Applicable versionsNetSim StandardNetsim Pro

 

Applicable Releases
v13.3
v14.0


In a 5G network, the User Equipments (UE) such as 5G smartphones connect over the 5G RAN to a base station or gNB. This in turn connects to the 5G core which connects out to the Data Network (DN) like the Internet. The remote server is located in the DN. The UE downloads data - say a streaming video file from YouTube - from this remote server. Our goal is to obtain the SINR, MCS, and Throughput of the UE over time when the radio channel between the gNB and UE is time-varying. 


The figure below illustrates this scenario. We have a single UE at a distance of 750m from the gNB.  It downloads data from a server on the DN.  Time variations in the radio channel between the gNB and the UE are modeled by enabling fast fading. 

                                                

Fig 1: Scenario to be simulated 


The signal-to-noise ratio or SNR (which equals SINR in this case since we have no interference) depends on the pathloss between the gNB and the UE. The mean pathloss is modeled using the log distance model. The variation is pathloss is modeled using rayleigh fading. 


Next, the Modulation and Coding Scheme (MCS) defines the number of useful bits which can be carried by one symbol. MCS depends on radio signal quality or SINR in the wireless link. Higher the SINR higher the MCS and the more useful bits can be transmitted in a symbol. Clearly, a better MCS means higher throughput. 


How to model such a 5G network in NetSim?


Open NetSim and click New Simulation > 5GNR.

  1. Create a Scenario in 5GNR as shown in Fig 1 below.
  2. Drop 1 gnB and 1UE with 750m apart.
  3. Configure the CBR DL traffic from the server to UE at UDP full buffer.
  4. Enable LTENR_Radio_Measurement log file from logs in NetSim GUI.
  5. Enable plots in NetSim GUI.
  6. Run the simulation for 10 seconds.

Fig 2: The scenario shown in Fig 1 is created in NetSim. A 5G network scenario with a Single UE connected to a gNB which is connected to the 5G Core and the UE downloads data from the Server (Wired Node). The download rate from the server to the UE is such that the bottleneck link is the gNB-UE link. Hence the flow is "full buffer" at the gNB downlink. 


Attached herewith is an experiment file associated with this network configuration, which can be downloaded and imported in NetSim. 

 

gNB Interface 5G RAN properties

CA configuration

n78

Numerology

1

Channel Bandwidth

40 MHz

Tx Antenna Count

1

Rx Antenna Count

1

MCS Table

QAM256

CQI Table

TABLE2

PathLoss Model

Log Distance

PathLoss Exponent (η)

3

Reference Distance (D0)

1

Fading and Beamforming

Rayleigh with Eigen Beamforming

Coherence Time (ms)

10

UE properties

Tx Antenna Count

1

Rx Antenna Count

1

 

Results


The time-averaged Application Throughput can be obtained from the Throughput column in the application metrics of the NetSim Results dashboard. 

SNR vs. Time and MCS vs. Time graphs can be plotted from the LTENR_Radio_Measurement log file. The CBR Throughput vs. Time graph is directly plotted by enabling plots in NetSim GUI.



We can get SNR and MCS vs. time from LTENR_Radio_Measurement Excel log file. The steps to plot the graph are as follows:

  1. Filter the channel column to PDSCH because the network has downlink traffic.
  2. Select the Time (ms) column and SNR (dB) column from the excel sheet and click on the insert option from the toolbar.
  3. From the Insert option click on charts > scatter with smooth line option to get SNR vs. Time plot. Similarly, we can plot MCS vs. Time plot.



 

PLOTS:





 


Useful links


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

2. NetSim 5G documentation (v14.0): https://www.tetcos.com/downloads/v14/5G-NR.pdf

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