A fifth-generation system (5G) mobile networks has been developed to realize high throughput, low latency, high scalability, the provision of ubiquitous connectivity solution for end-users, and efficient energy consumption technique. The benefits of 5G New Radio (NR) access technology in the physical layer design accommodate to be flexible and scalable that can support many use cases such as orthogonal frequency division multiple access (OFDMA) at its medium access control (MAC) layer and numerology. The efficiency of OFDMA depends on how the access point (AP) schedules channel resources among STAs (stations). The common schedulers used in OFDMA are round - robin (RR), maximum rate (MR), and proportional fair (PF). This study evaluates the downlink access with varying scheduling mechanisms, the number of user equipment (UE), and numerology with an additional proposed scheduler mechanism called Optimized PF to maintain high throughput and fairness using 5G-NR LENA (LTE/EPC Network Simulator) module in the ns-3 environment. Based on the study, the RR scheduler has stable packet delivery performance from numerology 0 and 4 which can still send packets to all UEs. It caused the RR scheduler does not use a channel quality indicator (CQI) to discriminate the user and the used scenario uses the same data rate for every UEs. Besides, the additional scheduler mechanism, optimized PF, performs better than the PF scheduler for sending packets in numerology 4 (higher numerology). Also, increasing numerology will result in increasing the mean throughput and packet delivery ratio for each scheduler.