Flexible Multiplexing of Grant-Free URLLC and eMBB in Uplink

The fifth-generation wireless systems shall serve the traffic of various applications that impose different Quality of Service (QoS) requirements. A significant problem is how to efficiently multiplex flows with different QoS requirements having a limited amount of channel resources. In this paper, we study the problem of multiplexing enhanced Mobile Broadband (eMBB) traffic and Ultra-Reliable Low-Latency Communications (URLLC) traffic in the uplink channel. While the eMBB traffic is served with scheduled (grant-based) access to maximize throughput, the URLLC traffic is served with grant-free access to satisfy strict latency requirements. We propose a novel flexible scheme for eMBB/URLLC multiplexing that is based on non-orthogonal multiple access. As a part of this scheme, we develop a scheduling and power allocation algorithm for eMBB users that considers the constraints imposed by grant-free URLLC transmissions. With simulations, we compare the performance of the proposed scheme with the existing ones and show that our scheme increases throughput for the eMBB users while satisfying strict QoS requirements for the URLLC ones. Additionally, we demonstrate that the proposed scheme significantly reduces the protocol overhead induced by reconfiguration of grant-free URLLC transmissions, which is very important in the case of mobile URLLC users.