# Advancing C-V2X for Level 5 Autonomous Driving from the Perspective of 3 GPP Standards
## 1 Introduction  
Autonomous driving is no longer hype but a reality. Industry, the research community, and other stakeholders including authorities have been working on realizing the objectives of different levels of autonomous driving (AD). This is evident by the plethora of research contributions and activities around the globe. Standardization bodies have also been active in pushing the core research and vision of the stakeholders toward such realizations. Amongst others the 3 rd Generation Partnership Project (3 GPP) has been contributing to the technological standardization for realizing different AD use cases. The focus of standardization activities remained across the different communication-relevant solution components of AD. This was obviously boosted after the major original equipment manufacturers (OEMs) and regions such as the USA and European Union decided on 5 th-generation (5G) as the technology of choice for cellular vehicle-to-everything (C-V2X). This also shifted the paradigm from simple V2X communication to a number of communication modes including Vehicle-to-Vehicle (V2V), Vehicle-to-Pedestrian (V2P), Vehicle-to-Network (V2N), Vehicle-to-Infrastructure (V2I), Vehicle-to-Network-to-Pedestrian (V2N2P), Vehicle-to-Infrastructure-to-Network (V2I2N), etc. Obviously, the C-V2X is a concept known to the community and industry prior to the design and commercialization of 5G, which was thenknown as long-term-evolution-V2X (LTE-V2X). Meaning thereby, vehicle-to-everything (V2X) communication supported by 4 th-generation (4G) mobile network technology. Standardization and commercialization of 5G mobile network technologies have pretty much addressed the most crucial issues of vehicular communication (specific to AD) enabling the stakeholders to realize the design goals ofLevel-5 (L-5) AD.  
C-V2X has attracted huge attention in the recent past from industry, academia, and research community, the consequence of which is a large number of standard documents, design approaches, technical specifications, and reports on key issues and solution components. Obviously, such resources are not mutually exclusive and mostly overlap in contents (though the degree of overlap may vary). The current literature does not provide a simple yet easy-to-understand categorization of the technical specifications and reports. For example, [PERSON] et al. [1] provide general aspects rather than a full overview to cover all aspects of V2X applications. One may see the obvious challenge here i.e., a problem similar to finding a needle in a haystack. Finding the key support areas for V2X services is yet another open challenge to be resolved. To address these and similar challenges, we extensively analyze the 3 GPP standards relevant to AD in general and C-V2X communication in particular. It is important to reiterate that 3 GPP is a standardization body and a consortium of seven telecommunication organizations that develop standards. Therefore, we aim to analyze 3 GPP's reports and specifications for advanced cellular communication technologies i.e., 4G and 5G. With the help of these technologies, 3 GPP provides various concepts that help to realize the true potential of vehicular communication for higher levels of autonomous driving. Furthermore, we performed categorization of the technical documents, which is also inspired by the flow of 3 GPP file server documentation, topics and scope of each document, and major communication platforms i.e., 4G and 5G mentioned in each technical document.