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MULTIPATH PROPAGATION
Presenting by:
BHUPENDRA SAHU0158EC1010177
thSEM, REC
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DEFINATION
A radio signal flow out in different directions asit radiates
away from the broadcast Antenna.
The transmission medium is the radio channel
b/w Tx and Rx for wireless communication. Signal can get from
the transmitter to the
receiver through a number of different
propagation paths.
Signal diffracted by different interacting objects
(Ios) in the environments.
i.e. house,windows,wall,mountains,trees.
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MULTIPATH PROPAGATION Reflectionit is the change in direction of
a wavefront
at an interface b/w two different medium.
Diffractionit pattern of red laser beam made on a plate
after passing a small circular hole in other plate, it referto
various phenomena which occurs when signal
encounters a surface.
Scatteringoccurs when incoming signal hits an object
,may also refer to particle-particle collision b/w
moleculer,atom,electron,photon etc.
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MULTIPATH PROPAGATION
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FADING
The communication between the base station and mobile
station in mobile systems is mostly non-LOS.
The LOS path between the transmitter and the receiver isaffected
by terrain and obstructed by buildings and other
objects.
The mobile station is also moving in different directions
at different speeds.
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TYPES OF FADING
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PROPAGATION MODESGround-wave propagation
Sky-wave propagation
Line-of-sight propagation
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GROUND WAVE PROPAGATION
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GROUND WAVE PROPAGATIONFollows contour of the earth
Can Propagate considerable distances
Frequencies up to 2 MHzExample
AM radio
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SKY WAVE PROPAGATION Signal reflected from ionized layer of
atmosphere
back down to earth
Signal can travel a number of hops, back and
forth between ionosphere and earths surface
Reflection effect caused by refraction
Examples
Amateur radio
CB radio
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LINE-OF-SIGHT PROPAGATION
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LINE-OF-SIGHT PROPAGATION Transmitting and receiving antennas
must be within line
of sight
Satellite communicationsignal above 30 MHz notreflected by
ionosphere
Ground communicationelectro-magnetic waves
travelling in a straight line
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LINE-OF-SIGHT EQUATIONS Optical line of sight
Effective, or radio, line of sight
d= distance between antenna and
horizon (km)h = antenna height (m)
K = adjustment factor to account for
refraction, rule of thumb K = 4/3
hd 57.3
hd 57.3
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LINE-OF-SIGHT EQUATIONSMaximum distance between two antennas
for
LOS propagation:
h1 = height of antenna one
h2 = height of antenna two
2157.3 hh
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