What is LTE-V2X (PC5)?

LTE-V2X (PC5) is a proxy standard that represents the subset of the 3GPP Release 14 specification that defines Cellular Vehicle-to-Everything (C-V2X) technology which uses device-to-device communication (PC5) at 5.9 GHz without requiring the presence of a base station. 

LTE-V2X was standardized by the 3GPP in 2016 under the umbrella of LTE Release 14 and encompasses two interfaces: 

(a) A wide area network LTE interface (Uu) that connects end-user devices and vehicles to mobile network base stations and mobile core networks, for provision of Internet and vehicle to network (V2N) services

(b) A direct communications interface (PC5) that connects vehicles to vehicles (V2V), to roadside infrastructure (V2I) and to pedestrians and other vulnerable road users (V2P), for provision of low-latency and high-reliability vehicular services. The LTE-V2X (PC5) interface does not necessarily require assistance from a mobile network.

LTE-V2X (PC5) is based on LTE Sidelink, a technology that was originally an adaption of the core LTE standard that allows direct communication between two LTE devices without going through a base station. It was mainly used for public safety communications. LTE-V2X (PC5) standard redefines LTE SIdelink for C-V2X so that an LTE-based technology can be used by vehicles to communicate wirelessly with other vehicles, smart infrastructure and pedestrians directly without the need for a base station. This technology is key to autonomous driving, as vehicles will need to transmit their position, speed and other parameters to the network and other cars around them. Similarly, they will have to listen to what the network and other cars are transmitting.

This device-to-device communication mode of C-V2X includes direct communications between vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), and vehicle-to-pedestrian (V2P). LTE-V2X (PC5) communications use the dedicated Intelligent Transportation Systems (ITS) 5.9 GHz spectrum that works independently of cellular networks. The ITS 5.9 GHz spectrum band is dedicated by governments worldwide to enable vehicles to talk to each other without any interference. In comparison to other standards for ITS 5.9 GHz communication like Dedicated short-range communication (DSRC) or 802.11p, LTE-V2X (PC5) provides an increased communication range, better non-line-of-sight (NLOS) performance, enhanced reliability, and cost efficiency.

LTE-V2X (PC5) will play a major role in making vehicles increasingly autonomous. It can give rise to the following interesting scenarios for autonomous driving in the future:

• Platooning: LTE-V2X can help up to three vehicles to form a convoy in which the vehicles are very close to each other and they all slow down or speed up simultaneously. The distance between the vehicles is so less that it can't be achieved by human drivers. This platooning will make better use of road space, save fuel and make the transport of goods more efficient. Platooning is not possible for more than three vehicles, as transferring information between vehicles will take too long which will hinder synchronous braking and it also needs the low latency cellular network infrastructure that will be deployed with 5G.
• Co-operative driving: LTE-V2X can also minimize the disruption caused by lane changes and sudden braking by keeping them connected with each other and helping them work together. For example, to re-enter a slower lane during periods of dense traffic. LTE-V2X can inform the front vehicle in the slow lane to accelerate slightly, and the car behind to slow down slightly to make sufficient space for the merging car.
• Avoiding Collisions: LTE-V2X broadcasts the identity, position, speed and direction of vehicles to each other so that the onboard computer can evaluate whether any other vehicle is on a potential collision trajectory. If there is the possibility of a collision, then the vehicles concerned can be alerted and evasive actions like braking or accelerating could be taken to avoid a collision.

Click here to learn about V2X and C-V2X.