Study of 3GPP-based V2X Technologies

Background

C-V2X is a V2X communications technology developed by the 3GPP and standardized in 2017 in its Rel. 14 specifications. Building atop the cellular LTE, C-V2X leverages the widespread cellular infrastructure wherever available. Moreover, to make C-V2X suitable for high-speed vehicular environments, 3GPP introduced many features in its Rel. 14.

V2X concept

Since cellular infrastructure cannot always be relied upon, for example, along rural highways, 3GPP has defined an autonomous resource reservation algorithm, which enables C-V2X equipped vehicles to communicate even when they are out-of-coverage. Together, these features in C-V2X are likely to enable day-1 vehicular safety applications such as left turn assist, emergency electronic brake lights, blind spot warning, etc.

To further enhance the performance of C-V2X and to provision support for advanced vehicular applications, 3GPP developed the New Radio V2X (NR V2X) in its Rel. 16 specifications. NR V2X builds on top of the 5G New Radio, thereby leveraging all new features and mechanisms introduced in 5G NR. As such, the 5G NR V2X is a major overhaul over it's predecessor C-V2X. NR V2X is undergoing design in a forward compatible fashion. This implies that future releases of 3GPP-based V2X technologies can be easily integrated with 5G NR V2X.

In this project, we look at several issues surrounding the performance of C-V2X, especially in the sidelink mode 4, i.e. scenarios where C-V2X-equipped vehicles operate outside cellular coverage.

External Resources

Introductory Videos



Introductory Papers

  • An Overview of 3GPP Cellular Vehicle-to-Everything Standards
    [Open Access]
  • IEEE 802.11bd & 5G NR V2X: Evolution of Radio Access Technologies for V2X Communications
    [Open Access]
  • Survey and Perspectives of Vehicular Wi-Fi versus Sidelink Cellular-V2X in the 5G Era
    [Open Access]
  • LTE-V for Sidelink 5G V2X Vehicular Communications: A New 5G Technology for Short-Range Vehicle-to-Everything Communications
    [IEEE Xplore | Open Access]
  • Analytical models of the performance of C-V2X mode 4 vehicular communications
    [IEEE Xplore | Open Access]
  • Study of the Impact of PHY and MAC Parameters in 3GPP C-V2V Mode 4
    [IEEE Xplore | Open Access]
  • On the Performance of IEEE 802.11p and LTE-V2V for the Cooperative Awareness of Connected Vehicles
    [IEEE Xplore | Open Access]

Our Contributions

  • We developed an ns-3 simulator that simulates the physical and medium access control layers of C-V2X sidelink mode 4.
  • Using this simulator, we studied the performance of C-V2X in various scenarios, i.e. urban/highway and low load/high load scenarios.
  • We also studied the impact of co-channel and adjacent-channel Wi-Fi transmissions on C-V2X performance.

Publications

  • The 3rd Generation Partnership Project (3GPP) is actively designing New Radio Vehicle-to-Everything (NR V2X)— a 5G NR-based technology for V2X communications. NR V2X, along with its predecessor Cellular V2X (C-V2X), is set to enable low-latency and high-reliability communications in high-speed and dense vehicular environments. A key reliability-enhancing mechanism that is available in C-V2X and is likely to be re- used in NR V2X is packet re-transmissions. In this paper, using a systematic and extensive simulation study, we investigate the impact of this feature on the system performance of C-V2X. We show that statically configuring vehicles to always disable or enable packet re-transmissions either fails to extract the full potential of this feature or leads to performance degradation due to increased channel congestion. Motivated by this, we propose and evaluate Channel Congestion-based Re-transmission Control (C2RC), which, based on the observed channel congestion, allows vehicles to autonomously decide whether or not to use packet re-transmissions without any role of the cellular infrastructure. Using our proposed mechanism, C-V2X-capable vehicles can boost their performance in lightly-loaded environments, while not compromising on performance in denser conditions.


    [Download | IEEE Xplore | Slides]

  • With the 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 survey the latest developments in the standardization of 802.11bd and NR V2X. We begin with a brief description of the two present-day vehicular RATs. In doing so, we highlight their inability to guarantee the 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.


    [Download | arXiv | IEEE Xplore]

  • The 5.9 GHz band has been earmarked in many countries for Intelligent Transportation Systems (ITS) applications. Cellular V2X (C-V2X)—a recently developed access technology for vehicle-to-everything (V2X) communications—is a candidate technology to provision ITS applications using the 5.9 GHz band. Due to the ever-increasing popularity of Wi-Fi and search for additional unlicensed bands, in the US and Europe, regional regulators have previously considered allowing co-channel Wi-Fi operations in the ITS band on a secondary basis to the incumbent ITS technology. Additionally, there are several Wi-Fi channel configurations, some already in operation while others still under consideration, which place Wi-Fi and C-V2X devices in adjacent bands. It is, therefore, likely that C-V2X users may be susceptible to interference from Wi-Fi devices operating both in co-channel scenarios and in adjacent bands. To make an informed decision on future Wi-Fi channelization in and around the ITS band, a detailed study on the impact of these Wi-Fi transmissions on the system performance of C-V2X is extremely essential. In this paper, through a comprehensive and systematic simulation study, we investigate the impact of Wi-Fi transmissions on the performance of C-V2X, both in co-channel and adjacent channel scenarios. Our simulations reveal that if Wi-Fi devices are to coexist with C-V2X in the same spectrum, existing mechanisms either fall short of sufficiently protecting C-V2X performance or render the spectrum unusable for Wi-Fi operations. On the other hand, all Wi-Fi channels that are adja- cent to the ITS band can significantly degrade the system-wide C-V2X performance. In such scenarios, to adequately protect the C-V2X network performance, either certain restrictions need to be put in place on Wi-Fi operations, or the operations of Wi-Fi in such channels must be prohibited.


    [Download | IEEE Xplore | Slides]

Videos