System Level Analysis of K-Repetition for Uplink Grant-Free URLLC in 5G NR

Ultra-reliable low-latency communications (URLLC) sets high service requirements for the fifth generation (5G) new radio (NR) standard. Grant-free (GF) transmissions is considered a promising technique for reducing the latency in the uplink. To achieve efficient radio resources utilization, sharing of resources is required for sporadic uplink traffic. Repetitions based transmission schemes aims to enhance the reliability of GF transmissions. However, repetitions may also generate excessive interference and cause additional queuing, harming the reliability and latency. In this work, we explore radio resource management (RRM) configurations for repetition based transmission schemes. That includes the number of repetitions, the allocation size per transmission (sub-band), sub-band hopping and uplink power control. Evaluations are conducted in a 5G NR compliant multi-user multi-cell simulation scenario with sporadic uplink GF URLLC transmissions. Our findings suggest that repetitions based schemes can, with a careful selection of the sub-band size and uplink power control parameters, achieve comparable URLLC performance with retransmission based schemes when the effect of queuing is disregarded.