3GPP NR V2X Mode 2: Overview, Models and System-Level Evaluation.

Following the successful use of sidelink in Long Term Evolution (LTE) for Proximity Services (ProSe) and Cellular Vehicular-to-everything (C-V2X), the 3rd Generation Partnership Project (3GPP) is working towards its evolution in New Radio (NR) systems in the context of the so-called NR V2X. This new technology is expected to complement LTE C-V2X for advanced services by offering low latency, high reliability, and high throughput V2X services for advanced driving use cases. To do this, NR V2X is equipped with new features, such as the support for groupcast and unicast communication, a novel feedback channel, and a new control channel design. In this paper, we provide a complete history of sidelink technology in 3GPP followed by a detailed overview of NR V2X technology, with special emphasis on Mode 2 for out of coverage operation and autonomous resource selection. Furthermore, this paper presents a system-level NR V2X standard-compliant simulator, as an extension of the popular and open-source NR network simulator 5G-LENA, based on ns-3. In particular, we focus on the design, implementation, and evaluation of the sensing-based resource selection in NR V2X Mode 2, in a highway scenario. Through several and extensive simulation campaigns, we test the impact of different NR V2X parameters, such as the numerology, the resource selection window size, the number of retransmissions, the maximum number of resources per reservation, and the probability of keeping the same resources during reselection, in a sensing-based resource selection. Finally, we provide a comparison campaign that shows the gains attained by the sensing-based resource selection, proposed during 3GPP Release 16, over the random selection strategy, considered in 3GPP Release 17 for power saving purposes.