# Advancing C-V2X for Level 5 Autonomous Driving from the Perspective of 3 GPP Standards
## 2 Background
### Cellular-V2X for Autonomous Driving  
Communication plays a crucial role in attaining the objectives of AD, which is why the stakeholders assume that the current \"connected and automated vehicles\" (CAVs) will evolve into autonomous vehicles (AVs). Needless to mention for the vehicles to autonomously operate in any environment, they should be able to communicate with other vehicles and objects. Initially, such communication was based on WiFi-based technology (i.e., IEEE 802.11p/Dedicated Short Range Communication (DSRC)) [2]. However, the concept of the cellular-V2X (C-V2X) is relatively new, where the V2X communication was realized through cellular technology i.e., LTE / 4G. C-V2X is contributed by 3 GPP as an alternative to DSRC, which operates in the 5.9 GHz frequency band, a band allocated around the globe for device-to-device/short-range communication. For instance, the authors of [3] describe a complex simulation study that compares both DSRC and LTE (mode 1 and mode 3) technology in a simulated urban environment.  
The cellular technologies of 3 GPP support the communications between vehicles such that vehicles send and receive signals either through using 4G (LTE) and/or 5G. In addition, this communication process also includes connectivity with network and infrastructure either with fixed or dynamic objects. The C-V2X technology of 3 GPP uses a common frequency band reserved for ITS applications and supports the realization of V2X requirements. Through its various releases, as presented and discussed throughout this paper, 3 GPP showcased the support in realizing C-V2X through 4G (LTE), 5G, and beyond 5G (B5G) communication technologies. The efforts for the C-V2X standard introduced by 3 GPP were significant steps towards achieving the design goals of AD and other automotive verticals. The support for the automotive industry was made possible through enhancing vehicular communication by expanding 3 GPP's 4G (LTE) platform and later by Non-Standalone (NSA) 5G technology. Hence, 3 GPP Release 14 (_Rel-14_) started presenting operational scenarios for C-V2X standard.  
The C-V2X technology performs well in high-dense traffic areas and provides high reliability and real-timeliness in communication between entities i.e., vehicles, pedestrians, networks, and infrastructures. Focusing on Standalone (SA) 5G and future communications, the C-V2X helps and supports both ranges of transmissions i.e., short- and long-range communications. C-V2X is expected to be instrumental in enabling more sophisticated ITS and infotainment services when it comes to autonomous vehicles paradigm such as vehicle diagnostics, connected infotainment, pay-as-you-drive insurance, autonomous driving, collaborative autonomous driving [4], platooning [5; 6; 7], remote driving, and other safety features, etc., by leveraging the mix-range module [8]. However, the true potential of C-V2X technology may not be explored unless the proper coordination amongst the right stakeholders is achieved. These entities and their interaction generate a large amount of data and distributed decision engines, which require reliable and fitting communication bit pipes. C-V2X and 5G mobile network is expected to pave the path towards achieving the objectives of L-5 AD. For instance, to achieve enhanced perception and informed decision-making, 5G pledges the enhanced mobile broadband and ultra-reliable low-latency communication (URLLC) pillars.