The number of vehicles on the roads increases every day. And everyone drives in their own way – slow, fast, aggressive and so on. Some travel the same route daily while some are driving roads they’ve never been on before. Vehicles may be more comfortable and have more safety features than in the past, but they get stuck in unavoidable situations such as traffic jams during rush hours and more rarely in collisions.
One of the reasons collisions occur is tailgating. Accidents can occur if the distance between two vehicles is not sufficient for the following car to stop safely if the driver in the first car slams on the brakes. The stopping distance of a car largely depends upon the reaction time of the driver and the breaking distance.
Collisions can be avoided if vehicles maintain a safe distance, which is possible if they accelerate and decelerate together. To achieve this, the following driver must continuously monitor and adjust their speed to maintain a safe distance from the car in front.
Now, imagine a world where many vehicles can talk to each other and work together to maintain safe distances between them. The vehicles brake, accelerate and decelerate in unison with no time lag. This capability is called vehicle platooning.
Vehicle platooning refers to a group of digitally connected vehicles that travel very close together so that they appear to move like a train. Vehicles dynamically join and leave a platoon. Vehicles in a platoon share data such as speed, breaking intentions and acceleration. It helps in reducing the safe-distance between vehicles and improves overall fuel consumption.
Another problem that connectivity can improve is traffic congestion. Traffic jams are typically caused by a large number of vehicles following the same route at the same time resulting in congestion of some roads while others nearby remain uncrowded.
This imbalance can be avoided by autonomous vehicles sharing their schedules and destination information with a centralized entity residing in the cloud. The entity can optimize route that each vehicle takes to minimize traffic congestion and reduce overall fuel consumption. Depending on the level of automation (LoA) of the vehicles, they can either be controlled by the driver in the car, remotely by human operators or by the autonomous vehicle itself. (See Figure 1.)
Figure 1. The Five Levels of Automation (LoA)
The higher the LoA, the more stringent the performance requirements of the inter-vehicle communications need to be. For example, for fully automated vehicles, the maximum end-to-end latency could be reduced to 3 milliseconds (ms), with the reliability of 99.99 %. The figures would be more relaxed for lower LoAs.
Widely deployed LTE-based networks provide the opportunity for the automobile industry to realize the concept of connected cars, also called vehicle-to-everything (V2X). (See Figure 2.) Entities within the V2X network collect and communicate data within their local environments, such as information received from vehicles or sensors that they process and share.
Figure 2. The Four Elements of V2X Communications
Vehicle-to-Vehicle (V2V), Vehicle-to-Pedestrian (V2P),
Vehicle-to-Infrastructure (V2I) such as Road Side Units (RSUs), Vehicle-to-Network (V2N)
Figure 3 provides a schematic of the V2X deployment with 3GPP network infrastructure. Presently, the 3GPP network can be LTE for V2X applications, but 5G (New Radio) is required for higher performance applications such as vehicle platooning and fully autonomous driving due to 5G’s ability to deliver very low latency and high throughput. The V2X Control Function in Figure 3 is a logical function that is used to provide the vehicle with the parameters necessary for V2X communications. The V2X Application Server is used to exchange the UL/DL Data from/to the UE in the vehicle.
Figure 3. The Simplified V2X Architecture
LTE provides support for V2X applications by defining additional QoS (QCI 75, 79) parameters. The UE—a vehicle in our case—communicates the V2X capability to 3GPP network based on the V2X services that are authorized. Based on its subscription, the bit rate requirements are communicated to the eNB that manages the resources. The V2X capabilities are also communicated during the handover procedure to the target eNB, which helps the target eNB preform the resource management and admission control.
Some vehicles are equipped with modules supporting only LTE while others may be equipped with modules supporting 5G. If a vehicle on NR cannot communicate with a vehicle supporting LTE, the vehicle supporting LTE can be regarded as another vehicle with no V2X capability. For the vehicle supporting both 5G and LTE, the handover will happen when the vehicles move out of 5G coverage as depicted Figure 4.
Figure 4. Vehicle Mobility from 5G to LTE
3GPP 5G NR specifications are maturing, the NSA (Non- Standalone) mode is already released few months back (Rel-15). As per 3GPP, the SA (Standalone) mode i.e. Rel-16 (3GPP phase 2) is expected to be completed in Dec-2019.
With the SA mode features like eMBB (enhanced Mobile Broadband), uRLLC (ultra-Reliable Low Latency Communications) and mMTC (massive Machine Type Communications), the vehicles will be able to exchange high throughput information, more reliably and seamlessly. The enhanced V2X services using 5G NR may start getting deployed and commercially available from 2020 onwards.