Overcoming Directional Deafness in High Frequency Sidelink Communications

"5G new radio (NR) sidelink (SL) is envisioned as a key enabler of high speed, low latency applications like automated driving. To meet the high data rate requirements for such applications, SL support at mmWave and sub-THz frequencies with large bandwidths will be essential. Several enhancements and optimizations will be needed to the latest version of NR SL, which is mainly designed for sub-6 GHz frequencies. In this paper, we focus on UE autonomous resource allocation i.e., Mode 2 of the 5G NR SL, in the context of highly directional systems at mmWave and sub-THz frequencies. Inherent directionality at such high carrier frequencies leads to transmission and reception being limited to narrow pencil beams, resulting in directional deafness to other directions. For autonomous resource allocation in SL, this results in a SL UE’s inability to detect transmissions not aligned to its primary direction of reception. Such undetected transmissions may collide with the UE’s selected resource and cause packet errors. We propose a composite strategy which comprises of a paired SL control transmission and paired sensing, whereby SL UEs transmit and receive the 1st stage of SL control in an additional “paired” direction i.e., directly opposite to their intended direction of transmission. This helps in eliminating critical hidden node interference while avoiding too many exposed nodes. System level simulations are used to benchmark the performance of the proposed paired scheme against more conventional solutions like omnidirectional or directional transmission/ reception of SL control. Simulations for deployment scenarios, inspired from 5G NR indoor-office and NR V2X highway scenarios, show significant performance improvement of the proposed scheme over the legacy strategies."