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The decibel originates from methods used to quantify signal loss in telegraph and telephone circuits. Until the mid-1920s, the unit for loss was miles of standard cable (MSC). 1 MSC corresponded to the loss of power over one mile (approximately 1.6 km) of standard telephone cable at a frequency of 5000 radians per second (795.8 Hz), and matched closely the smallest attenuation detectable to a ...
In engineering, attenuation is usually measured in units of decibels per unit length of medium (dB/cm, dB/km, etc.) and is represented by the attenuation coefficient of the medium in question. [1] Attenuation also occurs in earthquakes; when the seismic waves move farther away from the hypocenter, they grow smaller as they are attenuated by the ...
is the reference distance, usually 1 km (or 1 mile) for a large cell and 1 m to 10 m for a microcell. [1] is the path loss exponent. is a normal (Gaussian) random variable with zero mean, reflecting the attenuation (in decibels) caused by flat fading [citation needed]. In the case of no fading, this variable is 0.
In telecommunications, the free-space path loss (FSPL) (also known as free-space loss, FSL) is the attenuation of radio energy between the feedpoints of two antennas that results from the combination of the receiving antenna's capture area plus the obstacle-free, line-of-sight (LoS) path through free space (usually air). [1]
(dB) ≈ 36.6 dB + 20 log10[frequency (MHz)] + 20 log10[distance (miles)] These alternative forms can be derived by substituting wavelength with the ratio of propagation velocity ( c , approximately 3 × 10 8 m/s ) divided by frequency, and by inserting the proper conversion factors between km or miles and meters, and between MHz and (1/s).
Path loss normally includes propagation losses caused by the natural expansion of the radio wave front in free space (which usually takes the shape of an ever-increasing sphere), absorption losses (sometimes called penetration losses), when the signal passes through media not transparent to electromagnetic waves, diffraction losses when part of the radiowave front is obstructed by an opaque ...
Unit: decibel (dB). L 0 = The reference path loss along 1 km. Unit: decibel (dB). = The slope of the path loss curve. Unit: decibels per decade. d = The distance on which the path loss is to be calculated. Unit: kilometer (km). F A = Adjustment factor H ET = Effective height of terrain. Unit: meter (m).
Mathematically, transmission loss is measured in dB scale and in general it can be defined using the following formula: TL = | | dB. where: is the power of incident wave coming towards a defined area (or structure);