Airwaves wave propagation can be categorized as LOS

Airwaves wave propagation can be categorized as LOS (Line Of Sight) and non-LOS modalities. LOS is direct point-to-point distribution with no obstructions in between. Non-LOS might be indirect propagation in the absence of LOS path which consists of diffraction, expression and scattering. In the HF wedding ring (3 - 30 MHz), propagation is primarily using sky trend for long distance communications. VHF and UHF (30 MHz - 2 GHz) waves travel by LOS and ground bounce propagation. The SHF (3 to 30 GHz) wave uses strictly LOS propagation.

The goal of propagation modeling is to decide the probability of satisfactory functionality of a wireless system that depends on radio wave propagation. For RF systems planning, the modeling of propagation is for the purpose of RF protection analysis. This analysis uses the propagation model and terrain files to predict the RF protection area of a transmitter, the received signal strength at the end of a wireless link, the path loss from the transmitter into a distance receiver, the antenna lean angle of the transmitter, the bare minimum antenna height to establish Line of Sight communication path and channel impairment such as delay spread due to multi-path fading.

Propagation models for different software, environments and terrains had been developed by the US government, private organizations and regular body such as International Telecommunications Partnership (ITU). These models are based on massive amount empirical data collected for the purpose of characterizing propagation for that application. Since propagation models are created using statistical procedures, no single model will exactly fit in any particular application. It is a good plan to employ two or more independent models and use the results as bounds on the expected performance. The following are a list of most commonly used near-earth propagation models.

The Longley-Rice model predicts long term median tranny loss over irregular terrain. It can be designed for frequency from 20 Megahertz to 20 GHz and path time-span from 1 to 2000 Km. The model accounts for terrain, issues, subsoil conditions and ground curvity. Longley-Rice model has two modes, point-to-point and area. The point-to-point mode uses detail terrain files and characteristics to predict route loss, whereas the area mode makes use of general information about the terrain characteristics to predict path loss.

The Okumura model is based on the measurements produced in Tokyo in 1960, between two hundred to 1920 MHz. The assessed values are used to determine the median field strength and numerous correction variables. The correction factors include adjustment to the degree of urbanization, terrain roughness, base station antenna height, cellular antenna height and localized sign up here obstruction. The Okumura model is especially applied in urban area for standard coverage calculation where numerous interferences and buildings exist.

The Cost 231 Model, also called the Hata type PCS extension, is used in most industrial RF planning tools for mobile telephony. The coverage of the Cost 231 model is frequency between truck to 2000 MHz, transmitter valuable antenna height between 30 to 200 m, receiver effective antenna height between 1 to 12 m and link distance through 1 to 20 km. The Cost 231 model is restricted to application where base station antenna is above adjacent roof tops.

The Egli model is a simplified model according to empirical match of measured info to mathematical formula. Its ease of implementation makes it a popular choice for use in the initial analysis. It assumes gentle moving hill height of approximately 50 toes and no terrain elevation data between the transmitter and receiver is needed for the model. The median path damage is adjusted for the height associated with transmit and receive antenna previously mentioned ground. The model consists of a single equation for the propagation loss.

TERSEBUT terrain model is based on diffraction theory that provides a method to predict median way loss. The model predicts course loss as a function of the elevation of path blockage and the primary Fresnel zone for the transmission link. The model is ideal for modeling line-of-sight link in any terrain and is best for any frequency and path length of time. The model accounts for obstructions in the course of the communication link, hence it really is suitable to be used both inside metropolitan areas and open fields. The model is considered valid for losses above 15 dB.