Opportunistic Spatial Preemptive Scheduling for URLLC and eMBB Coexistence in Multi-User 5G Networks

The fifth generation (5G) of the mobile networks is envisioned to feature two major service classes: ultra-reliable low-latency communications (URLLC) and enhanced mobile broadband (eMBB). URLLC applications require a stringent one-way radio latency of 1 ms with 99.999% success probability while eMBB services demand extreme data rates. The coexistence of the URLLC and eMBB quality of service (QoS) on the same radio spectrum leads to a challenging scheduling optimization problem, that is vastly different from that of the current cellular technology. This calls for the novel scheduling solutions which cross-optimize the system performance on a user-centric, instead of network-centric basis. In this paper, a null-space-based spatial preemptive scheduler for joint URLLC and eMBB traffic is proposed for the densely populated 5G networks. Proposed scheduler framework seeks for cross-objective optimization, where the critical URLLC QoS is guaranteed while extracting the maximum possible eMBB ergodic capacity. It utilizes the system spatial degrees of freedom in order to instantly offer an interference-free subspace for the critical URLLC traffic. Thus, a sufficient URLLC decoding ability is always preserved, and with the minimal impact on the eMBB performance. Analytical analysis and extensive system level simulations are conducted to evaluate the performance of the proposed scheduler against the state-of-the-art scheduler proposals from industry and academia. Simulation results show that the proposed scheduler offers extremely robust URLLC latency performance with a significantly improved ergodic capacity.