Comp-Enabled URLLC Availability Analysis with NR Protocols

Ultra-reliable and low-latency communication (uRLLC) is an important feature for the fifth-generation mobile network and beyond (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{5 G} \boldsymbol{/} \mathbf{B 5 G}$</tex>). It has stringent requirements for ultra-high reliability (e.g., 1e-5) and extremely low user plane latency (e.g., 1ms). For cell edge user equipments (UEs) with severe inter-cell interference, uRLLC availability, i.e., defined as the probability of satisfying both reliability and latency requirements simultaneously, tends to be low. Under the constraint of 5G new radio (NR) protocols, in order to improve the availability of uRLLC, the bottleneck mainly lies in the guarantee of transmission reliability. Coordinated multi-point (CoMP) transmission is an enabling technique to improve the uRLLC availability via spatial diversity. This paper mainly focuses on the availability analysis of CoMP-enabled uRLLC with NR protocols. The uRLLC availability can be equivalent to a full probability model with the conditional probability of reliability given a latency constraint. Firstly, considering the NR frame structure and the procedure of the user plane processing with hybrid automatic repeat request (HARQ), a maximum transmission count is obtained given the latency requirement. Then, the system uRLLC availability is derived with the maximum transmission count for typical and edge UEs using stochastic geometry (SG). Finally, the analytical results are validated by Monte Carlo simulations. Moreover, the results show that in a single transmission, the system uRLLC availability with CoMP can be improved by 39.20 % for typical UEs and 322.44% for edge UEs compared with No-CoMP.