Successive Interference Cancellation-Aided NOMA in URLLC with Time and Frequency Diversity

Ultra-Reliable Low-Latency Communication (URLLC), contemplated in the Fifth-Generation New Radio (5G NR) standard, is considered essential to a broader implementation of latency-sensitive future technologies. Grant-Free (GF) schemes have been proposed towards reducing latency in URLLC, but the increased probability of collision conflicts with the reliability requirement. Aiming at reducing the impact of collisions, a transmission scheme using Non-Orthogonal Multiple Access (NOMA) and Successive Interference Cancellation (SIC), along with time and frequency diversity, is studied in this paper. Our results indicate that the proposed scheme considerably improves the system performance when compared to the destructive collision model commonly adopted in literature.