Resource Allocation for Uplink Grant-Free Ultra-Reliable and Low Latency Communications

Ultra-Reliable and Low Latency Communications (URLLC) is an important emerging area for the fifth generation (5G) cellular network. The requirements for URLLC are as stringent as 1−10-5 reliability for a 32-byte packet with user plane latency of 1 ms. To achieve these requirements, grant-free transmission with repetitions of data packet has been recently proposed for uplink transmissions. However, the resource overhead and collisions among URLLC user equipments (UEs) become limiting factors to achieving optimal system performance. In this work, a hybrid resource allocation scheme is proposed to optimally allocate dedicated resource units and/or a shared resource pool to a group of UEs. Numerical results based on theoretical analysis show that the target requirements of URLLC can be achieved with up to 70% reduction in resource utilization compared to the conservative transmission scheme.