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All the propagation models in NetSim are statistical in nature.

In a deterministic propagation model, specific parameters such as terrain, foliage, walls, building geometry & floor plans, antenna patterns, etc. are considered apart from the exact transmitter and receiver positions. In many cases, the material and physical properties of these objects are also taken into account. The propagation algorithms include transmission, reflections, diffraction, and scattering of signals when they interact with surfaces and materials or pass through different mediums. Such detailed modeling can only be performed using specialized radio propagation software.

NetSim, is a full stack, end-to-end, packet-level, network simulator. It allows users to model the flow of traffic (data, voice, video, etc.) over the network. In contrast, RF propagation tools focus solely on signal propagation and do not model any data transmission. Attempting to perform both traffic simulation and detailed RF planning simultaneously is not computationally feasible. Therefore, NetSim, in alignment with industry standards, provides statistical models for its simulations.

In 5G, NetSim implements the statistical propagation models described in 3GPP TR 38.901. These include pathloss, shadow fading, LOS probability, and penetration losses. The specifics of the model and its implementation is explained in section 3.11 of the 5G technology library manual.

With NetSim, you have the flexibility to:
1. Choose between the Urban Macro or Urban Micro propagation model.
2. Define the Line-of-Sight (LOS) or Non-Line-of-Sight (NLOS) selection based on user requirements.
3. Select a suitable LOS probability, and
4. Introduce buildings to simulate indoor propagation and outdoor-to-indoor losses when the UE is "within" the building. 

With respect to the positioning of gNodeB (gNB) and User Equipment (UE), indoor or outdoor, NetSim automatically applies corresponding propagation models:

• Outdoor gNB to Outdoor UE: Outdoor PL model
• Outdoor gNB to Indoor UE: Outdoor PL till building, then penetration (O2I) loss, and finally indoor PL within the building
• Indoor gNB to Indoor UE: Indoor PL model
• An Indoor gNB cannot be connected to an Outdoor UE in NetSim

When a building is situated between an outdoor gNB and an outdoor UE, NetSim categorizes it as an Outdoor gNB to Outdoor UE scenario; the building doesn't induce any additional pathloss or shadowing or reduce LOS probability. This is because, to our understanding, the standard does not explicitly specify statistical formulas for pathloss, shadowing, and LOS probability in such cases. 

Another option is to simulate the path loss and shadowing separately using a suitable radio propagation tool. Once you have the path loss and shadowing data, you can import it into NetSim. During the simulation, NetSim will utilize this imported data instead of its built-in propagation models. This way, you can run traffic simulations in NetSim with more accurate propagation characteristics based on the external tool's output. 

• The pathloss file should start with the device name followed by “_Pathloss” and be saved as a text file (*.txt).
• The first two lines must include these parameters.

• The axis length represents the maximum distance up to which data points will be provided. The number of entries along X for example will be X-Axis-Length divided by X-Axis-Step-Length. 
• The pathloss does not vary between each point; it only changes at the "next" point, whose coordinates are determined by the step-length.
• Subsequently, x, y, and z coordinate with pathloss value must be given. 

• Here is an example of what this might look like:

• Please note that if the UE is placed or moves to a location beyond xmax or ymax, the pathloss will default to 500 dB. 
• If you provide an input file for an eNB/gNB, the system will calculate path loss according to that file. Without such a file, NetSim will use the standard pathloss models for calculation.

Useful links

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