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Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
Mobile Radio Propagation
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Mobile Radio Propagation

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  • 1. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 1Chapter 3Mobile Radio Propagation
  • 2. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 2Outline Speed, Wavelength, Frequency Types of Waves Radio Frequency Bands Propagation Mechanisms Radio Propagation Effects Free-Space Propagation Land Propagation Path Loss Fading: Slow Fading / Fast Fading Delay Spread Doppler Shift Co-Channel Interference The Near-Far Problem Digital Wireless Communication System Analog and Digital Signals Modulation Techniques
  • 3. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 3Speed, Wavelength, FrequencySystem Frequency WavelengthAC current 60 Hz 5,000 kmFM radio 100 MHz 3 mCellular 800 MHz 37.5 cmKa band satellite 20 GHz 15 mmUltraviolet light 1015Hz 10-7mLight speed = Wavelength x Frequency= 3 x 108m/s = 300,000 km/s
  • 4. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 4Types of WavesTransmitter ReceiverEarthSky waveSpace waveGround waveTroposphere(0 - 12 km)Stratosphere(12 - 50 km)Mesosphere(50 - 80 km)Ionosphere(80 - 720 km)
  • 5. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 5Radio Frequency BandsClassificationBandInitials Frequency Range CharacteristicsExtremely low ELF < 300 HzGround waveInfra low ILF 300 Hz - 3 kHzVery low VLF 3 kHz - 30 kHzLow LF 30 kHz - 300 kHzMedium MF 300 kHz - 3 MHz Ground/SkywaveHigh HF 3 MHz - 30 MHz Sky waveVery high VHF 30 MHz - 300 MHzSpace waveUltra high UHF 300 MHz - 3 GHzSuper high SHF 3 GHz - 30 GHzExtremely high EHF 30 GHz - 300 GHzTremendously high THF 300 GHz - 3000 GHz
  • 6. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 6Propagation Mechanisms Reflection Propagation wave impinges on an object which is large ascompared to wavelength- e.g., the surface of the Earth, buildings, walls, etc. Diffraction Radio path between transmitter and receiverobstructed by surface with sharp irregular edges Waves bend around the obstacle, even when LOS (line of sight)does not exist Scattering Objects smaller than the wavelength of thepropagation wave- e.g. foliage, street signs, lamp posts
  • 7. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 7Radio Propagation EffectsTransmitterdReceiverhbhmDiffractedSignalReflected SignalDirect SignalBuilding
  • 8. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 8Free-space Propagation The received signal power at distance d:where Pt is transmitting power, Ae is effective area, and Gt is thetransmitting antenna gain. Assuming that the radiated power is uniformlydistributed over the surface of the sphere.Transmitter Distance dReceiverhbhm2r4PdPGA tteπ=
  • 9. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 9Antenna Gain For a circular reflector antennaGain G = η ( π D / λ )2η = net efficiency (depends on the electric field distribution over theantenna aperture, losses, ohmic heating , typically 0.55)D = diameterthus, G = η (π D f /c )2, c = λ f (c is speed of light)Example: Antenna with diameter = 2 m, frequency = 6 GHz, wavelength = 0.05 mG = 39.4 dB Frequency = 14 GHz, same diameter, wavelength = 0.021 mG = 46.9 dB* Higher the frequency, higher the gain for the same size antenna
  • 10. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 10Land Propagation The received signal power:where Gr is the receiver antenna gain,L is the propagation loss in the channel, i.e.,L = LP LS LFLPGGP trtr =Fast fadingSlow fadingPath loss
  • 11. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 11Path Loss (Free-space) Definition of path loss LP :Path Loss in Free-space:where fc is the carrier frequency.This shows greater the fc , more is the loss.,rtPPPL =),(log20)(log2045.32)( 1010 kmdMHzfdBL cPF ++=
  • 12. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 12Path Loss (Land Propagation) Simplest Formula:Lp = A d-αwhereA and α: propagation constantsd : distance between transmitter and receiverα : value of 3 ~ 4 in typical urban area
  • 13. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 13Example of Path Loss (Free-space)Path Loss in Free-space7080901001101201300 5 10 15 20 25 30Distance d (km)PathLossLf(dB)fc=150MHzfc=200MHzfc=400MHzfc=800MHzfc=1000MHzfc=1500MHz
  • 14. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 14Path Loss (Urban, Suburban and Open areas) Urban area:where Suburban area: Open area:[ ][ ] )(log)(log55.69.44)()(log82.13)(log16.2655.69)(10101010kmdmhmhmhMHzfdBLbmbcPU−+−−+= α[ ][ ] [ ][ ][ ]≥−≤−−−−=citymediumsmallforMHzfformhMHzfformhcityelforMHzfmhMHzfmhcmcmcmcm&,400,97.4)(75.11log2.3200,1.1)(54.1log29.8arg,8.0)(log56.1)(7.0)(log1.1)(2102101010α4.528)(log2)()(210 −−=MHzfdBLdBL cPUPS[ ] 94.40)(log33.18)(log78.4)()( 10210 −+−= MHzfMHzfdBLdBL ccPUPO
  • 15. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 15Path Loss Path loss in decreasing order: Urban area (large city) Urban area (medium and small city) Suburban area Open area
  • 16. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 16Example of Path Loss (Urban Area: Large City)Path Loss in Urban Area in Large City1001101201301401501601701800 10 20 30Distance d (km)PathLossLpu(dB)fc=200MHzfc=400MHzfc=800MHzfc=1000MHzfc=1500MHzfc=150MHz
  • 17. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 17Example of Path Loss(Urban Area: Medium and Small Cities)Path Loss in Urban Area for Small & Medium Cities1001101201301401501601701800 10 20 30Distance d (km)PathLossLpu(dB)fc=150MHzfc=200MHzfc=400MHzfc=800MHzfc=1000MHzfc=1500MHz
  • 18. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 18Example of Path Loss (Suburban Area)Path Loss in Suburban Area901001101201301401501601700 5 10 15 20 25 30Distance d (km)PathLossLps(dB)fc=150MHzfc=200MHzfc=400MHzfc=800MHzfc=1000MHzfc=1500MHz
  • 19. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 19Example of Path Loss (Open Area)Path Loss in Open Area80901001101201301401500 5 10 15 20 25 30Distance d (km)PathLossLpo(dB)fc=150MHzfc=200MHzfc=400MHzfc=800MHzfc=1000MHzfc=1500MHz
  • 20. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 20FadingSignalStrength(dB)DistancePath LossSlow Fading(Long-term fading)Fast Fading(Short-term fading)
  • 21. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 21Slow Fading The long-term variation in the mean level is known as slow fading(shadowing or log-normal fading). This fading caused by shadowing. Log-normal distribution:- The pdf of the received signal level is given in decibels bywhere M is the true received signal level m in decibels, i.e., 10log10m,M is the area average signal level, i.e., the mean of M,σ is the standard deviation in decibels( )( ),21 222σσπMMeMp−−=
  • 22. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 22Log-normal DistributionMM2σp(M)The pdf of the received signal level
  • 23. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 23Fast Fading The signal from the transmitter may be reflected fromobjects such as hills, buildings, or vehicles. When MS far from BS, the envelope distribution of received signalis Rayleigh distribution. The pdf iswhere σ is the standard deviation. Middle value rm of envelope signal within sample range to besatisfied by We have rm = 1.777( ) 0,2222>=−rerrprσσ.5.0)( =≤ mrrP
  • 24. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 24Rayleigh DistributionThe pdf of the envelope variationr2 4 6 8 10P(r)00.20.40.60.81.0σ=1σ=2σ=3
  • 25. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 25Fast Fading (Continued) When MS far from BS, the envelope distribution ofreceived signal is Rician distribution. The pdf iswhereσ is the standard deviation,I0(x) is the zero-order Bessel function of the first kind,α is the amplitude of the direct signal( ) 0,022222≥=+−rrIerrprσασσα
  • 26. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 26Rician DistributionrPdfp(r)r864200.60.50.40.30.20.10α = 2α = 1α= 0 (Rayleigh)σ = 1α = 3The pdf of the envelope variation
  • 27. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 27Characteristics of Instantaneous Amplitude Level Crossing Rate: Average number of times per second that the signalenvelope crosses the level in positive goingdirection. Fading Rate: Number of times signal envelope crosses middlevalue in positive going direction per unit time. Depth of Fading: Ratio of mean square value and minimum value offading signal. Fading Duration: Time for which signal is below given threshold.
  • 28. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 28Doppler Shift Doppler Effect: When a wave source and a receiver are moving towardseach other, the frequency of the received signal will not be the same as thesource. When they are moving toward each other, the frequency of the received signalis higher than the source. When they are opposing each other, the frequency decreases.Thus, the frequency of the received signal iswhere fC is the frequency of source carrier,fD is the Doppler frequency. Doppler Shift in frequency:where v is the moving speed,λ is the wavelength of carrier.θλcosvfD =DCR fff −=MSSignalMovingspeed v
  • 29. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 29Delay Spread When a signal propagates from a transmitter to areceiver, signal suffers one or more reflections. This forces signal to follow different paths. Each path has different path length, so the time ofarrival for each path is different. This effect which spreads out the signal is called“Delay Spread”.
  • 30. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 30Moving Speed EffectTimeV1 V2 V3 V4Signalstrength
  • 31. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 31Delay SpreadDelaySignalStrength The signals fromclose by reflectorsThe signals fromintermediate reflectorsThe signals fromfar away reflectors
  • 32. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 32Intersymbol Interference (ISI) Caused by time delayed multipath signals Has impact on burst error rate of channel Second multipath is delayed and is receivedduring next symbol For low bit-error-rate (BER) R (digital transmission rate) limited by delayspread τd.dRτ21<
  • 33. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 33Intersymbol Interference (ISI)TimeTimeTimeTransmissionsignalReceived signal(short delay)Received signal(long delay)101Propagation timeDelayed signals
  • 34. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 34Coherence Bandwidth Coherence bandwidth Bc: Represents correlation between 2 fading signalenvelopes at frequencies f1 and f2. Is a function of delay spread. Two frequencies that are larger than coherencebandwidth fade independently. Concept useful in diversity receptionMultiple copies of same message are sent usingdifferent frequencies.
  • 35. Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved. 35Cochannel Interference Cells having the same frequency interfere with each other. rd is the desired signal ru is the interfering undesired signal β is the protection ratio for whichrd ≤ βru (so that the signals interfere the least) If P(rd ≤ βru ) is the probability that rd ≤ βru ,Cochannel probability Pco = P(rd ≤ βru )

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