Overcoming Directional Deafness in High Frequency Sidelink Communications

Device-to-device (D2D) communication using SG New Radio (NR) sidelink (SL) is envisioned to be a key enabler of high speed, low latency applications, with automated driving being the prime use case. To meet the high data rate requirements, it is essential for SL devices to be able to operate in mmWave/sub-THz frequencies where bandwidth is abundant. Consequently, several enhancements will be needed to the current version of NR SL, which is mainly designed for sub-6 GHz frequencies. Beamforming based highly directional transmission/reception used at high carrier frequencies result in directional deafness in other directions. For SL UE autonomous resource allocation, termed as Mode 2 of NR SL in 3GPP, this results in a UE's inability to detect transmissions not aligned to its primary direction of reception, which leads to high packet errors. In this paper, we focus on system wide performance of 3GPP based NR SL Mode 2 resource allocation for directional systems at mmWave/sub-THz frequencies. We propose a composite strategy that comprises paired SL control transmission and sensing, whereby SL UEs transmit and receive the SL control information in an additional "paired" direction, directly opposite to their intended direction of transmission. This helps eliminate hidden node interference while avoiding too many exposed nodes. System level simulations in NR V2X highway scenarios show significant performance improvement of the proposed scheme over conventional solutions like omnidirectional or directional transmission/reception of SL control information.