3GPP NR Sidelink Transmissions Toward 5G V2X

Abstract

Featuring direct communications between two user equipments (UEs) without signal relay through a base station, 3GPP sidelink transmissions have manifested their crucial roles in the Long-Term Evolution (LTE) Advanced (LTE-A) for public safety and vehicle-to-everything (V2X) services. With this successful development in LTE-A, the evolution of sidelink transmissions continues in 3GPP New Radio (NR), which renders sidelink an inevitable component as well as downlink and uplink. Targeting at offering low latency, high reliability and high throughout V2X services for advanced driving use cases, a number of new sidelink functions not provided in the LTE-A are supported in NR, including the feedback channel, grant-free access, enhanced channel sensing procedure, and new control channel design. To fully comprehend these new functions, this paper therefore provides essential knowledge of 3GPP NR sidelink transmissions, including the physical layer structure, resource allocation mechanisms, resource sensing and selection procedures, synchronization, and quality-of-service (QoS) management. Furthermore, this paper also provides performance evaluation to assess the gains brought from the new control channel design. As NR sidelink transmissions have been regarded as a foundation to provide advanced services other than V2X in future releases (e.g., advanced relay), potential enhancements are also discussed to serve the urgent demand in corresponding normative works.

Performance Improvement for Multi-User Millimeter-Wave Massive MIMO Systems

“…The potential of the proposed solutions in this paper could demonstrate the potential increase in spectral efficiency for cellular vehicle-toeverything (C-V2X) communications. However, accurate vehicular data for simulations are required, and these studies should rely on the 3GPP release 16 specifications where the C-V2X communications standard is addressed [20], [44].…”

6G Cellular Networks and Connected Autonomous Vehicles

“…However, IEEE 802.11p suffers several limitations due to its primary use of random channel access, which include 1) lack of QoS guarantee, 2) unbounded delay at physical channels, 3) short-lived connectivity between vehicles and infrastructure, 4) a need to deploy IEEE 802.11p infrastructure at a large scale, etc. To overcome these limitations, the 3rd generation partnership project (3GPP) proposed cellular based V2X, namely, C-V2X, which utilizes existing cellular communication infrastructure for V2X [9], [10]. Unlike IEEE 802.11p, the cellular technologies have inherent QoS mechanisms and are well-known for the merit of mobility management.…”

“…The sidelink transmission for V2X was enhanced in 3GPP Release 15 with some new functions such as transmission diversity, carrier aggregation and higher quadrature amplitude modulation. The 3GPP Release 16 specifies 5G NR based V2X support with a few more new functions, including the support for unicast and multicast, which are particular useful for CAV applications, enhanced channel sensing, resource selection and QoS management schemes, and congestion control [9], [10]. 3GPP Release 17 is in its planning stage, which is expected to be completed in 2022, with further enhancement on the sidelink efficiency, URLLC and positioning, and use of relay and frequency range 2 (FR2) over 6 GHz.…”

An Explicit Reservation-Augmented Resource Allocation Scheme for C-V2X Sidelink Mode 4

“…Then the reservation information would not be accommodated in the Reserved field of the current SCI Format 1. As to the increased signaling bits required by GRaSPS, it is worthwhile to note that in 5G V2X, the SCI is split into two stages so that the second stage will be carried in the Physical Sidelink Shared Channel (PSSCH) instead [22], which will allow for more room in the SCI so that we can utilize more bits to specify explicitly reservation information. For instance, a recent proposal in the 3GPP Radio Access Network Working Group 1 (RAN1) is to move the RRI and the MCS fields among others to the SCI stage 2, making room for other new fields [23].…”