Characterizing the Scheduling Performance of 5G NR Base Stations Under Signaling and Data Traffic Constraints

Aimed at rate-greedy applications having extreme requirements for the data rate at the air interface, 5 G New Radio (NR) systems may experience problems when the number of user equipment (UE) in the coverage of the cell increases due to limited capacity of the physical downlink control channel (PDCCH). The aim of this study is to explore the trade-off between the use of resources in the PDCCH channel utilized to inform UEs about their resource allocations in the cell and the physical downlink shared channel (PDSCH) utilized to carry user traffic demands. To this end, by utilizing stochastic geometry and probability theory, we develop models for different primary resource blocks (PRB) scheduling strategies. Then, relying on the tools of queuing theory, we formulate a model that jointly captures the UE requirements for both channels and characterizes the dynamics of the UE service process at the 5 G NR base station. Our results demonstrate that for non-sequential PRB scheduling, the PDCCH channel is the major bottleneck, whereas for sequential scheduling, PDSCH resources lead to missing scheduling opportunities. The long tail of the distribution of the amount of PRBs required for sequential PRB scheduling results in underutilization of the PDCCH channel. A much smaller tail in the case of non-sequential scheduling may allow improving it, but it requires careful tuning of the ratio between PDCCH and PDSCH resources. The proposed model allows us to determine this ratio as a function of user traffic demands, such that missing scheduling opportunities are minimized, while resource utilization is maximized. © 1967-2012 IEEE.