5G Sidelink Positioning in 3GPP Release 18 and Release 19

New Radio (NR) sidelink (SL) positioning has been introduced in the Third Generation Partnership Project (3GPP) Release 18 to enhance NR SL communication that has been developed since 3GPP Release 16. SL positioning is used to determine the user equipment’s (UE) position to support use cases such as Vehicle-to-Everything (V2X) communications, public safety, commercial use-case and Industrial Internet of Things (IIoT). The design of SL positioning requires integration into the existing framework of the NR SL communication. A novel sequence to generate SL-positioning reference signal (SL-PRS) needed to be defined. Besides that, resource pools, resource allocation, time and frequency domain patterns also required standardization to avoid collisions between the SL-PRS transmissions and the legacy NR SL transmissions. There is strong support to extend SL positioning to unlicensed spectrum (SL-U) in Release 19. This article provides a detailed overview of the physical layer design of Rel-18 NR SL positioning and addresses some of the challenges for SL-U positioning in Release 19.