mobile radio propagation
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Mobile Radio PropagationMobile Radio PropagationMobile Radio PropagationMobile Radio Propagation Mobile radio channel is an important factor in Mobile radio channel is an important factor in
wireless systems.wireless systems.
Wired channels are stationary and Wired channels are stationary and predictable, while radio channels are random predictable, while radio channels are random and have complex models.and have complex models.
Modeling of radio channels is done in Modeling of radio channels is done in statistical fashion based on receiver statistical fashion based on receiver measurements.measurements.
Mobile radio channel is an important factor in Mobile radio channel is an important factor in wireless systems.wireless systems.
Wired channels are stationary and Wired channels are stationary and predictable, while radio channels are random predictable, while radio channels are random and have complex models.and have complex models.
Modeling of radio channels is done in Modeling of radio channels is done in statistical fashion based on receiver statistical fashion based on receiver measurements.measurements.
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Types of propagation modelsTypes of propagation modelsTypes of propagation modelsTypes of propagation models Large scale propagation models Large scale propagation models
To predict the average signal strength at a To predict the average signal strength at a given distance from the transmittergiven distance from the transmitter
Controlled by signal decay with distance Controlled by signal decay with distance
Small scale or fading models.Small scale or fading models. To predict the signal strength at close To predict the signal strength at close
distance to a particular location distance to a particular location Controlled by multipath and Doppler Controlled by multipath and Doppler
effects.effects.
Large scale propagation models Large scale propagation models To predict the average signal strength at a To predict the average signal strength at a
given distance from the transmittergiven distance from the transmitter Controlled by signal decay with distance Controlled by signal decay with distance
Small scale or fading models.Small scale or fading models. To predict the signal strength at close To predict the signal strength at close
distance to a particular location distance to a particular location Controlled by multipath and Doppler Controlled by multipath and Doppler
effects.effects.
33
Radio signal patternRadio signal patternRadio signal patternRadio signal pattern-30-30-30-30
-40-40-40-40
-50-50-50-50
-60-60-60-60
-70-70-70-7016161616 18181818 20202020 22222222 24242424 26262626 2828282814141414
T-R Separation (meters)T-R Separation (meters)T-R Separation (meters)T-R Separation (meters)
Rec
eive
d Po
wer
(dB
m)
Rec
eive
d Po
wer
(dB
m)
Rec
eive
d Po
wer
(dB
m)
Rec
eive
d Po
wer
(dB
m)
44
Measured signal parametersMeasured signal parametersMeasured signal parametersMeasured signal parameters
Electrical Field (Volts/m)Electrical Field (Volts/m)Magnitude E = IMagnitude E = IEEI I
Vector Vector Direction Direction EE = = xxEExx + + yyEEyy + + zzEEzz
Electrical Field (Volts/m)Electrical Field (Volts/m)Magnitude E = IMagnitude E = IEEI I
Vector Vector Direction Direction EE = = xxEExx + + yyEEyy + + zzEEzz
Power (Watts or dBm)Power (Watts or dBm)
Power is scalar quantity and easier to Power is scalar quantity and easier to measure.measure.
Power (Watts or dBm)Power (Watts or dBm)
Power is scalar quantity and easier to Power is scalar quantity and easier to measure.measure.
55
Relation between Watts and dBm Relation between Watts and dBm Relation between Watts and dBm Relation between Watts and dBm
P (dBm) = 10 logP (dBm) = 10 log1010 [ [ PP (mW)](mW)]
P (dBm) = 10 logP (dBm) = 10 log1010 [ [ PP (mW)](mW)]
P(mW) P(dBm)
10 10
1 0
10-1 -10
10-2 -20
10-6 -60
66
Physical propagation modelsPhysical propagation modelsPhysical propagation modelsPhysical propagation models Free Space PropagationFree Space Propagation
Transmitter/receiver have clear LOS pathTransmitter/receiver have clear LOS path ReflectionReflection
Wave reaches receiver after reflection off Wave reaches receiver after reflection off surfaces larger than wavelengthsurfaces larger than wavelength
DiffractionDiffraction Wave reaches receiver by bending at sharp Wave reaches receiver by bending at sharp
edges (peaks) or curved surfaces (earth).edges (peaks) or curved surfaces (earth). ScatteringScattering
Wave reaches receiver after bouncing off Wave reaches receiver after bouncing off objects smaller than wavelength (snow, rain).objects smaller than wavelength (snow, rain).
Free Space PropagationFree Space Propagation Transmitter/receiver have clear LOS pathTransmitter/receiver have clear LOS path
ReflectionReflection Wave reaches receiver after reflection off Wave reaches receiver after reflection off
surfaces larger than wavelengthsurfaces larger than wavelength DiffractionDiffraction
Wave reaches receiver by bending at sharp Wave reaches receiver by bending at sharp edges (peaks) or curved surfaces (earth).edges (peaks) or curved surfaces (earth).
ScatteringScattering Wave reaches receiver after bouncing off Wave reaches receiver after bouncing off
objects smaller than wavelength (snow, rain).objects smaller than wavelength (snow, rain).
77
Free Space PropagationFree Space PropagationFree Space PropagationFree Space Propagation Transmitter and receiver have clear, Transmitter and receiver have clear,
unobstructed LOS path between them.unobstructed LOS path between them.
(Courtesy: webbroadband.blogspot.com)(Courtesy: webbroadband.blogspot.com)
Transmitter and receiver have clear, Transmitter and receiver have clear, unobstructed LOS path between them.unobstructed LOS path between them.
(Courtesy: webbroadband.blogspot.com)(Courtesy: webbroadband.blogspot.com)
88
Friis transmission equationFriis transmission equationFriis transmission equationFriis transmission equation
PPrr = P = Ptt G Gtt G Grr 22
(4(4))22 d d22 L L
PPtt = Transmitted Power (W)= Transmitted Power (W)PPrr = Received Power (W) = Received Power (W)GGtt = Transmitter antenna gain = Transmitter antenna gain GGrr = Receiver antenna gain = Receiver antenna gain LL = System loss factor = System loss factor Due to line losses, but not due to propagationDue to line losses, but not due to propagationL L 1 1
PPrr = P = Ptt G Gtt G Grr 22
(4(4))22 d d22 L L
PPtt = Transmitted Power (W)= Transmitted Power (W)PPrr = Received Power (W) = Received Power (W)GGtt = Transmitter antenna gain = Transmitter antenna gain GGrr = Receiver antenna gain = Receiver antenna gain LL = System loss factor = System loss factor Due to line losses, but not due to propagationDue to line losses, but not due to propagationL L 1 1
99
Antenna GainAntenna GainAntenna GainAntenna Gain Power Gain of antenna Power Gain of antenna
GG = 4 = 4AAee / / 22, ,
AAee is effective aperture area of antenna is effective aperture area of antenna
Wavelength Wavelength = c / f (Hz) = c / f (Hz) = 3 • 10= 3 • 1088 / f , meters / f , meters
Power Gain of antenna Power Gain of antenna
GG = 4 = 4AAee / / 22, ,
AAee is effective aperture area of antenna is effective aperture area of antenna
Wavelength Wavelength = c / f (Hz) = c / f (Hz) = 3 • 10= 3 • 1088 / f , meters / f , meters
1010
Relation between Electric field and PowerRelation between Electric field and PowerRelation between Electric field and PowerRelation between Electric field and Power
Received powerReceived power
PPrr = I = IEErrII2 2 22 G Grr
44 Impedance of medium: Impedance of medium: = = / /
For air or vacuum: For air or vacuum: = (4= (4 • 10 • 10-7-7) /(8.85 • 10) /(8.85 • 10-12-12 ) ) = 377 = 377
Received powerReceived power
PPrr = I = IEErrII2 2 22 G Grr
44 Impedance of medium: Impedance of medium: = = / /
For air or vacuum: For air or vacuum: = (4= (4 • 10 • 10-7-7) /(8.85 • 10) /(8.85 • 10-12-12 ) ) = 377 = 377
1111
ExampleExampleExampleExample
If the received power is PIf the received power is Prr = 7 • 10 = 7 • 10 -10-10 W, W, antenna gain Gantenna gain Grr = 2 and transmitting frequency = 2 and transmitting frequency is 900 MHz, determine the electric field strength is 900 MHz, determine the electric field strength at the receiver. at the receiver.
If the received power is PIf the received power is Prr = 7 • 10 = 7 • 10 -10-10 W, W, antenna gain Gantenna gain Grr = 2 and transmitting frequency = 2 and transmitting frequency is 900 MHz, determine the electric field strength is 900 MHz, determine the electric field strength at the receiver. at the receiver.
1212
SolutionSolutionSolutionSolution
f = 900 MHz =f = 900 MHz = > >
= (3 • 10= (3 • 1088) / (900 • 10) / (900 • 1066) = 0.33 m) = 0.33 m
From field-power equation:From field-power equation:IIEErrII = [(P= [(Prr • • • 4 • 4) / () / ( 22 • G • Grr)])]1/21/2
= [(7 • 10= [(7 • 10 -10-10 • 377 • 4 • 377 • 4) / (0.33) / (0.3322 • 2)] • 2)]1/21/2
= 0.0039 V/m= 0.0039 V/m
f = 900 MHz =f = 900 MHz = > >
= (3 • 10= (3 • 1088) / (900 • 10) / (900 • 1066) = 0.33 m) = 0.33 m
From field-power equation:From field-power equation:IIEErrII = [(P= [(Prr • • • 4 • 4) / () / ( 22 • G • Grr)])]1/21/2
= [(7 • 10= [(7 • 10 -10-10 • 377 • 4 • 377 • 4) / (0.33) / (0.3322 • 2)] • 2)]1/21/2
= 0.0039 V/m= 0.0039 V/m
1313
ExampleExampleExampleExampleA transmitter produces 50W of power. A transmitter produces 50W of power. If this power is applied to a unity gain antenna If this power is applied to a unity gain antenna with 900 MHz carrier frequency, find the received with 900 MHz carrier frequency, find the received power at a LOS distance of 100 m from the power at a LOS distance of 100 m from the antenna. What is the received power at 10 km? antenna. What is the received power at 10 km? Assume unity gain for the receiver antenna.Assume unity gain for the receiver antenna.
A transmitter produces 50W of power. A transmitter produces 50W of power. If this power is applied to a unity gain antenna If this power is applied to a unity gain antenna with 900 MHz carrier frequency, find the received with 900 MHz carrier frequency, find the received power at a LOS distance of 100 m from the power at a LOS distance of 100 m from the antenna. What is the received power at 10 km? antenna. What is the received power at 10 km? Assume unity gain for the receiver antenna.Assume unity gain for the receiver antenna.
1414
SolutionSolutionSolutionSolution
PPrr = = PPtt G Gtt G Grr 22
(4(4))22 d d22 L L
PPtt = 50 W, G = 50 W, Gtt = 1, G = 1, Grr = 1, L = 1, d = 100 m = 1, L = 1, d = 100 m = (3 • 10= (3 • 1088) / (900 • 10) / (900 • 1066) = 0.33 m) = 0.33 m
PPrr = = PPtt G Gtt G Grr 22
(4(4))22 d d22 L L
PPtt = 50 W, G = 50 W, Gtt = 1, G = 1, Grr = 1, L = 1, d = 100 m = 1, L = 1, d = 100 m = (3 • 10= (3 • 1088) / (900 • 10) / (900 • 1066) = 0.33 m) = 0.33 m
Solving, Pr = 3.5 • 10-6 W
Pr (10 km) = Pr (100 m) • (100/10000)2
= 3.5 • 10-6 • (1/100)2 = 3.5 • 10-10 W
1515
Electric Properties of Material BodiesElectric Properties of Material BodiesElectric Properties of Material BodiesElectric Properties of Material Bodies Fundamental constantsFundamental constants
Permittivity Permittivity = = 00 rr , , Farads/mFarads/m
Permeability Permeability = = 00 rr , ,Henries/mHenries/m
Conductivity Conductivity , Siemens/m, Siemens/m Types of materialsTypes of materials
Dielectrics – allow EM waves to passDielectrics – allow EM waves to pass Conductors – block EM wavesConductors – block EM waves Metamaterials – bend EM wavesMetamaterials – bend EM waves
Fundamental constantsFundamental constants
Permittivity Permittivity = = 00 rr , , Farads/mFarads/m
Permeability Permeability = = 00 rr , ,Henries/mHenries/m
Conductivity Conductivity , Siemens/m, Siemens/m Types of materialsTypes of materials
Dielectrics – allow EM waves to passDielectrics – allow EM waves to pass Conductors – block EM wavesConductors – block EM waves Metamaterials – bend EM wavesMetamaterials – bend EM waves
1616
Reflection at dielectric boundariesReflection at dielectric boundariesReflection at dielectric boundariesReflection at dielectric boundaries
EErr = = : Reflection coefficient : Reflection coefficient
EEtt = T = 1 + = T = 1 + : Transmission coefficient : Transmission coefficient
EErr = = : Reflection coefficient : Reflection coefficient
EEtt = T = 1 + = T = 1 + : Transmission coefficient : Transmission coefficientEEiiEEii
EEiiEEiiEEiiEEii EErrEErr
EEttEEtt
iiii rrrr
ii = = rrii = = rr
1717
Vertical Polarization Vertical Polarization Vertical Polarization Vertical Polarization
EEttEEtt
EEiiEEii EErrEErr
iiii rrrr
HHiiHHii HHrrHHrr11, , 11, , 1111, , 11, , 11
22, , 22, , 2222, , 22, , 22 tt tt
||||= = 22 sinsintt - - 11 sinsinii
22 sin sintt + + 11 sinsinii
||||= = 22 sinsintt - - 11 sinsinii
22 sin sintt + + 11 sinsinii
1818
Horizontal PolarizationHorizontal PolarizationHorizontal PolarizationHorizontal Polarization
EEiiEEii EErrEErr
EEttEEtt
iiii rrrr
HHiiHHii HHrrHHrr11, , 11, , 1111, , 11, , 11
22, , 22, , 2222, , 22, , 22 tt tt
T T = = 22 sinsintt - - 11 sinsinii
22 sin sintt + + 11 sinsinii
T T = = 22 sinsintt - - 11 sinsinii
22 sin sintt + + 11 sinsinii
1919
Reflection from Perfect Conductor (Reflection from Perfect Conductor (EETT =0) =0)Reflection from Perfect Conductor (Reflection from Perfect Conductor (EETT =0) =0)
Vert. polarizationVert. polarization Horiz. polarizationHoriz. polarization
ii == rr ii == rr
EEii = = EErr EEii = = - E- Err
Vert. polarizationVert. polarization Horiz. polarizationHoriz. polarization
ii == rr ii == rr
EEii = = EErr EEii = = - E- Err
EEiiEEii EErrEErr
EEttEEtt
iiii rrrr
2020
Ground Reflection (2-Ray Model)Ground Reflection (2-Ray Model)Ground Reflection (2-Ray Model)Ground Reflection (2-Ray Model)
EEiiEEii
iiii 0000
EELOSLOSEELOSLOS
EErr=E=EggEErr=E=Egg
EETOTTOT = E = ELOS LOS +E+EggEETOTTOT = E = ELOS LOS +E+Egg
R R (receiver)(receiver)R R (receiver)(receiver)
hhrrhhrr
hhtthhtt
T T (transmitter)(transmitter)T T (transmitter)(transmitter)
dddd
2121
Field EquationsField EquationsField EquationsField Equations
d = several kmsd = several kms
hhtt = 50-100m = 50-100m
EETOTTOT= E= ELOS LOS + E+ Egg
EETOTTOT(d) = (d) =
For d > 20hFor d > 20htthhrr / /
Received power PReceived power Prr==
d = several kmsd = several kms
hhtt = 50-100m = 50-100m
EETOTTOT= E= ELOS LOS + E+ Egg
EETOTTOT(d) = (d) =
For d > 20hFor d > 20htthhrr / /
Received power PReceived power Prr==
2004
d
hhdE rt
4
22
d
hhGGP rtrtt
2222
ExampleExampleExampleExampleA mobile is located 5 km away from a A mobile is located 5 km away from a base station, and uses a vertical base station, and uses a vertical /4 /4 monopole antenna with a gain of monopole antenna with a gain of 2.55dB to receive cellular radio signals. 2.55dB to receive cellular radio signals. The electric field at 1 km from the The electric field at 1 km from the transmitter is measured to be 10transmitter is measured to be 10 -3-3 V/m. V/m. The carrier frequency used is 900 MHz.The carrier frequency used is 900 MHz.(a) Find the length and gain of the (a) Find the length and gain of the receiving antenna.receiving antenna.
A mobile is located 5 km away from a A mobile is located 5 km away from a base station, and uses a vertical base station, and uses a vertical /4 /4 monopole antenna with a gain of monopole antenna with a gain of 2.55dB to receive cellular radio signals. 2.55dB to receive cellular radio signals. The electric field at 1 km from the The electric field at 1 km from the transmitter is measured to be 10transmitter is measured to be 10 -3-3 V/m. V/m. The carrier frequency used is 900 MHz.The carrier frequency used is 900 MHz.(a) Find the length and gain of the (a) Find the length and gain of the receiving antenna.receiving antenna.
2323
ExampleExampleExampleExampleA mobile is located 5 km away from a A mobile is located 5 km away from a base station, and uses a vertical base station, and uses a vertical /4 /4 monopole antenna with a gain of 2.55dB monopole antenna with a gain of 2.55dB to receive cellular radio signals. to receive cellular radio signals. The electric field at 1 km from the transmitter The electric field at 1 km from the transmitter is measured to be 10is measured to be 10-3-3 V/m. V/m. The carrier frequency used is 900 MHz.The carrier frequency used is 900 MHz.
(b) Find the received power at the mobile (b) Find the received power at the mobile using the 2-way ground model assuming the using the 2-way ground model assuming the height of the transmitting antenna is 50 m and height of the transmitting antenna is 50 m and receiving antenna is 1.5 m above the ground.receiving antenna is 1.5 m above the ground.
A mobile is located 5 km away from a A mobile is located 5 km away from a base station, and uses a vertical base station, and uses a vertical /4 /4 monopole antenna with a gain of 2.55dB monopole antenna with a gain of 2.55dB to receive cellular radio signals. to receive cellular radio signals. The electric field at 1 km from the transmitter The electric field at 1 km from the transmitter is measured to be 10is measured to be 10-3-3 V/m. V/m. The carrier frequency used is 900 MHz.The carrier frequency used is 900 MHz.
(b) Find the received power at the mobile (b) Find the received power at the mobile using the 2-way ground model assuming the using the 2-way ground model assuming the height of the transmitting antenna is 50 m and height of the transmitting antenna is 50 m and receiving antenna is 1.5 m above the ground.receiving antenna is 1.5 m above the ground.
2424
Solution:Solution:
d0 = 1 km
E0 = 10 -3 V/m
d0 = 1 km
E0 = 10 -3 V/m
ht = 50 mht = 50 m hr = 1.5 mhr = 1.5 m
d = 5 kmd = 5 km
2525
(a) (a)
f = 900 MHzf = 900 MHz
= (3 • 10= (3 • 108) / (900 • 10) / (900 • 106) = 0.33 m) = 0.33 m
Length of receiving antenna,Length of receiving antenna,
L = L = / 4 = 0.33/4 = 0.0833 m = 8.33 cm / 4 = 0.33/4 = 0.0833 m = 8.33 cm
(a) (a)
f = 900 MHzf = 900 MHz
= (3 • 10= (3 • 108) / (900 • 10) / (900 • 106) = 0.33 m) = 0.33 m
Length of receiving antenna,Length of receiving antenna,
L = L = / 4 = 0.33/4 = 0.0833 m = 8.33 cm / 4 = 0.33/4 = 0.0833 m = 8.33 cm
2626
(b)
Gain of antenna = 2.55 dB = > 1.8
Er (d) =
= 2 • 10-3 • 1 • 103 • 2 • 50 • 1.5(5 • 103)2 • 0.333
= 113.1 • 10-6 V/m
(b)
Gain of antenna = 2.55 dB = > 1.8
Er (d) =
= 2 • 10-3 • 1 • 103 • 2 • 50 • 1.5(5 • 103)2 • 0.333
= 113.1 • 10-6 V/m
2004
d
hhdE rt
2727
Pr (d)
= I Er I2 2 Gr
4= (113.1 • 10-6) 2 • (0.333) 2 • 1.8
377 4= 5.4 • 10-13 W
= -92.68 dBm
Pr (d)
= I Er I2 2 Gr
4= (113.1 • 10-6) 2 • (0.333) 2 • 1.8
377 4= 5.4 • 10-13 W
= -92.68 dBm
2828
DiffractionDiffractionDiffractionDiffraction Diffraction allows radio signals Diffraction allows radio signals
to propagate around the curved to propagate around the curved surface or propagate behind surface or propagate behind obstructions.obstructions.
Based on Huygen’s principle of Based on Huygen’s principle of wave propagation.wave propagation.
Diffraction allows radio signals Diffraction allows radio signals to propagate around the curved to propagate around the curved surface or propagate behind surface or propagate behind obstructions.obstructions.
Based on Huygen’s principle of Based on Huygen’s principle of wave propagation.wave propagation.
2929
Knife-edge Diffraction GeometryKnife-edge Diffraction GeometryKnife-edge Diffraction GeometryKnife-edge Diffraction Geometry(a) T is transmitter and R is receiver, (a) T is transmitter and R is receiver, with an infinite knife-edge obstruction with an infinite knife-edge obstruction blocking the line-of-sight path.blocking the line-of-sight path.
(a) T is transmitter and R is receiver, (a) T is transmitter and R is receiver, with an infinite knife-edge obstruction with an infinite knife-edge obstruction blocking the line-of-sight path.blocking the line-of-sight path.
hhrrhhrrhhobsobshhobsobshhtthhtt
RRRRTTTT hhhh
dd11dd11 dd22dd22
3030
Knife-edge Diffraction GeometryKnife-edge Diffraction GeometryKnife-edge Diffraction GeometryKnife-edge Diffraction Geometry(b) T & R are not the same height...(b) T & R are not the same height...(b) T & R are not the same height...(b) T & R are not the same height...
hhrrhhrr
h’h’h’h’
hhtthhtt
RRRRTTTT hhhh
dd11dd11 dd22dd22
3131
Knife-edge Diffraction GeometryKnife-edge Diffraction GeometryKnife-edge Diffraction GeometryKnife-edge Diffraction Geometry
...If ...If and and are small and are small and h<<dh<<d11 and and dd22, , then then h h & & h’h’ are virtually identical and are virtually identical and the geometry may be redrawn as in (c).the geometry may be redrawn as in (c).
...If ...If and and are small and are small and h<<dh<<d11 and and dd22, , then then h h & & h’h’ are virtually identical and are virtually identical and the geometry may be redrawn as in (c).the geometry may be redrawn as in (c).
hhrrhhrr
h’h’h’h’
hhtthhtt
RRRRTTTT hhhh
dd11dd11 dd22dd22
3232
Knife-edge Diffraction GeometryKnife-edge Diffraction GeometryKnife-edge Diffraction GeometryKnife-edge Diffraction Geometry(c) Equivalent where the smallest height (c) Equivalent where the smallest height (in this case (in this case hhr r )) is subtracted from all is subtracted from all other heights.other heights.
(c) Equivalent where the smallest height (c) Equivalent where the smallest height (in this case (in this case hhr r )) is subtracted from all is subtracted from all other heights.other heights.
hhtt -- hhrrhhtt -- hhrrRRRR
TTTT
dd11dd11 dd22dd22
hhobsobs-h-hrrhhobsobs-h-hrr
3333
AssumptionsAssumptionsAssumptionsAssumptions
h << d1, d2
h >>
Excess path length
h << d1, d2
h >>
Excess path length
21
212
2
)(
dd
ddh
21
21
2
)(
dd
ddh
3434
...Assumptions...Assumptions...Assumptions...Assumptions
h << dh << d11, d, d22
h >> h >>
Phase differencePhase difference == 2 2 / / == 2 2 h h2 2 (d(d11 + d + d22 ) )
2 2 d d1 1 dd2 2
h << dh << d11, d, d22
h >> h >>
Phase differencePhase difference == 2 2 / / == 2 2 h h2 2 (d(d11 + d + d22 ) )
2 2 d d1 1 dd2 2
3535
Diffraction ParameterDiffraction ParameterDiffraction ParameterDiffraction Parameter
v =
=
v =
=
2
21
21 )(2
dd
ddh
3636
Three CasesThree CasesThree CasesThree Cases Case I: h > 0Case I: h > 0 Case II: h = 0Case II: h = 0 Case III: h < 0Case III: h < 0
Case I: h > 0Case I: h > 0 Case II: h = 0Case II: h = 0 Case III: h < 0Case III: h < 0
3737
Case I: h > 0Case I: h > 0Case I: h > 0Case I: h > 0 and and are positive since are positive since hh is positive. is positive. and and are positive since are positive since hh is positive. is positive.
hhhhRRRR
TTTT
dd11dd11 dd22dd22
3838
Case II: h = 0Case II: h = 0Case II: h = 0Case II: h = 0 and and equal 0, since equal 0, since hh equals 0. equals 0. and and equal 0, since equal 0, since hh equals 0. equals 0.
RRRRTTTTdd11dd11 dd22dd22
3939
Case III: h < 0Case III: h < 0Case III: h < 0Case III: h < 0 and and are negative, since are negative, since hh is negative. is negative. and and are negative, since are negative, since hh is negative. is negative.
hhhhRRRR
TTTTdd11dd11 dd22dd22
4040
The electric field strength of The electric field strength of the diffracted wave is given by:the diffracted wave is given by:
Ed = F(v) • Eo
where Eo is the free space field strength in the absence of both ground and knife edge.
The electric field strength of The electric field strength of the diffracted wave is given by:the diffracted wave is given by:
Ed = F(v) • Eo
where Eo is the free space field strength in the absence of both ground and knife edge.
4141
Approximate Value of Approximate Value of Fresnel Integral F(v):Fresnel Integral F(v):Approximate Value of Approximate Value of Fresnel Integral F(v):Fresnel Integral F(v):
GGdd (dB) = 20(dB) = 20 log Ilog I F(v)F(v) IIGGdd (dB) = 20(dB) = 20 log Ilog I F(v)F(v) II
4242
v Rangev Range GGdd (dB) (dB)
vv -1 -1 00
-1-1vv 0 0 20 log (0.5 – 0.62 v)20 log (0.5 – 0.62 v)
00vv11 20 log (0.5 e20 log (0.5 e-0.95v-0.95v ))
11 vv 2.4 2.4 20 log (0.4 –20 log (0.4 –
vv2.42.4 20 log (0.225 /20 log (0.225 / v)v)
v Rangev Range GGdd (dB) (dB)
vv -1 -1 00
-1-1vv 0 0 20 log (0.5 – 0.62 v)20 log (0.5 – 0.62 v)
00vv11 20 log (0.5 e20 log (0.5 e-0.95v-0.95v ))
11 vv 2.4 2.4 20 log (0.4 –20 log (0.4 –
vv2.42.4 20 log (0.225 /20 log (0.225 / v)v)
))1.038.0(1184.0 2v
4343
Example Example Example Example Compute the diffraction loss Compute the diffraction loss between the transmitter and between the transmitter and receiver assuming: receiver assuming:
= 1/3= 1/3 m m
dd11 = 1 = 1 km km
dd2 2 = 1= 1 km km
h = 25h = 25 mm
Compute the diffraction loss Compute the diffraction loss between the transmitter and between the transmitter and receiver assuming: receiver assuming:
= 1/3= 1/3 m m
dd11 = 1 = 1 km km
dd2 2 = 1= 1 km km
h = 25h = 25 mm
4444
Solution:Solution:Solution:Solution:Given = 1/3 m
d1 = 1 kmd2 = 1 kmh = 25 m
V =
=
= 2.74
Given = 1/3 m d1 = 1 kmd2 = 1 kmh = 25 m
V =
=
= 2.74
21
21 )(2
dd
ddh
)1000)(1000)(3.0(
)10001000(225
4545
Using the table,
GGdd (dB) (dB) = 20 log (0.225/2.74)= -22 dBLoss = 22 dB
Using the table,
GGdd (dB) (dB) = 20 log (0.225/2.74)= -22 dBLoss = 22 dB
4646
ScatteringScatteringScatteringScattering When a radio wave impinges When a radio wave impinges
on a rough surface, the on a rough surface, the reflected energy is spread out reflected energy is spread out or diffused in all directions. or diffused in all directions. Ex., lampposts and foliage.Ex., lampposts and foliage.
The scattered field increases The scattered field increases the strength of the signal at the strength of the signal at the receiver.the receiver.
When a radio wave impinges When a radio wave impinges on a rough surface, the on a rough surface, the reflected energy is spread out reflected energy is spread out or diffused in all directions. or diffused in all directions. Ex., lampposts and foliage.Ex., lampposts and foliage.
The scattered field increases The scattered field increases the strength of the signal at the strength of the signal at the receiver.the receiver.
4747
Radar Cross Section (RCS) ModelRadar Cross Section (RCS) ModelRadar Cross Section (RCS) ModelRadar Cross Section (RCS) Model
RCS (Radar Cross Section) =RCS (Radar Cross Section) =
Power density of scattered wave Power density of scattered wave in direction of receiverin direction of receiver
Power density of radio wave incident Power density of radio wave incident on the scattering objecton the scattering object
RCS (Radar Cross Section) =RCS (Radar Cross Section) =
Power density of scattered wave Power density of scattered wave in direction of receiverin direction of receiver
Power density of radio wave incident Power density of radio wave incident on the scattering objecton the scattering object
4848
Radar Cross Section (RCS) ModelRadar Cross Section (RCS) ModelRadar Cross Section (RCS) ModelRadar Cross Section (RCS) Model
PPRR = P = PTT • G • GTT • • 22 • RCS • RCS
(4(4))3 3 • d• dTT 2 2 • d • dRR
2 2
Where,Where,
PPTT = Transmitted Power= Transmitted Power
GGTT = Gain of Transmitting antenna= Gain of Transmitting antenna
ddTT = Distance of scattering object = Distance of scattering object from Transmitterfrom Transmitter
ddRR = Distance of scattering object = Distance of scattering object from Receiverfrom Receiver
PPRR = P = PTT • G • GTT • • 22 • RCS • RCS
(4(4))3 3 • d• dTT 2 2 • d • dRR
2 2
Where,Where,
PPTT = Transmitted Power= Transmitted Power
GGTT = Gain of Transmitting antenna= Gain of Transmitting antenna
ddTT = Distance of scattering object = Distance of scattering object from Transmitterfrom Transmitter
ddRR = Distance of scattering object = Distance of scattering object from Receiverfrom Receiver
4949
Practical Link BudgetPractical Link BudgetPractical Link BudgetPractical Link Budget Most radio propagation models Most radio propagation models
are derived using a combination are derived using a combination of analytical and empirical of analytical and empirical models.models.
Empirical approach is based on Empirical approach is based on fitting curves or analytical fitting curves or analytical expressions that recreate a set expressions that recreate a set of measured data.of measured data.
Most radio propagation models Most radio propagation models are derived using a combination are derived using a combination of analytical and empirical of analytical and empirical models.models.
Empirical approach is based on Empirical approach is based on fitting curves or analytical fitting curves or analytical expressions that recreate a set expressions that recreate a set of measured data.of measured data.
5050
...Practical Link Budget...Practical Link Budget...Practical Link Budget...Practical Link Budget Advantages of empirical models;Advantages of empirical models;
Takes into account all propagation Takes into account all propagation factors, both known and unknown.factors, both known and unknown.
Disadvantages:Disadvantages:New models need to be measured for New models need to be measured for different environment or frequency.different environment or frequency.
Advantages of empirical models;Advantages of empirical models;
Takes into account all propagation Takes into account all propagation factors, both known and unknown.factors, both known and unknown.
Disadvantages:Disadvantages:New models need to be measured for New models need to be measured for different environment or frequency.different environment or frequency.
5151
T d0 R
PPTT PPRR(d(d00) ) PPRR(d)(d)
T d0 R
PPTT PPRR(d(d00) ) PPRR(d)(d)
Log-Distance Path ModelLog-Distance Path ModelLog-Distance Path ModelLog-Distance Path Model Over many years, some classical Over many years, some classical
propagation models have been propagation models have been developed, which are used to predict developed, which are used to predict large-scale coverage for mobile large-scale coverage for mobile communication system design.communication system design.
Over many years, some classical Over many years, some classical propagation models have been propagation models have been developed, which are used to predict developed, which are used to predict large-scale coverage for mobile large-scale coverage for mobile communication system design.communication system design.
5252
...Log-Distance Path Model...Log-Distance Path Model...Log-Distance Path Model...Log-Distance Path Model
Path loss at dPath loss at d00 = P = PTT/P(d/P(d00) = K(d) = K(d00))nn = PL(d = PL(d00))
Path loss at d = PPath loss at d = PTT/P(d) = K(d)/P(d) = K(d)nn = PL(d) = PL(d)
PL(d) / PL(dPL(d) / PL(d00) = (d/d) = (d/d00))n n
PL(d) [dB] = PL(dPL(d) [dB] = PL(d00) [dB] + 10n log) [dB] + 10n log1010 (d/d (d/d00))
Path loss at dPath loss at d00 = P = PTT/P(d/P(d00) = K(d) = K(d00))nn = PL(d = PL(d00))
Path loss at d = PPath loss at d = PTT/P(d) = K(d)/P(d) = K(d)nn = PL(d) = PL(d)
PL(d) / PL(dPL(d) / PL(d00) = (d/d) = (d/d00))n n
PL(d) [dB] = PL(dPL(d) [dB] = PL(d00) [dB] + 10n log) [dB] + 10n log1010 (d/d (d/d00))
5353
Received Power in Log-distance modelReceived Power in Log-distance modelReceived Power in Log-distance modelReceived Power in Log-distance model
PPRR(d) [dbm] = P(d) [dbm] = Ptt [dbm] – PL(d) [db] [dbm] – PL(d) [db]n -> path loss exponentn -> path loss exponent
dd00 -> reference distance close to transmitter -> reference distance close to transmitter
EnvironmentEnvironment nn
Free spaceFree space 22Urban area cellular radio Urban area cellular radio 2.7 – 3.52.7 – 3.5LOS in buildingLOS in building 1.6 – 1.81.6 – 1.8
PPRR(d) [dbm] = P(d) [dbm] = Ptt [dbm] – PL(d) [db] [dbm] – PL(d) [db]n -> path loss exponentn -> path loss exponent
dd00 -> reference distance close to transmitter -> reference distance close to transmitter
EnvironmentEnvironment nn
Free spaceFree space 22Urban area cellular radio Urban area cellular radio 2.7 – 3.52.7 – 3.5LOS in buildingLOS in building 1.6 – 1.81.6 – 1.8
5454
Log-Normal ShadowingLog-Normal ShadowingLog-Normal ShadowingLog-Normal Shadowing Log-distance path loss normal gives Log-distance path loss normal gives
only the average value of path loss.only the average value of path loss. Surrounding environment may be Surrounding environment may be
vastly different at two locations vastly different at two locations having the same T – R separation d.having the same T – R separation d.
Log-distance path loss normal gives Log-distance path loss normal gives only the average value of path loss.only the average value of path loss.
Surrounding environment may be Surrounding environment may be vastly different at two locations vastly different at two locations having the same T – R separation d.having the same T – R separation d.
5555
Log-Normal ShadowingLog-Normal ShadowingLog-Normal ShadowingLog-Normal ShadowingMore accurate model includes a random More accurate model includes a random variable to account for change in variable to account for change in environment. environment.
PL(d) [db] PL(d) [db] = PL(d) + X= PL(d) + X
= PL(d= PL(d00) + 10n log (d / d) + 10n log (d / d00) + X) + X
XX -> Zero mean Gaussian -> Zero mean Gaussian random variable (dB)random variable (dB)
-> Standard deviation (dB)-> Standard deviation (dB)
More accurate model includes a random More accurate model includes a random variable to account for change in variable to account for change in environment. environment.
PL(d) [db] PL(d) [db] = PL(d) + X= PL(d) + X
= PL(d= PL(d00) + 10n log (d / d) + 10n log (d / d00) + X) + X
XX -> Zero mean Gaussian -> Zero mean Gaussian random variable (dB)random variable (dB)
-> Standard deviation (dB)-> Standard deviation (dB)
5656
Received Power in Received Power in Log-Normal Shadowing Model Log-Normal Shadowing Model Received Power in Received Power in Log-Normal Shadowing Model Log-Normal Shadowing Model PPRR(d) [dbm] = P(d) [dbm] = PTT[dbm] – PL(d) [db][dbm] – PL(d) [db] Values of n and Values of n and are computed from are computed from
measured data.measured data. Linear regression method which Linear regression method which
minimizes the difference between minimizes the difference between measured and estimated path measured and estimated path
Estimated over a wide range of Estimated over a wide range of measurement locations and T – R measurement locations and T – R separations.separations.
PPRR(d) [dbm] = P(d) [dbm] = PTT[dbm] – PL(d) [db][dbm] – PL(d) [db] Values of n and Values of n and are computed from are computed from
measured data.measured data. Linear regression method which Linear regression method which
minimizes the difference between minimizes the difference between measured and estimated path measured and estimated path
Estimated over a wide range of Estimated over a wide range of measurement locations and T – R measurement locations and T – R separations.separations.
5757
...Received Power in ...Received Power in Log-Normal Shadowing ModelLog-Normal Shadowing Model...Received Power in ...Received Power in Log-Normal Shadowing ModelLog-Normal Shadowing Model
Probability [ PProbability [ PRR (d) > (d) > ] = ] =
Probability [ PProbability [ PRR (d) < (d) < ] = ] =
Probability [ PProbability [ PRR (d) > (d) > ] = ] =
Probability [ PProbability [ PRR (d) < (d) < ] = ] =
)(dPQ R
)(dPQ R
5858
ee xx22//22
zzxx
Calculation of Q FunctionCalculation of Q FunctionCalculation of Q FunctionCalculation of Q Function
Q(z) = Q function =
Q(-z) = 1- Q(z)
Q(0) = 1/ 2
Q(z) obtained from Appendix F,
Table F.1, page 647
Q(z) = Q function =
Q(-z) = 1- Q(z)
Q(0) = 1/ 2
Q(z) obtained from Appendix F,
Table F.1, page 647
dxex
z
x
2
2
2
1
5959
Calculation of Q FunctionCalculation of Q FunctionCalculation of Q FunctionCalculation of Q Function
6060
ExampleExampleExampleExample Four received power measurements Four received power measurements
were taken at the distances of were taken at the distances of 100m, 200m, 1 km and 3 km from a 100m, 200m, 1 km and 3 km from a transmitter. These measured values transmitter. These measured values are given in the following table.are given in the following table.
The path loss equation model for The path loss equation model for other measurements follows log other measurements follows log normal shadowing model where normal shadowing model where dd0 = 100 m. = 100 m.
Four received power measurements Four received power measurements were taken at the distances of were taken at the distances of 100m, 200m, 1 km and 3 km from a 100m, 200m, 1 km and 3 km from a transmitter. These measured values transmitter. These measured values are given in the following table.are given in the following table.
The path loss equation model for The path loss equation model for other measurements follows log other measurements follows log normal shadowing model where normal shadowing model where dd0 = 100 m. = 100 m.
6161
ExampleExampleExampleExampleA. Find the minimum mean square error
(MMSE) estimate for the path loss exponent n.
B. Calculate the standard deviation about the mean value.
C. Estimate the received power at d = 2 km using the resulting model.
D. Predict the likelihood that the received signal at 2 km will be greater than –60 dBm.
A. Find the minimum mean square error (MMSE) estimate for the path loss exponent n.
B. Calculate the standard deviation about the mean value.
C. Estimate the received power at d = 2 km using the resulting model.
D. Predict the likelihood that the received signal at 2 km will be greater than –60 dBm.
6262
Let Pi be the average received power at distance di
Pi (d) = Pi (d0) – 10n log (d /100)
d = d0 = 100m = > P0= 0 dBm
Let Pi be the average received power at distance di
Pi (d) = Pi (d0) – 10n log (d /100)
d = d0 = 100m = > P0= 0 dBm
Solution:Solution:Solution:Solution: T-R distanceT-R distance Measured PowerMeasured Power
100 m 100 m 0 dBm 0 dBm200 m200 m - 20 dBm - 20 dBm1 km1 km - 35 dBm - 35 dBm3 km3 km - 70 dBm - 70 dBm
T-R distanceT-R distance Measured PowerMeasured Power100 m 100 m 0 dBm 0 dBm200 m200 m - 20 dBm - 20 dBm1 km1 km - 35 dBm - 35 dBm3 km3 km - 70 dBm - 70 dBm
6363
A.A.A.A.dd11= 200 m, P= 200 m, P11= -3n, = -3n,
dd22= 1 km, P= 1 km, P33= -10n, = -10n,
dd33= 3 km, P= 3 km, P44= -14.77n= -14.77n
Mean square error J = Mean square error J = (P – P (P – Pii))22
= (0 – 0)= (0 – 0)22 + [-20 – (-3n)] + [-20 – (-3n)] 22
+ [-35 – (-10n)]+ [-35 – (-10n)] 22 + [-70 – (-14.77n)] + [-70 – (-14.77n)]
22
= 6525 – 2887.8n + 327.153n= 6525 – 2887.8n + 327.153n22
Minimum value = > dJ(n) / dnMinimum value = > dJ(n) / dn= 654.306n – 2887.8 = 0= 654.306n – 2887.8 = 0 n = 4.4n = 4.4
dd11= 200 m, P= 200 m, P11= -3n, = -3n,
dd22= 1 km, P= 1 km, P33= -10n, = -10n,
dd33= 3 km, P= 3 km, P44= -14.77n= -14.77n
Mean square error J = Mean square error J = (P – P (P – Pii))22
= (0 – 0)= (0 – 0)22 + [-20 – (-3n)] + [-20 – (-3n)] 22
+ [-35 – (-10n)]+ [-35 – (-10n)] 22 + [-70 – (-14.77n)] + [-70 – (-14.77n)]
22
= 6525 – 2887.8n + 327.153n= 6525 – 2887.8n + 327.153n22
Minimum value = > dJ(n) / dnMinimum value = > dJ(n) / dn= 654.306n – 2887.8 = 0= 654.306n – 2887.8 = 0 n = 4.4n = 4.4
6464
B.B.B.B.
Variance 2 = J / 4 = ( P – Pi)2 / 4
= (0= (0 ++ 0) + (-200) + (-20 +13.2)+13.2)22 + (-35 + (-35 ++ 44)44)22 + (-70 + (-70 ++ 64.988)64.988)22
4= 152.36 / 4 = 38.09
= 6.17 dB
Variance 2 = J / 4 = ( P – Pi)2 / 4
= (0= (0 ++ 0) + (-200) + (-20 +13.2)+13.2)22 + (-35 + (-35 ++ 44)44)22 + (-70 + (-70 ++ 64.988)64.988)22
4= 152.36 / 4 = 38.09
= 6.17 dB
6565
C.C.C.C.
Pi (d = 2 km)
= 0 – 10(4.4) log (2000/100)
= -57.24 dBm
Pi (d = 2 km)
= 0 – 10(4.4) log (2000/100)
= -57.24 dBm
6666
D.D.D.D.Probability that the received signal will be greater than –60 dBm is:
_____PR = [PR(d) > -60 dBm] = Q [(- PR (d)) / ]
= Q [(-60 + 57.24) / 6.17 ]= Q [- 0.4473]= 1 – Q [0.4473]= 1 – 0.326= 0.674 = > 67.4%
Probability that the received signal will be greater than –60 dBm is:
_____PR = [PR(d) > -60 dBm] = Q [(- PR (d)) / ]
= Q [(-60 + 57.24) / 6.17 ]= Q [- 0.4473]= 1 – Q [0.4473]= 1 – 0.326= 0.674 = > 67.4%
6767
Area AArea A
% of Coverage Area% of Coverage Area% of Coverage Area% of Coverage Area Given a circular Given a circular
coverage area coverage area of radius R...of radius R...
In the area A, the received power PR
The area A is defined as U()
Given a circular Given a circular coverage area coverage area of radius R...of radius R...
In the area A, the received power PR
The area A is defined as U()
r R
6868
Calculation of Coverage Area U(Calculation of Coverage Area U())Calculation of Coverage Area U(Calculation of Coverage Area U())
U (U () = (1 / ) = (1 / R R22 )) ƒ Prob [PProb [PRR (R) > (R) > ] dA ] dA
__________
Where Prob [PWhere Prob [PRR ( (RR) > ) > ] = Q [ ] = Q [ - P - PRR ( (RR) / ) / ] ]
U (U () = (1 / ) = (1 / R R22 )) ƒ Prob [PProb [PRR (R) > (R) > ] dA ] dA
__________
Where Prob [PWhere Prob [PRR ( (RR) > ) > ] = Q [ ] = Q [ - P - PRR ( (RR) / ) / ] ]
6969
Final Equation for U(Final Equation for U())Final Equation for U(Final Equation for U())
The error function erf(z) =
The error function erf(z) =
)2(21
2
0
2
zQ
ez
x
2
log102
)log(10)(
:
))]1(1()(1[
2
1)(
00
)21(2
enb
dR
ndPLP
a
whereb
aberfeaerfU
t
b
ab
7070
Alternate method: Use Fig. 4.18 (p 143)Alternate method: Use Fig. 4.18 (p 143)Alternate method: Use Fig. 4.18 (p 143)Alternate method: Use Fig. 4.18 (p 143)
7171
ExampleExampleExampleExampleFor the previous problem, For the previous problem, predict the percentage of area predict the percentage of area with a 2 km radius cell that with a 2 km radius cell that receives signals greater than receives signals greater than –60 dBm.–60 dBm.
For the previous problem, For the previous problem, predict the percentage of area predict the percentage of area with a 2 km radius cell that with a 2 km radius cell that receives signals greater than receives signals greater than –60 dBm.–60 dBm.
7272
SolutionSolutionSolutionSolutionFrom solution to previous example,From solution to previous example,
Prob [PProb [PR (R) > (R) > ] = 0.674 ] = 0.674 =>(=>( / n) = 6.17 / 4.4 / n) = 6.17 / 4.4
= 1.402= 1.402
From Figure 4.18, From Figure 4.18, Fraction of total area = 0.92 => 92%Fraction of total area = 0.92 => 92%
From solution to previous example,From solution to previous example,
Prob [PProb [PR (R) > (R) > ] = 0.674 ] = 0.674 =>(=>( / n) = 6.17 / 4.4 / n) = 6.17 / 4.4
= 1.402= 1.402
From Figure 4.18, From Figure 4.18, Fraction of total area = 0.92 => 92%Fraction of total area = 0.92 => 92%
7373
Other Propagation ModelsOther Propagation ModelsOther Propagation ModelsOther Propagation Models Outdoor propagation modelsOutdoor propagation models
Longley Rice model: Longley Rice model: point-to-point communication systems point-to-point communication systems (40MHz–100MHz)(40MHz–100MHz)
Okumara’s model: Okumara’s model: widely used in urban areas widely used in urban areas (150 MHz – 300 MHz)(150 MHz – 300 MHz)
Hata model: Hata model: graphical path lossgraphical path loss(150 MHz – 1500 MHz)(150 MHz – 1500 MHz)
Outdoor propagation modelsOutdoor propagation models Longley Rice model: Longley Rice model:
point-to-point communication systems point-to-point communication systems (40MHz–100MHz)(40MHz–100MHz)
Okumara’s model: Okumara’s model: widely used in urban areas widely used in urban areas (150 MHz – 300 MHz)(150 MHz – 300 MHz)
Hata model: Hata model: graphical path lossgraphical path loss(150 MHz – 1500 MHz)(150 MHz – 1500 MHz)
7474
Other Propagation ModelsOther Propagation ModelsOther Propagation ModelsOther Propagation Models Indoor propagation modelsIndoor propagation models
Log-distance path loss Log-distance path loss modelmodel
Ericsson multiple Ericsson multiple breakdown modelbreakdown model
Indoor propagation modelsIndoor propagation models Log-distance path loss Log-distance path loss
modelmodel Ericsson multiple Ericsson multiple
breakdown modelbreakdown model
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