:
Source: 5GAA ‘C-V2X Use Cases Methodology, Examples and Service Level Requirements’’, published June 2019
The first expectation is for a mass deployment of basic safety and traffic efficiency use cases as a baseline for V2X usage across regions worldwide. Building upon this, there is the anticipation for a large-scale introduction of use cases that allow for advanced safety features automated driving - something 5GAA expects to be implemented from 2024 onwards. From 2026, other additional connected automated driving functionalities, such as HD sensor sharing, are expected.