# Advancing C-V2X for Level 5 Autonomous Driving from the Perspective of 3 GPP Standards
## 1 Introduction
### Case of Interest of This Paper  
The 3 GPP has been supporting vehicular communication through 4G and 5G technologies. In this paper, we focus on analyzing and simplifying the 3 GPP contributions in relation to the support provided for realizing the higher level of C-V2X applications. We present our case of interest as follows:  
* 3 GPP standardizes for a large set of use-case scenarios when it comes to supporting vehicular communication (in general) and C-V2X in particular. One major contribution of this work is to conduct extensive analyses of the 3 GPP C-V2X standards, which are compiled in a way to guide better the readers, research community, and industry.
* The 3 GPP standard documents provide various key issues and their potential solutions, which will help in realizing the true potential of a higher level of C-V2X communication. A literature survey shows that there is a clear lack of resources that present most (if not all) key issues, assumptions, and solutions. Hence, in this article, we elaborate on all of these and present easy-to-comprehend content by discussing these together and their roles in achieving the L-5 AD. We believe this will equip the readers and researchers in a way allowing them to study the right potential solutions for the challenges of their interest. This will assist in evolving the research work leading towards achieving the solutions of higher autonomy levels.
* 3 GPP is a large body of various strong partners and there exists a large amount of support for different categories of V2X communication. Therefore, we performed an exhaustive study of 3 GPP standard documents and presented a categorization of the documentation about V2X services.
* The available standard documents tend to introduce ignorance of the readers. Therefore, we provide an easy-to-follow discussion for the readers about use cases, challenges, communication requirements, and potential solutions. This simplified version of the discussion aims to build readers' involvement by making their interest in 3 GPP standardization.  
* The work provided by 3 GPP for standardized V2X communication is complex to understand and therefore, we provide a simplified structure of 3 GPP documentation and technological standards of intelligent transportation systems (ITS) services to achieve L-5 AD.
* The current standpoint of 3 GPP standardization for V2X services places little or no emphasis on the intelligence part in vehicular communication. In this regard, we highlighted the missing gaps for introducing intelligence in the execution of different network operations for enabling the use-case scenarios.  
The rest of the paper is structured as follows. Section 2 presents the background of C-V2X and 3 GPP, followed by the taxonomy of C-V2X related 3 GPP standard documents in Section 3. The support for 4G & 5G, and 5G based V2X services are presented in the Section 4, and Section 5, respectively. Section 6 presents the network data analytics function, followed by the future directions in Section 7. Finally, Section 8 elucidates the conclusion of the paper.