5G K-SimSys for Open/Modular/Flexible System-Level Simulation: Overview and its Application to Evaluation of 5G Massive MIMO

5G K-SimSys is a system-level simulator which has been designed and implemented to provide an open platform and a tractable testbed for evaluating the system-level performance of 5G standard. In this paper, we present its design overview with the overall modular structure, including the functionality of the flexible modules. Meanwhile, massive multi-input multi-output (MIMO) is a key technology for improving the spectral efficiency of 5G systems. While massive MIMO has been standardized in 3GPP Rel-13 (LTE-Advanced Pro), the next generation of massive MIMO standard is now available in Rel-16, a.k.a New Radio (NR) interface, with further improvement by introducing more antenna elements over the higher frequency band. In particular, the beam-based air interface for above 6 GHz band involves various antenna configurations and feedback schemes, requiring a more complex testbed for system-level performance evaluation. This paper examines the multi-antenna technologies in 3GPP NR specification to develop its system-level model in 5G K-SimSys in order to test the factors affecting performance in the corresponding environments through various embodiments. In the simulation results, the baseline performance for massive MIMO in NR is evaluated by changing the number of antenna ports and the number of spatial multiplexing layers in different experimental environments. Particularly, the effect of vertical beamforming on interference is evaluated for Full Dimension MIMO (FD-MIMO). In order to demonstrate that 5G K-SimSys is an easy-to-design simulator that facilitates modification and reconfiguration, owing to its modularized and customized structure, we consider the proposed bandwise analog beamforming (BAB) scheme. The modular and flexible structure immediately allows implementation of virtual modules for bandwise analog beamforming by reusing the elementary modules as hierarchically designed simulator objects.