System-Level Evaluation of 5G NR UE-Based Relays

The notion of User Equipment (UE)-based relays started with the introduction of Proximity Services (ProSe) and Device-to-Device (D2D) direct communication over the Sidelink (SL), and evolved with the specification of the Fifth Generation (5G) New Radio (NR) interface. While the main goal of UE-based relays is to extend coverage, many parameters play a role in determining its effective range and benefits. In this paper, we study a military use case involving UE-to-Network (U2N) relays providing connectivity to a squad of soldiers with limited coverage. We configure advanced NR SL functionalities that include diverse numerologies, sensing-based resource selection, and blind retransmissions. We evaluate the end-to-end network performance in terms of Packet Delivery Ratio (PDR) and latency. We show, through system-level simulations, that fine-tuning the different NR SL parameters is critical to achieve the expected performance in scenarios where the relay UE is serving a variable number of UEs.