Radio wave propagation can be categorized as LOS (Line Of Sight) and non-LOS modes. LOS is immediate issue-to-place propagation with no obstructions in concerning. Non-LOS is oblique propagation in the absence of LOS route which consists of diffraction, reflection and scattering. In the HF band (3 – 30 MHz), propagation is principally utilizing sky wave for long length communications. VHF and UHF (30 MHz – 3 GHz) waves vacation by LOS and floor bounce propagation. The SHF (3 to 30 GHz) wave uses strictly LOS propagation.
The aim of propagation modeling is to establish the probability of satisfactory efficiency of a wi-fi process that relies upon on radio wave propagation. For RF systems scheduling, the modeling of propagation is for the objective of RF protection assessment. This investigation makes use of the propagation product and terrain details to predict the RF protection place of a transmitter, the gained sign toughness at the stop of a wi-fi backlink, the route reduction from the transmitter to a length receiver, the antenna tilt angle of the transmitter, the minimum antenna height to establish Line of Sight communication path and channel impairment this sort of as delay distribute because of to multi-route fading.
Propagation types for diverse applications, environments and terrains had been created by the US authorities, non-public organizations and typical body these types of as Intercontinental Telecommunications Union (ITU). These models are based on big sum of empirical details gathered for the function of characterizing propagation for that application. Since propagation versions are developed utilizing statistical techniques, no single product will particularly in good shape any specific application. It is a excellent concept to utilize two or much more unbiased styles and use the effects as bounds on the expected efficiency. The adhering to are a record of most normally utilized in the vicinity of-earth propagation styles.
Longley-Rice
The Longley-Rice design predicts extensive phrase median transmission reduction in excess of irregular terrain. It is made for frequency from 20 MHz to 20 GHz and path size from 1 to 2000 Km. The product accounts for terrain, weather, subsoil problems and floor curvature. Longley-Rice model has two modes, stage-to-point and region. The level-to-point manner works by using element terrain details and traits to predict path reduction, while the area manner takes advantage of standard data about the terrain properties to predict path decline.
Okumura
The Okumura product is primarily based on the measurements designed in Tokyo in 1960, amongst 200 to 1920 MHz. The measured values are made use of to figure out the median industry energy and several correction variables. The correction aspects incorporate adjustment to the degree of urbanization, terrain roughness, base station antenna top, mobile antenna peak and localized obstruction. The Okumura model is specifically applicable in urban region for common coverage calculation the place numerous obstructions and buildings exist.
Value 231
The Price 231 Model, also called the Hata design PCS extension, is applied in most commercial RF scheduling applications for cell telephony. The protection of the Price 231 product is frequency in between 1500 to 2000 MHz, transmitter productive antenna top concerning 30 to 200 m, receiver successful antenna peak involving 1 to 10 m and url distance from 1 to 20 km. The Price tag 231 product is limited to software the place the foundation station antenna is over adjacent roof tops.
Egli
The Egli model is a simplified model centered on empirical match of measured information to mathematical formula. Its simplicity of implementation makes it a popular alternative for use in the first examination. It assumes light rolling hill peak of close to 50 feet and no terrain elevation info among the transmitter and receiver is desired for the design. The median route reduction is adjusted for the top of transmit and acquire antenna higher than ground. The product is composed of a single equation for the propagation reduction.
ITU
ITU terrain model is centered on diffraction idea that offers a method to predict median route decline. The product predicts route loss as a functionality of the top of route blockage and the initial Fresnel zone for the transmission connection. The model is excellent for modeling line-of-sight link in any terrain and is good for any frequency and path size. The design accounts for obstructions in the center of the conversation url, therefore it is suitable to be applied the two within towns and open fields. The model is regarded as legitimate for losses above 15 dB.
