Risk-Aware Grant-Free for B5G/6G Ultra-Reliable Low-Latency Communications

Abstract

The fifth generation (5G) of mobile communication has been rapidly deployed during the last five years, and interest in this novel ecosystem is still increasing around the world. Nevertheless, several limitations have been identified due to a few novel use cases (e.g., VR/AR/XR, tactile internet, autonomous driving, telepresence, etc.) and the growing need for ubiquitous connectivity. 5G limitations have been leading the research community and industry to make notable progress in exploring new enabling technologies and envisioning the next generation of mobile communications networks. 6G is expected to deliver never-seen performance in terms of throughput (Tbits/s), latency (100 us), reliability, and global 3D connectivity. This way, 6G will transcend the Internet of Things (IoT) to the Internet of Everything (IoE) by supporting ubiquitous wireless access. In this paper, we intend to assess the applicability of a 5G and beyond Radio Access Network in terms of end-to-end latency, using an M/M/C queueing model. Specifically, we target Ultra-Reliable Low-Latency Communications (URLLC) applications and consider Grant-Free (GF) access schemes. Then, using the Conditional Value at Risk (CVaR), we derive an expression for the average violation delay given a target delay and reliability requirement. Finally, extensive simulations are performed to assess the accuracy and applicability of the derived model.