Improving ultra-reliable low-latency communication in multiplexing with enhanced mobile broadband in grant-free resources

In uplink (UL) transmission, the Ultra-Reliable Low-Latency Communication (URLLC) users (UEs) might be assigned the grant-free (GF)/configuredgrant (CG) periodic resources to transmit data straightaway instead of sending scheduling request (SR) and receiving UL grant. However, when these resources are not in use by the URLLC traffic, the base station (called gNB) can dynamically schedule the Enhanced Mobile Broadband (eMBB) UEs to transmit in the GF resources to increase the resource efficiency. This may lead to potential collision and detrimental QoS for URLLC as some of the URLLC UEs may become active and try to use the same resource assigned to an eMBB UE. In this paper, a two-step strategy containing an overlap indication and explicit Hybrid automatic repeat request (HARQ) feedback is proposed to improve URLLC performance in multiplexing with eMBB. Besides the explicit HARQ feedback structure, a scheme with an additional SR is also presented. Simulation results show that these two schemes help achieving URLLC requirements by reducing error probability due to Demodulation Reference Signal (DMRS) miss-detection while allowing better resource efficiency.