IEEE 802.11bd & 5G NR V2X: Evolution of Radio Access Technologies for V2X Communications (1903.08391v2)

Abstract: With rising interest in autonomous vehicles, developing radio access technologies (RATs) that enable reliable and low latency vehicular communications has become of paramount importance. Dedicated Short Range Communications (DSRC) and Cellular V2X (C-V2X) are two present-day technologies that are capable of supporting day-1 vehicular applications. However, these RATs fall short of supporting communication requirements of many advanced vehicular applications, which are believed to be critical in enabling fully autonomous vehicles. Both DSRC and C-V2X are undergoing extensive enhancements in order to support advanced vehicular applications that are characterized by high reliability, low latency and high throughput requirements. These RAT evolutions---IEEE 802.11bd for DSRC and NR V2X for C-V2X---can supplement today's vehicular sensors in enabling autonomous driving. In this paper, we briefly describe the two present-day vehicular RATs. In doing so, we highlight their inability to guarantee quality of service requirements of many advanced vehicular applications. We then look at the two RAT evolutions, i.e., IEEE 802.11bd and NR V2X and outline their objectives, describe their salient features and provide an in-depth description of key mechanisms that enable these features. While both, IEEE 802.11bd and NR V2X, are in their initial stages of development, we shed light on their preliminary performance projections and compare and contrast the two evolutionary RATs with their respective predecessors.

• The paper presents a comprehensive analysis of the evolution from DSRC and C-V2X to IEEE 802.11bd and NR V2X, addressing the need for high reliability and low latency in advanced vehicular communication.
• The paper details the use of advanced PHY and MAC techniques—such as midambles, LDPC coding, and flexible scheduling—to boost throughput and extend communication ranges in high-mobility scenarios.
• The paper highlights significant implications for enhancing V2X communications by enabling robust connectivity and safety improvements necessary for the transition toward fully autonomous vehicles.

Evolution of Radio Access Technologies for V2X Communications: IEEE 802.11bd and 5G NR V2X

The paper "IEEE 802.11bd and 5G NR V2X: Evolution of Radio Access Technologies for V2X Communications" provides an extensive analysis of the ongoing advancements in radio access technologies (RATs) tailored for Vehicle-to-Everything (V2X) communication, with a keen focus on the shift from existing paradigms—Dedicated Short Range Communications (DSRC) and Cellular V2X (C-V2X)—towards their evolutionary successors, IEEE 802.11bd and NR V2X. These technologies aim to address the stringent requirements of emerging vehicular applications which necessitate high reliability, low latency, and substantial throughput capabilities, essential in paving the way towards fully autonomous vehicles.

Overview

The current V2X communication technologies, DSRC and C-V2X, though competent in supporting elementary vehicular applications, fall short in meeting the demands of advanced autonomous vehicle applications due to limitations in scalability, intermittency under high-mobility scenarios, and the inability to guarantee the quality of service (QoS) needed for emerging applications. The paper delineates the enhancements being made to these technologies, presenting IEEE 802.11bd as an evolution of DSRC and NR V2X as the progression from C-V2X.

Evolutionary Objectives and Approaches

IEEE 802.11bd aims to augment the capabilities of the aging 802.11p standard by incorporating advanced PHY and MAC techniques introduced in subsequent Wi-Fi standards. Key objectives include doubling the throughput, extending the communication range, and maintaining backward compatibility with 802.11p. The incorporation of midambles, LDPC coding, and multi-antenna technology are expected enhancements to address channel estimation challenges in high-mobility environments.

NR V2X, built on 5G New Radio foundations, diverges significantly from C-V2X by embracing flexible numerologies and novel scheduling techniques like slot, mini-slot, and multi-slot scheduling. This evolution focuses not only on enhancing support for advanced vehicular applications through higher-order modulation schemes and robust sidelink channels but also introduces unicast and groupcast communication types.

Contrast and Comparisons

The developments in these technologies, albeit sharing common goals, take distinct paths in their execution. IEEE 802.11bd places emphasis on backward compatibility and interoperability with its predecessor, ensuring a seamless transition. Conversely, NR V2X does not impose backward compatibility constraints, thus allowing for a more radical redesign, better aligned with future-proof V2X applications. This lack of backward compatibility is counterbalanced by anticipated simultaneous deployments of NR and C-V2X by equipping vehicles with dual systems.

Performance Insights

Preliminary projections suggest that both evolutionary technologies promise substantial performance gains. For instance, NR V2X's exploitation of higher sub-carrier spacings improves both latency and reliability significantly compared to C-V2X. IEEE 802.11bd predicts advancements in throughput efficiency by leveraging midambles for effective channel estimation, facilitating higher order MCS usage.

Implications and Future Directions

The implications are profound as these technologies move towards standardization and eventual deployment. Practically, these evolutions are positioned to radically enhance vehicular communications, operating under complex mobility and density conditions inherent to future transportation systems. Theoretically, these shifts offer a fertile ground for further research in RAT optimizations, application-layer protocols, and integration strategies with other smart transportation technologies.

The paper also anticipates prevalent challenges, such as the coexistence of these evolving RATs with each other and with legacy systems, which necessitates astute spectrum management and interoperability strategies. These considerations are vital to realize an efficient, safe, and fully-integrated vehicular communication ecosystem.

In conclusion, the paper presented an insightful resource on the advancements in V2X communication technologies, noting significant contributions to understanding the evolutionary trajectories of IEEE 802.11bd and NR V2X. The proposed advancements, coupled with robust theoretical projections, hold promise for influencing future developments in V2X technology standards and implementations.