Main article: Log-distance path loss model Small-scale fading refers to the rapid changes in radio signal amplitude in a short period of time or distance of travel. The total power of interfering waves in a Rayleigh fading scenario varies quickly as a function of space (which is known as small scale fading). Multipath waves combine at the receiver antenna, resulting in a received signal that may vary widely, depending on the distribution of the intensity and relative propagation time of the waves and bandwidth of the transmitted signal. The signal radiated by a transmitter may also travel along many and different paths to a receiver simultaneously this effect is called multipath. 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 obstacle, and losses caused by other phenomena. ( August 2017) ( Learn how and when to remove this template message) Unsourced material may be challenged and removed. Please help improve this section by adding citations to reliable sources. Path loss is also influenced by terrain contours, environment (urban or rural, vegetation and foliage), propagation medium (dry or moist air), the distance between the transmitter and the receiver, and the height and location of antennas. Path loss may be due to many effects, such as free-space loss, refraction, diffraction, reflection, aperture- medium coupling loss, and absorption. This term is commonly used in wireless communications and signal propagation. Path loss is a major component in the analysis and design of the link budget of a telecommunication system. Path loss, or path attenuation, is the reduction in power density ( attenuation) of an electromagnetic wave as it propagates through space. JSTOR ( August 2017) ( Learn how and when to remove this template message).Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.
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