Impact of the DMRS Pattern on NR V2X Sidelink Communications

The 5G New Radio (NR) Vehicle-to-Everything (V2X) Sidelink (SL) standard defines multiple DeModulation Reference Signal (DMRS) patterns to support direct vehicular communications in high mobility scenarios. The DMRS pattern is a pre-defined sequence of signals that can be adapted for the transmission of each Transport Block (TB), and is used to estimate the channel response and mitigate the impact of the Doppler shifts experienced by the received signal in high relative speed conditions. The standard defines multiple DMRS patterns, but it does not provide any recommendations to indicate when each pattern should be used. To this end, this study presents an exhaustive analysis of the impact that the DMRS patterns have on the link level performance of NR V2X SL communications, deriving the first set of NR V2X SL recommendations on the DMRS pattern selection. The recommendations identify the maximum Modulation and Coding Scheme (MCS) that can be supported by each DMRS pattern to ensure high reliability levels, and cover different relative speeds, propagation scenarios, and number of subchannels. We also openly release the link level results generated and analysed in this study to derive the recommendations. To the authors’ knowledge, the obtained results represent the largest NR V2X SL link level dataset openly available.