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NetSim users who are interested in approximate data rate values can use the formula

Data Rate = BW * Q * R * N * (1 - OH)

where BW is the bandwidth, Q is the modulation order, R is the code rate, N is the number of MIMO layers, and OH is the Overhead. Here, OH is usually taken as 2/14 i.e., 2 control symbols in a slot spanning 14 symbols. When operating in TDD mode, the above computation would give the two-way (downlink + uplink) data rate. Therefore the downlink data rate would be

DL-rate = Data Rate * DL-Fraction

While BW, OH, and N are fixed by used input in NetSim, Q and R are dependent on the modulation and coding scheme (MCS). Now, in 5G, the transmitter adapts its PHY layer MCS depending on the receiver's SINR. The SINR in turn depends on the received power, which is transmit-power less path loss.  

In NetSim users can record the radio measurements to obtain the SINR and MCS (for each UE) over time if the channel is time-varying.

Example: Let us say we have a case where

BW = 40 MHz

Receive SINR is such that MCS 13 is chosen 

For MCS 13, modulation is 64 QAM (Q = 6) and R = 567/1024

DL/UL ratio = 4:1 which implies DL Fraction = 4/5

Transmit antennas, Nt = Receive antennas, Nr = 1, and therefore number of MIMO layers = Min (Nt, Nr) = 1

Useful link

1. Overview of NetSim 5G library: https://tetcos.com/5g.html

2. NetSim 5G documentation (v13.3): https://www.tetcos.com/help/v13.3/Technology-Libraries/5G-NR.html