• Start with a small network with a lesser number of devices, say 1 gNB and 1 UE, and a Wired Node that can act as a server. Start with traffic generated from tools such as IPerf/JPerf and even from Wireshark PCAP logs which can be provided as input to NetSim. Scale the network and input traffic rate in steps. Keep in mind that NetSim needs to catch up with wall clock time in case of emulation mode.
• Limitations: NetSim emulator is an IP-based, data plane, flow-through emulator. It can emulate data plane functionality and not control plane functionality. NetSim source codes cannot be ported to hardware directly.

First, you'll need to map the virtual remote server to a real PC or virtual machine (VM). This can be done by setting the real-virtual IP address mapping within NetSim.

Next, you'll need to map the UE, or user equipment, to a real PC or VM. This can be accomplished in a similar manner as mapping the remote server, by selecting another PC or VM .

To emulate a data download, you can send a file from the PC/VM that is mapped to the virtual remote server (PC1) to the PC/VM that is mapped to the UE (PC2). This will allow the data to "virtually" flow through the 5G network within NetSim.

You can then measure various metrics such as throughput and delay by altering the properties of the gNB, or base station, within the NetSim scenario. This will allow you to analyze the performance of the 5G network under different conditions.

How do the network impairments work? Can we add impairments in Network/Transport/MAC layers? Or are there only PHY impairments due to pathloss models and data rate selection?

NetSim's wireless libraries can simulate various network impairments, such as packet loss and delay/jitter, that can negatively impact the performance of wireless communication systems. These impairments also affect network throughput.

The transport and network layers in NetSim rely on the PHY and MAC layers to provide a stable connection but can be affected by these impairments. Since NetSim simulates protocols in all layers of the stack, it is PHY/MAC impairments can cause problems at the network, transport, and application layers. These impairments cannot be directly set at the network/transport layers because doing so would result in the loss of all MAC/PHY details. Therefore, impairments impact in the following way.

At the transport layer: In NetSim, a packet or TCP ACK can fail due to MAC layer collision or PHY layer error, leading to issues such as packet re-ordering at the receiver, packet re-transmissions by the source, a drop in the TCP window, and reduced throughput.

At the network layer: In a large network simulation in NetSim, route tables can be affected if network layer control packets fail due to link errors caused by PHY/MAC impairments.