ified cellular V2X (C-V2X) communications with two complementary transmission modes: direct communications between vehicles and network communications. 3GPP Rel- 16 focuses on continuation of LTE-based cellular V2X and tries to address advanced use cases. These include vehicle platooning, enhanced vehicle to infrastructure features, extended sensors, advanced driving (to enable semi-automated or fully-automated driving), and remote driving. C-V2X users can benefit from the existing widely-deployed cellular infrastructure. However, since the availability of cellular infrastructure cannot always be guaranteed, C-V2X defines transmission modes that enable direct communication using the sidelink channel over the PC5 interface. 5G NR. DOI: https://doi.org/10.1016/B978-0-08-102267-2.00007-5 © 2019 Elsevier Inc. All rights reserved. 790 Chapter 7 This chapter provides a technical overview of LTE-based V2X standards as of 3GPP Rel-15 and further provides insights into the emerging NR-based V2X technologies in 3GPP Rel-16 that are expected to accelerate the realization of advanced V2X communications and to improve transportation and commute experience. The NR-based V2X is required to enable very high throughput, high reliability, low latency, and accurate positioning use cases beyond the basic safety features provided by LTE-based V2X services. Some of the use cases will involve 5G working in tandem with other technologies, including cameras, radar, and light detection and ranging (LIDAR) 1 The Rel-16 C-V2X includes use cases such as advanced driving catego- ries identified in 3GPP, ranging/positioning, extended sensors, platooning, and remote driving. 7.1 General Aspects and Use Cases The V2X communications enable the vehicles to exchange data with each other and the infrastructure, with the goal of improving road safety, traffic efficiency, and the availability of infotainment services. V2X communications, as defined in 3GPP, consist of four use cases; namely, vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), v