The airwaves wave propagation can be

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

The goal of propagation modeling is to decide the probability of satisfactory overall performance of a wireless system that is determined by radio wave propagation. For RF systems planning, the modeling involving propagation is for the purpose of RF insurance analysis. This analysis uses the propagation model and terrain info to predict the RF policy area of a transmitter, the obtained signal strength at the end of a wireless url, the path loss from the transmitter into a distance receiver, the antenna click here lean angle of the transmitter, the bare minimum antenna height to establish Line of Eyesight communication path and channel impairment such as delay spread due to multi-path fading.

Propagation models for different programs, environments and terrains had been manufactured by the US government, private organizations and normal body such as International Telecommunications Association (ITU). These models are based on large amount of 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 any particular application. It is a good option to employ two or more independent models plus use the results as bounds in the expected performance. The following are a list of most commonly used near-earth propagation models.

The Longley-Rice model predicts long term median indication loss over irregular terrain. Its designed for frequency from 20 Megahertz to 20 GHz and path proportions from 1 to 2000 Km. The model accounts for terrain, environment, subsoil conditions and ground curvity. Longley-Rice model has two ways, point-to-point and area. The point-to-point mode uses detail terrain info and characteristics to predict course loss, whereas the area mode utilizes general information about the terrain characteristics to be able to predict path loss.

The Okumura model is based on the measurements produced in Tokyo in 1960, between 200 to 1920 MHz. The deliberated values are used to determine the typical field strength and numerous correction elements. The correction factors include adjusting to the degree of urbanization, terrain roughness, base station antenna height, mobile phone antenna height and localized obstruction. The Okumura model is especially suitable in urban area for standard coverage calculation where numerous obstructions and buildings exist.

The Cost 231 Model, also called the Hata style PCS extension, is used in most industrial RF planning tools for portable telephony. The coverage of the Cost 231 model is frequency between truck to 2000 MHz, transmitter useful antenna height between 30 in order to 200 m, receiver effective antenna height between 1 to 10 m and link distance right from 1 to 20 km. The Cost 231 model is restricted to application the place that the base station antenna is above adjacent roof tops.

The Egli model is a simplified model based on empirical match of measured data to mathematical formula. Its easy implementation makes it a popular choice for use in the very first analysis. It assumes gentle rolling hill height of approximately 50 foot and no terrain elevation data between transmitter and receiver is needed for any model. The median path damage is adjusted for the height involving transmit and receive antenna above ground. The model consists of a single equation for the propagation loss.

ITU terrain model is based on diffraction concept that provides a method to predict median course loss. The model predicts course loss as a function of the height of path blockage and the earliest Fresnel zone for the transmission hyperlink. The model is ideal for modeling line-of-sight link in any terrain and is good for any frequency and path length. The model accounts for obstructions down the middle of the communication link, hence it can be suitable to be used both inside locations and open fields. The type is considered valid for losses above 15 dB.