**Channel modelling for millimeter wave 5G communication:**

In general, we employ 1. analytical channel modelling; 2. map based channel modelling; and 3. sinusoidal channel modelling for wireless communication channel modelling. Analytical modelling is based on measurements such as pathloss, rms delay spread, and so on. Map-based channel modelling, on the other hand, is focused on the geographical architecture of a specific location. When we derive a channel model for a specific frequency band, we use these two models. We'll focus on channel modelling for millimetre wave communication, which is a promising contender for enabling 5G communications.

When interacting with metal, glass, and other surfaces, mm Wave signals have a higher reflectivity and are more easily absorbed by air, rain, and other elements than signals in lower frequency bands. Furthermore, its diffraction ability is reduced. As we aforementioned channel modelling approaches fall into one of three categories: analytical modelling, map-based modelling, and stochastic modelling. Analytical modelling uses a set of established parameters, whereas ray-tracing-based modelling focuses on locating signal paths in the environment. For applications such as massive MIMO and enhanced beam formation, the map-based model delivers precise and realistic spatial channel features.

**Analytical Channel Modelling:**

The appropriate statistical parameters such as number of pathways, root-mean-square (RMS) delay spread, path loss, and shadowing of the propagation channel can be produced using the analytical modelling approach, which is based on the data of measurements or statistical characteristics of the scenario. Without taking into account the specifics of the environment, this method can be represented using a given set of parameters. As a result, in an anisotropic radio environment, the analysis result may be inaccurate.

**Map-based Channel Modelling:**

For applications such as massive MIMO and sophisticated beamforming, the map-based model delivers precise and realistic spatial channel features. It automatically generates spatially consistent modelling for difficult instances like D2D and V2V links with dual-end mobility. Ray tracing is used in conjunction with a reduced 3D geometric description of the propagation environment to create the model. Diffraction, specular reflection, diffuse scattering, and blocking are all considered important propagation mechanisms. The electromagnetic material properties of building walls are modelled as rectangular surfaces. There is no explicit path loss model in the map-based model. Instead, path loss, shadowing, and other propagation features are defined by the map layout and, optionally, a random distribution of objects that account for people, automobiles, and trees, among other things.

**General description:**

A geometrical representation of the environment – such as a map or a building layout expressed in a three-dimensional (3D) Cartesian coordinate system – is required for any ray-tracing-based model. It is not necessary to have a high level of map detail. Building walls and potentially other fixed structures are the only things that need to be defined.

Here in the above figure signal reaches to cell phone via MPCs where paths are either reflected or reflected. The probability of LOS path decreases as operating frequency increases.

**Creation of the environment:**

When walls are modelled as rectangular surfaces, a 3D map comprising coordinate points of wall corners is constructed. Both outside and indoor maps, as well as the position of indoor walls within a building block, are defined in the outdoor-to-indoor instance. The map is then strewn with random scattering/shadowing objects that depict persons, automobiles, and other items. The item positions can then be defined either based on a known regular pattern, such as the spectator seats in a stadium, or randomly selected from a uniform distribution with a set situation dependent density.

**Determination of propagation pathways:**

Direct, diffraction, specular reflection, and diffuse scattering must all be represented for this purpose, as seen in Figure above. The diffuse scattering caused by rough surfaces is compensated for by placing point scatterers on the external walls' surface.

Here in millimeter wave channel modelling map-based channel modeling is very important because here types of obstacle's surfaces, constructional architecture of a area, angle of arrival and departure (AoA and AoD) matters a lot.

**Stochastic Channel Modelling:**

The stochastic model is based on the Geometry-based Stochastic Channel Models (GSCMs) family, which includes 3GPP 3D Channel Models. It concentrates on path loss, the sum-of-sinusoids approach for calculating large-scale parameters, and so on.