Radio Spread.


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What is Radio? Radio Xmitter actuates E&M fields. Electrostatic field segments 1/d3 ... Common and man-made radio impedance... What does the field look ...
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Slide 1

Radio Propagation CSCI 694 24 September 1999 Lewis Girod

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Outline Introduction and phrasing Propagation components Propagation models Radio Propagation

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What is Radio? Radio Xmitter impels E&M fields Electrostatic field parts µ 1/d 3 Induction field segments µ 1/d 2 Radiation field segments µ 1/d Radiation field has E and B segment Field quality at separation d = E  B µ 1/d 2 Surface range of circle focused at transmitter Radio Propagation

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General Intuition Two fundamental components influencing signal at beneficiary Distance (or postpone)  Path constriction Multipath  Phase contrasts Green sign ventures 1/2  more remote than Yellow to achieve collector, who sees Red . For 2.4 GHz,  (wavelength) =12.5cm. Radio Propagation

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Objective Invent models to anticipate what the field looks like at the recipient. Constriction, retention, reflection, diffraction... Movement of collector and environment… Natural and man-made radio impedance... What does the field look like at the recipient? Radio Propagation

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Models are Specialized Different scales Large scale (arrived at the midpoint of over meters) Small scale (request of wavelength) Different ecological qualities Outdoor, indoor, land, ocean, space, and so on. Diverse application ranges macrocell (2km), microcell(500m), picocell Radio Propagation

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Outline Introduction and some phrasing Propagation Mechanisms Propagation models Radio Propagation

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Radio Propagation Mechanisms Free Space proliferation Refraction Conductors & Dielectric materials (refraction) Diffraction Fresnel zones Scattering "Mess" is little in respect to wavelength Radio Propagation

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Free Space Assumes far-field (Fraunhofer area) d >> D and d >>  , where D is the biggest direct measurement of recieving wire  is the transporter wavelength No impedance, no checks Radio Propagation

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Free Space Propagation Model Received force at separation d is the place P t is the transmitter power in Watts a steady variable K relies on upon reception apparatus pick up, a framework misfortune component, and the bearer wavelength Radio Propagation

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Refraction Perfect channels reflect with no weakening Dielectrics mirror a small amount of episode vitality "Nibbling points" reflect max* Steep edges transmit max* q r q t Reflection instigates 180  stage shift Radio Propagation *The careful division relies on upon the materials and frequencies included

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T R first Fresnel zone Obstruction Diffraction happens when waves hit the edge of a deterrent "Optional" waves engendered into the shadowed locale Excess way length results in a stage shift Fresnel zones relate stage movements to the positions of impediments Radio Propagation

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Fresnel Zones Bounded by curved loci of consistent deferral Alternate zones contrast in stage by 180  Line of sight (LOS) compares to first zone If LOS is incompletely blocked, second zone can ruinously meddle (diffraction misfortune) Path 1 Path 2 Fresnel zones are circles with the T&R at the foci; L 1 = L 2 + l Radio Propagation

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Power Propagated into Shadow How much influence is spread along these lines? first FZ: 5 to 25 dB beneath free space prop. LOS 0 - 10 - 20 - 30 - 40 - 50 - 60 0 o 90 180 o dB Obstruction Rappaport, pp. 97 Tip of Shadow first second Obstruction of Fresnel Zones  Radio Propagation

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Scattering Rough surfaces basic stature for knocks is f( ,incident edge) dissipating misfortune component demonstrated with Gaussian dispersion. Adjacent metal articles (road signs, and so forth.) Usually displayed factually Large far off items Analytical model: Radar Cross Section ( RCS ) Radio Propagation

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Outline Introduction and some phrasing Propagation Mechanisms Propagation models Large scale proliferation models Small scale spread (blurring) models Radio Propagation

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Propagation Models: Large scale models anticipate conduct arrived at the midpoint of over separations >>  Function of separation & critical natural elements, generally recurrence autonomous Breaks down as separation declines Useful for demonstrating the scope of a radio framework and unpleasant scope quantification Radio Propagation

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Propagation Models: Small scale (blurring) models portray signal variability on a size of  Multipath impacts (stage cancelation) rule, way constriction considered steady Frequency and transfer speed subordinate Focus is on demonstrating "Blurring": quick change in sign over a short separation or time allotment. Radio Propagation

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Large Scale Models Path misfortune models Outdoor models Indoor models Radio Propagation

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Free Space Path Loss Path Loss is a measure of constriction construct just with respect to the separation to the transmitter Free space show just legitimate in far-field; Path misfortune models commonly characterize a "nearby in" point d 0 and reference different focuses from that point: What is dB? Radio Propagation

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Log-Distance Path Loss Model Log-separation sums up way misfortune to represent other natural elements Choose a d 0 in the far field. Measure PL(d 0 ) or ascertain Free Space Path Loss. Take estimations and determine  experimentally. Radio Propagation

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Log-Distance 2 Value of  portrays distinctive situations Rappaport, Table 3.2, pp. 104 Radio Propagation

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Log-Normal Shadowing Model Shadowing happens when items square LOS amongst transmitter and beneficiary A basic factual model can represent capricious "shadowing" Add a 0-mean Gaussian RV to Log-Distance PL Markov model can be utilized for spatial connection Radio Propagation

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Outdoor Models "2-Ray" Ground Reflection model Diffraction model for sloping landscape Radio Propagation

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T R h t h r Phase shift! 2-Ray Ground Reflection For d >> h r h t , low point of occurrence permits the earth to go about as a reflector the reflected sign is 180  out of stage P r  1/d 4 (=4) Radio Propagation

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T R p 0 h t h r p 1 Ground Reflection 2 Intuition: ground pieces first Fresnel zone Reflection causes a prompt 180  stage shift Additional stage balance because of overabundance way length If the subsequent stage is still near 180 , the gound beam will dangerously meddle with the LOS beam. 180  Radio Propagation

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Hilly Terrain Propagation can be LOS or aftereffect of diffraction more than one or more edges LOS spread demonstrated with ground reflection: diffraction misfortune But in the event that there is no LOS, diffraction can really offer assistance! Radio Propagation

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Indoor Path Loss Models Indoor models are less summed up Environment similarly more dynamic Significant components are physically littler Shorter separations are nearer to close handle More mess, disseminating, less LOS Radio Propagation

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Indoor Modeling Techniques Modeling systems and methodologies: Log-Normal, <2 for LOS down hall Log-Normal shadowing model if no LOS Partition and floor weakening variables Computationally concentrated "beam following" taking into account 3-D model of building and constriction elements for materials Radio Propagation

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Outline Introduction and some phrasing Propagation Mechanisms Propagation models Large scale spread models Small scale proliferation (blurring) models Radio Propagation

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Recall: Fading Models Small scale (blurring) models portray signal variability on a size of  Multipath impacts (stage cancelation) overwhelm, way lessening considered consistent Frequency and transfer speed subordinate Focus is on demonstrating "Blurring": quick change in sign over a short separation or time span. Radio Propagation

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Factors Influencing Fading Motion of the beneficiary: Doppler shift Transmission data transmission of sign Compare to BW of channel Multipath proliferation Receiver sees numerous examples of sign when waves take after various ways Very delicate to setup of environment Radio Propagation

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Effects of Multipath Signals Rapid change in sign quality because of stage cancelation Frequency adjustment because of Doppler movements from development of collector/environment Echoes created by multipath engendering delay Radio Propagation

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h(t,  )  The Multipath Channel One way to deal with little scale models is to show the "Multipath Channel" Linear time-fluctuating capacity h(t, ) Basic thought: characterize a channel that exemplifies the impacts of multipath impedance Measure or ascertain the channel motivation (reaction to a short heartbeat at f c ): t Radio Propagation

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SKIP Channel Sounding " Channel sounding " is an approach to quantify the channel reaction transmit drive, and measure the reaction to discover h(  ). h(  ) can then be utilized to display the channel reaction to a self-assertive sign: y(t) = x(t) h( ). Issue: models the divert at single point in time; can\'t represent portability or ecological changes h(t,  )  Radio Propagation

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Characterizing Fading * *Adapted from EE535 Slides, Chugg \'99 From the motivation reaction we can describe the channel: Characterizing twisting Delay spread (  d ) : to what extent does the channel ring from a drive? Intelligence data transmission (B c ): over what recurrence reach is the channel increase level?  d 1/B c In time space , generally compares to the "loyalty" of the reaction; more keen heartbeat requires more extensive band Radio Propagation

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Effect of Delay Spread * For a framework with bw W and image time T... Does the channel contort the sign? in the event that W << B c : " Flat Fading " Amplitude and stage mutilation just if W > B c : " Frequency Selective Fading " If T <  d , between image obstruction (ISI) happens For narrowband frameworks (W  1/T), FSF 

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