Multi-Cell, Multi-Channel URLLC with Probabilistic Per-Packet Real-Time Guarantee

Consider a wireless network where each communication link has transmission reliability and real-time guarantee. Certain pairs of wireless links interfere with each others and this interference is modeled by a interference model which enable predictable link reliability. Given the conflict graph and link QoS requirements, the objective is to determine whether and how the demands of all links can be satisfied. Prior studies have considered probabilistic per-packet real-time guarantees for single-cell, single-channel networks with implicit deadline constraints, but they have not considered real-world complexities such as inter-cell interference and multiple communication channels. Towards ensuring URLLC in multi-cell, multi-channel wireless networks, we propose a real-time scheduling algorithm based on \emph{local-deadline-partition (LDP)}. The LDP algorithm is suitable for distributed implementation, and it ensures probabilistic per-packet real-time guarantee for multi-cell, multi-channel networks with general deadline constraints. We also address the associated challenge of the schedulability test of URLLC traffic. In particular, we propose the concept of \emph{feasible set} and identify a closed-form sufficient condition for the schedulability of URLLC traffic. We propose a distributed algorithm for the schedulability test, and the algorithm includes a procedure for finding the minimum sum work density of feasible sets which is of interest by itself. We also identify a necessary condition for the schedulability of URLLC traffic, and use numerical studies to understand a lower bound on the approximation ratio of the LDP algorithm. We experimentally study the properties of the LDP algorithm and observe that the URLLC traffic supportable by the LDP algorithm is significantly higher than that of a state-of-the-art algorithm.