Mobile Radio Propagation Large-Scale Path Loss

Mobile Radio Propagation Contents  Free space propagation  Basic Propagation models o Reflection o Diffraction o Scattering  Path Loss and Shadowing Models Wave Propagation  Radio, microwave, infrared and visible light portions of the spectrum can all be used to transmit information o By modulating the amplitude, frequency, or phase of the waves.  The amount of information a wireless channel can carry is related to its bandwidth  Wavelength dictates the optimum size of the receiving antenna Characteristics of Radio Waves  Easy to generate  Can travel long distances  Can penetrate buildings  Used for both indoor and outdoor communication  Can be narrowly focused at high frequencies (greater than 100MHz) using parabolic antennas (like satellite dishes)  Subject to interference from other radio wave sources Characteristics of Radio Waves (cont.) Properties of radio waves are frequency dependent  At low frequencies, they can pass through obstacles , but the power falls off sharply with increase in distance from the source  At high frequencies, they tend to travel in straight lines and bounce of obstacles (they can also be LOS path absorbed by rain)

Reflected Wave Communication Channels  Wired Channel o Stationary o Predictable  Wireless channel o Random o Typical to analyze o Susceptible to noise, interference, other time varying channel impairments Channel models for Wireless Communication  Physical models: Considers exact profile of the propagation environment. o Modes of propagation considered: Free-space or LOS, reflection, and diffraction.  Statistical models: Takes an empirical approach. o The model is developed on measuring propagation characteristics in a variety of environments. They are easy to describe and use than physical models. Need for Propagation models Propagations models can be used to determine  Coverage area of a transmitter  Transmit power requirement  Battery lifetime  Modulation and coding schemes required to improve the channel quality  Maximum achievable channel capacity of the system Propagation models Large-scale propagation models o Characterize signal strength for large T-R separation (several hundreds or thousands of meters) o Compute local average received power by averaging signal measurements over a track of 5  to 40  o Received signal decrease gradually o Useful for estimating the coverage area of transmitters Small-scale propagation models o Characterize rapid fluctuations in the received signal strength over very short travel distances (a few wavelengths) o Signal is the sum of many contributors coming from different directions. Thus phases of received signals are random and the sum behave like a noise (Rayleigh fading) o Received power may vary by as much as 3 or 4 orders of magnitude (30 or 40 dB) Small-Scale and Large-Scale Fading Free-Space Propagation Model  Predict the received signal strength when transmitter and receiver have clear, unobstructed LOS path between them. o Ex: Satellite communication system, microwave LOS system  The received power decays as a function of T-R separation raised to some power.  Free space power received by a receiver antenna is given by Friis free-space equation

2 2 2 푃푟(푑) = (푃푡퐺푡퐺푟휆 ) / ((4휋) 푑 퐿) o P (d) is the received power oPt is transmitted power r

oGt, Gr is the Tx, Rx antenna gain o d is T-R separation distance in meters (dimensionless quantity) o  is wavelength in meters oL is system loss factor not related to propagation (퐿 ≥ 1). L = 1 indicates no loss in system hardware (we consider L = 1 in our calculations) Free-Space Propagation Model (cont.) 2  The gain of an antenna G is related to its affective aperture Ae by G = 4Ae /  where

o Ae is related to the physical size of the antenna

o  is related to the carrier frequency ( = c/f = 2c / c ) where o f is carrier frequency in Hertz o c is speed of light in meters/sec

o c is carrier frequency in radians per second  Isotropic radiator generally considered an reference antenna in wireless systems; radiates power with unit gain uniformly in all directions.  Effective isotropic radiated power (EIRP) is the amount of power that a theoretical isotropic antenna emits to produce peak power density in the direction of maximum antenna gain.

EIRP = PtGt  Antenna gains are given in units of dBi (dB gain with respect to an isotropic antenna) What is Decibel (dB)  A logarithmic unit used to describe a ratio between two values of a physical quantity (usually measured in units of power or intensity) oThe ratio of two values 푃1 and 푃2 in dB is 10 log (푃1/푃2) dB oExample: 푃1 = 100 푊 and 푃2 = 1 푊 The ratio is 10 log(100/1) = ퟐퟎ 풅푩  dB unit is generally used to describe ratios of numbers with modest size. dBm  Indicates power ratio in dB with 1mW as the reference power  Example: Transmit power = 100푊 in dBm is Transmit power (dBm) = 10 log(100 푊 / 1 푚푊) = 10 log(100,000) = 50 푑퐵푚  Similarly

1 mW = 0 dBm 1 W = 30 dBm 10 W = 40 dBm 100 W = 50 dBm 106 W = 90 dBm dBW  Indicates power ratio in dB with 1 푊 as the reference power level.  Example: Transmit power = 100 푊 in dBW is Transmit power (푑퐵푊) = 10 log(100푊 / 1푊) = 10 log 100 = 20 푑퐵푊  Similarly

1 mW = -30 dBm 1 W = 0 dBm 10 W = 10 dBm 100 W = 20 dBm 106 W = 60 dBm Free-Space Path Loss  Path loss is defined as the difference (in dB) between the effective transmitted power and the received power  Free-space path loss is defined as the path loss of the free-space model 2 2 2 푃퐿(푑퐵) = 10 푙표푔(푃푡/푃푟) = −10 푙표푔[(퐺푡퐺푟휆 )/(4휋) 푑 ]  Friis equation holds when distance 푑 is in the far-field of the transmitting antenna  The far-field or Fraunhofer region of a transmitting antenna is defined as the region beyond the far-field distance 푑푓 given by: 2 o 푑푓 = 2퐷 /휆 , 퐷 is the largest physical dimension of the antenna o Additionally 푑푓 >> 퐷 푎푛푑 푑푓 >> 휆 Reference Distance, 푑0  Friis free space eq. does not hold for 푑 = 0

 Received power reference point, 푑0 is used 푑푓 ≤ 푑0 ≤ 푑 푑0 should be smaller than any practical distance a mobile system uses  The power received in free space at a distance greater than d0 is 푛 Pr(푑) = Pr(푑0)(푑0/푑) where 푑푓 ≤ 푑0 ≤ 푑

 Reference distance d0 for practical systems: o For frequncies in the range 1 to 2 GHz  1 m in indoor environments  100 m to 1 km in outdoor environments Radio propagation mechanisms

Source: Radio Frequency and Wireless Communications - Scientific Figure on Research Gate Source: https://physicsweekly.weebly.com/uploads/2/5/8/4/25849299/6320607.jpg?332 Reflection  Reflection occurs when wave impinges upon an obstruction much larger in size compared to the wavelength of the signal o Example: reflections from earth and buildings  Reflected waveform may interfere with the original signal constructively or destructively Reflection (cont.)

 When a radio wave propagating in one medium impinges upon another medium having different electrical properties, the wave is partially reflected and partially transmitted oPerfect dielectric: Part of the energy is transmitted into the second medium and part of the energy is reflected back into the first medium no loss of energy in absorption oPerfect conductor:  All incident energy is reflected back into the first medium  No loss of energy.  The fraction that is reflected is described by the Fresnel equation and is dependent upon the incoming light's polarization and angle of incidence. Reflection (cont.)  EM waves are transmitted in two orthogonal dimensions, referred to as polarizations. Two commonly used orthogonal sets of polarizations are o Horizontal and Vertical polarization Vertical polarization is commonly used in terrestrial mobile radio communication. In VHF band, vertical polarization produces a higher field strength near the ground. Also, mobile antennas for vertical polarization are more robust and convenient to implement. o Left-hand and right-hand circular polarization Often used in satellite communication. Can be used together for well-designed communication links to double the transmission capacity in a given frequency band. Ground Reflection (Two-Ray) Model In a mobile radio channel, a single direct path between the BS and a mobile is seldom the only physical means for propagation and the Free space propagation model is inaccurate in most cases when used alone. Two-ray model is  Based on geometric optics and it considers both the direct path and a ground reflected propagation path  Reasonably accurate for predicting the large scale signal strength over distances of several kilometers for mobile radio systems that use tall towers. Ground Reflection Model (cont.)

 The total received E-field, ETOT is a result of the direct LOS component 퐸퐿푂푆 and the ground reflected component 퐸푟 퐸 퐸 + 퐸푟 푇푂푇 = 퐿푂푆 Ground Reflection Model (cont.)  Using the method of images, path difference between LOS and ground reflected path can be calculated.

 For 푑 ≫ ℎ푡 + ℎ푟, path difference Δ is 2ℎ ℎ Δ = 푑′′ − 푑′ ≈ 푡 푟 푑

 Phase difference 휃∆ between the two E-field components and the time delay between arrival of the two components is 2휋∆ 4휋ℎ ℎ 휃 = ≈ 푡 푟 ∆ 휆 푑휆 Ground Reflection Model (cont.)

 For large distance 푑 ≫ ℎ푡ℎ푟 ℎ2ℎ2 푃 = 푃 퐺 퐺 푡 푟 푟 푡 푡 푟 푑4 The received power falls off with distance raised to the fourth power, or at a rate of 40 dB/decade  This is much more rapid path loss than expected due to free space Diffraction  Diffraction occurs when radio wave is obstructed by an impenetrable body or a surface with sharp irregularities (edges)  Due to bending of radio waves it enables communication between devices with no line-of-sight path Diffraction (cont.)  Secondary waves are present throughout the space including the space behind the obstacle due to bending of waves around the obstacle.  Enables communication even when a line of sight path does not exist between transmitter and receiver.  At high frequencies, diffraction depends on the geometry of the object, as well as the amplitude, phase and polarization of the incident wave at the point of diffraction Diffraction Huygens’ Principal

 All points on a wavefront can be considered as point sources for producing secondary wavelets  Secondary wavelets combine to produce new wavefront in the direction of propagation  Diffraction arises from propagation of secondary wavefront into shadowed area  Field strength of diffracted wave in shadow region =  electric field components of all secondary wavelets in the space around the obstacle Diffraction (cont.)

 Consider a transmitter-receiver pair in free space  Obstacle of effective height h with infinite width is placed between Tx and Rx o distance from transmitter = d1 o distance from receiver = d2  LOS distance between transmitter & receiver is 푑 = 푑1 + 푑2 Diffraction (cont.)  Excess Path Length is the difference between the direct and the diffracted path Δ = Δ푑 – (푑1 + 푑2), where Δ푑 = Δ푑1 + Δ푑2 2 2 Δ푑푖 = ℎ + 푑푖  Thus, excess path length is

2 2 2 2 Δ = ℎ + 푑1 + ℎ + 푑2 − 푑1 + 푑2

 Assuming ℎ << 푑1 , 푑2 and ℎ >> 휆, then by substitution and Taylor Series Approximation ℎ2 푑 + 푑 Δ ≈ 1 2 2 푑1푑2  Phase difference, ϕ 2휋Δ 2휋 ℎ2 푑 + 푑 휋 2(푑 + 푑 ) 휙 = ≈ 1 2 = ℎ2 1 2 휆 휆 2 푑1푑2 2 휆푑1푑2 Diffraction Fresnel zones  Fresnel-Kirchoff Diffraction Parameter 푣 (dimensionless) characterizes phase difference between the two propagation paths is defined as 2(푑 + 푑 ) 2푑 푑 푣 = ℎ 1 2 = 훼 1 2 휆푑1푑2 휆(푑1 + 푑2) where ℎ refers to the height of the obstruction and 훼 is in radians. Phase difference, 휙 is given as 휋 휙 = 푣2 2  The phase difference between LOS and diffracted path is function of o obstruction’s height & position o transmitters and receivers height and position Diffraction Fresnel zones (cont.)  Fresnel Zones explains the concept of diffraction loss as a function of path difference.  Secondary waves in successive regions have a path length 푛/2 greater than LOS path. o nth region is the region where path length of secondary waves is n/2 greater than that of LOS path length Source:  Regions form a series of ellipsoids https://upload.wikimedia.org/wikipedia/commons/4/4b/ with foci at Tx & Rx antennas 1st_Fresnel_Zone_Avoidance.png Diffraction Fresnel zones (cont.)

2(d  d ) 2d d v = h 1 2   1 2 d1d2 (d1  d2 )

TX RX d 1 d2 d1 h d2 TX RX  If h = 0, then  and v are 0

If  and v are negative, then h is negative Diffraction Fresnel zones (cont.) On slicing a specific ellipsoid along the plane perpendicular to LOS yields a circle with radius rn given as R 푛휆푑1푑2 ℎ = 푟푛 = 푑1 + 푑2 then Kirchoff diffraction parameter is given as T

2(푑 + 푑 ) 푛휆푑 푑 2(푑 + 푑 ) 푣 = ℎ 1 2 = 1 2 1 2 = 2푛 휆푑1푑2 푑1 + 푑2 휆푑1푑2 Thus, for given 푣 defines an ellipsoid with constant excess path  = 푛/2 . Diffraction Fresnel zones (cont.) 1st Fresnel Zone is volume enclosed by the first ellipsoid.  2푛푑 Fresnel Zone is volume enclosed between first and the second ellipsoid.  At receiver, the contribution to the electric field from the successive  Phase Difference, Δ pertaining to 푛th Fresnel Zones will be in phase Fresnel Zone is opposition and therefore will interfere 2 n  h d1  d2  destructively rather than constructively.      2  2 d1d2  Diffraction Fresnel zones (cont.)

Source: http://www.cdt21.com/resources/Java_file/Applet2/pk_FresnelZoneE/fresnelzone01e.gif Diffraction Diffraction Loss Diffraction Loss is caused by blockage of secondary (diffracted) waves  Partial energy from secondary waves is diffracted around an obstacle oobstruction blocks energy from some of the Fresnel zones and only a portion of transmitted energy reaches receiver  Received energy is vector sum of contributions from all unobstructed Fresnel zones o depends on geometry of obstruction o phase of secondary (diffracted) E-field is indicated by the Fresnel Zones  Obstacles may block transmission paths causing diffraction loss oconstruct a family of ellipsoids between TX & RX to represent Fresnel zones 휆 ojoin all points for which excess path delay is multiple of 2 ocompare geometry of obstacle with Fresnel zones to determine diffraction loss (or gain) Diffraction Diffraction Loss (cont.) Place ideal, perfectly straight screen between Tx and Rx  If top of screen is well below LOS path then screen will have little effect o the Electric field at Rx = 퐸퐿푂푆 (free space value)  As screen height increases, Electric  If (55 to 60)% of 1st Fresnel zone is field will vary as screen blocks more clear than further Fresnel zone Fresnel zones clearing does not significantly alter  The amplitude of oscillation diffraction loss increases until the screen is just in line  For free-space transmission with Tx and Rx conditions,1st Fresnel Zone is kept ofield strength = ½ of unobstructed unblocked field strength Diffraction Knife Edge Diffraction Model  Diffraction Losses o estimating attenuation caused by diffraction over obstacles is essential for predicting field strength in a given service area o not possible to estimate losses precisely o theoretical approximations typically corrected with empirical measurements  Computing Diffraction Losses o for simple terrain: expressions have been obtained o for complex terrain: computing diffraction losses is complex Huygens secondary Diffraction source Knife Edge Diffraction Model (cont.)  Knife-edge model is the simplest model that provides insight about magnitude of diffraction loss o Diffraction losses are estimated using the classical Fresnel solution for field behind a knife edge o Useful for shadowing caused by 1 knife edge object  Considers receiver R is located in shadowed region  E-field strength at R is vector sum of all fields due to secondary Huygens’ sources in the plane above the knife edge Diffraction Knife Edge Diffraction Model (cont.) The diffraction gain due to the presence of knife edge, as compared to the free space E-field Diffraction Knife Edge Diffraction Model (cont.) Diffraction Multiple Knife-Edge Diffraction Model Bullington's model o with more than one obstruction: compute total diffraction loss o replace multiple obstacles with one equivalent obstacle o use single knife edge model Disadvantage: o oversimplifies problem o often produces overly optimistic estimates of received signal strength Scattering  Scattering occurs when obstacle size is less than or of the order of the wavelength of propagating wave  Causes the transmitter energy to be radiated in many directions  Occur due to small objects, rough surfaces, and other irregularities of the channel. For example: Lamp posts and street, etc.  Number of obstacles are quite large  Scattering follows same principles as diffraction Scattering (cont.)  Received signal strength is often stronger than that predicted by reflection/diffraction models alone  The EM wave incident upon a rough or complex surface is scattered in many directions and provides more energy at a receiver  Energy that would have been absorbed is instead reflected to the receiver o flat surface → EM reflection (one direction) o rough surface → EM scattering (many directions) Scattering (cont.)  Critical height for surface protuberances ℎ푐 for given incident angle 휃푖 휆 ℎ푐 = 8 sin 휃푖  Let ℎ be the maximum protuberances, then surface is considered o smooth if ℎ < ℎ푐 o rough if ℎ > ℎ푐 Reflection, Diffraction, and Scattering As a mobile moves through a region, these mechanisms have an impact on the instantaneous received signal strength o In case LOS path exists between the devices, diffraction and scattering will not dominate the propagation. oIf device is at a street level without LOS path, then diffraction and scattering will probably dominate the propagation. Path Loss Models  Radio Propagation models are derived using a combination of empirical and analytical methods.  These methods implicitly take into account all the propagation factors both known and unknown through the actual measurements.  Path loss models are used to estimate the received signal level as a function of distance.  With the help of this model we can predict SNR for a mobile communication system.  Path loss estimation techniques o Log - Distance Path Loss Model o Log - Normal Shadowing Path Loss Models Log-distance path loss model  Average large scale path loss is  d    PL(dB)  PL(d0 ) 10nlog   d0 

 PL is ensemble average of all possible path loss values for given value of d  On log-log scale path loss is a straight line with slope equal to 10 n dB/decade Path Loss Models (cont.) Path loss exponent for different environments Path Loss Models (cont.) Path Loss Models Log-Normal Shadowing Model  Log normal o If 푌 is Gaussian RV and 푍 is defined such that 푌 = log 푍, then 푍 is log- normal RV Shadowing o Also called slow-fading o Accounts for random variations in received power observed over distances comparable to the widths of buildings o Extra transmit power (a fading margin) must be provided to compensate for these fades  Surrounding environment clutter may be vastly different at two different locations having same T-R separation Path Loss Models Log-Normal Shadowing Model (cont.)  PL(d) is random and log-normally distributed about the mean distance- dependent value  d    PL(d)  PL(d)  X   PL(d0 ) 10nlog   X  d0  푋휎: zero-mean Gaussian distributed random variable (in dB) with standard deviation 휎  The probability that received signal level exceed a certain value 훾 is    P (d)  Pr[P (d)   ]  Q r  r       P (d)    The probability that received signal level is below 훾 is Pr[P (d)   ]  Q r  r      Path Loss Models Outdoor Propagation  We will look to the propagation characteristics of the three outdoor environments o Propagation in macrocells o Propagation in microcells o Propagation in street microcells Outdoor Propagation Macrocells  Base stations at high-points  Coverage of several kilometers  The average path loss in dB has normal distribution o Average path loss is a result of forward scattering over a large number of obstacles each contributing a random multiplicative factor. On changing to dB, it is a sum of random variables o Sum is normally distributed because of central limit theorem Outdoor Propagation Longley-Rice Propagation Prediction Model  Point-to-point communication in frequency range 40 MHZ to 100GHz  Also referred as irregular terrain model (ITM)  Predicts median transmission loss, takes terrain into account, uses path geometry, calculates diffraction losses  Inputs of computer program of Longley-Rice model : o Frequency o Path length o Polarization and antenna heights o Surface refractivity o Effective radius of earth o Ground conductivity o Ground dielectric constant o Climate Outdoor Propagation Longley-Rice Propagation Prediction Model (cont.)  Computer program operates on path specific parameters  Disadvantages o Does not take into account details of terrain near the receiver o Does not consider Buildings, Foliage, Multipath  Original model modified by Okamura for urban terrain (include extra term called urban factor) Outdoor Propagation Okumura Model  In early days, the models were based on emprical studies  Okumura did comprehesive measurements in 1968 and came up with a model. oDiscovered that a good model for path loss was a simple power law where the exponent 푛 is a function of the frequency, antenna heights, etc. o It is one of the most widely used models for signal prediction in urban areas, oValid for frequencies in: 150 MHz – 1920 MHz for distances: 1km – 100km Outdoor Propagation Okumura Model (cont.)

퐿50(푑)(푑퐵) = 퐿퐹(푑) + 퐴푚푢(푓, 푑) – 퐺(ℎ푡푒) – 퐺(ℎ푟푒) – 퐺퐴푅퐸퐴 o 퐿50: 50th percentile (i.e. median) of o 퐺퐴푅퐸퐴: gain due to different type of path loss environment o 퐿퐹(푑): free space propagation pathloss o ℎ푡푒: transmitter antenna height o 퐴푚푢(푓, 푑): median attenuation relative o ℎ푟푒: receiver antenna height to free space 퐺 ℎ푡푒 and 퐺 ℎ푟푒 are determined for o 퐺(ℎ푡푒): base station antenna height different antenna height gain factor o 퐺(ℎ푟푒): mobile antenna height gain factor Outdoor Propagation Okumura Model (cont.) Outdoor Propagation Okumura Model (cont.)  Advantage o Okumuras’ model is considered to be among the simplest and best in terms of accuracy in path loss prediction for mature cellular and land mobile system in a cluttered environment.  Disadvantage o Low response to rapid changes in terrain Outdoor Propagation Hata Model  Empirical formulation of the graphical path loss data provided by Okumura  Valid from 150 MHz to 1500 MHz For urban areas the formula is

퐿 푢푟푏푎푛, 푑 푑퐵 = 69.55 + 26.16 log 푓푐 − 13.82 log ℎ푡푒 – 푎 ℎ푟푒 + 44.9 – 6.55 log ℎ푡푒 log 푑

o fc is the ferquency in MHz o d is T-R separation in km

o hte is effective transmitter antenna o a(hre) is the correction factor for effective height in meters (30-200m) mobile antenna height which is a function of coverage area (different for o hre is effective receiver antenna height in meters (1-10 m) large and medium city) Outdoor Propagation Hata Model (cont.)  For small to medium sized city:  For large city:

 In sub urban areas, path loss is:  In open rural areas, path loss is: Outdoor Propagation Hata Model (cont.)  No path specific corrections  Suitable for large cell mobile system (d >1 km)  Not suitable for PCS Outdoor Propagation PCS Extension of Hata Model  Higher frequencies: up to 2 GHz  Smaller cell sizes  Lower antenna heights  For 푑 = 1 to 20 km 퐿 푑퐵 = 46.3 + 33.9 log 푓푐 − 13.82 log ℎ푡푒 – 푎 ℎ푟푒 + 44.9 – 6.55 log ℎ푡푒 log 푑 + 퐶푚 where 퐶푚 = 0 and 3 dB for medium and metro city, respectively Path Loss Models Microcells

 Propagation differs significantly o Milder propagation characteristics o Small multipath delay spread and shallow fading imply the feasibility of higher data-rate transmission o Mostly used in crowded urban areas o If transmitter antenna is lower than the surrounding building than the signals propagate along the streets: Street Microcells Path Loss Models Macrocells versus Microcells

Item Macrocell Microcell

Cell Radius 1 to 20km 0.1 to 1km

Tx Power 1 to 10W 0.1 to 1W

Fading Rayleigh Nakgami-Rice

RMS Delay Spread 0.1 to 10s 10 to 100ns

Max. Bit Rate 0.3 Mbps 1 Mbps

69 Path Loss Models Street Microcells  Most of the signal power propagates along the street  The signals may reach with LOS paths if the receiver is along the same street with the transmitter  The signals may reach via indirect propagation mechanisms if the receiver turns to another street Path Loss Models: Street Microcells D Building Blocks

B C A Breakpoint

received power (dB) received power (dB) A A n=2 B n=2 Breakpoint 15~20dB

C n=4 n=4~8 D log (distance) Indoor Propagation  Indoor channels are different from traditional mobile radio channels in two different ways: o The distances covered are much smaller o The variablity of the environment is much greater for a much smaller range of T-R separation distances.  The propagation inside a building is influenced by: o Layout of the building o Construction materials o Building type: sports arena, residential home, factory, etc Path Loss Models Indoor Propagation  Indoor path loss models are less generalized o Environment comparatively more dynamic  Significant features are physically smaller o Smaller propagation distances  Less assurance of Far-field for all receiver locations and antenna types. o More clutter, scattering, less LOS Path Loss Models Indoor Propagation (cont.)  Indoor propagation is domited by the same mechanisms as outdoor: reflection, scattering, diffraction. o However, conditions are much more variable  Doors/windows open or not  The mounting place of antenna: desk, ceiling, etc.  The level of floors  Indoor channels are classified as o Line-of-sight (LOS) o Obstructed (OBS) with varying degrees of clutter. Path Loss Models Indoor Propagation (cont.)  Buiding types o Residential homes in suburban areas o Residential homes in urban areas o Traditional office buildings with fixed walls (hard partitions) o Open plan buildings with movable wall panels (soft partitions) o Factory buildings o Grocery stores o Retail stores o Sport arenas Indoor propagation Events and parameters  Temporal fading for fixed and moving terminals oMotion of people inside building causes Ricean Fading for the stationary receivers oPortable receivers experience in general:  Rayleigh fading for obstructed propagation paths  Ricean fading for LOS paths.  Multipath Delay Spread o Buildings with fewer metals and hard-partitions typically have small rms delay spreads: 30-60ns.  Can support data rates excess of several Mbps without equalization o Larger buildings with great amount of metal and open aisles may have rms delay spreads as large as 300ns.  Can not support data rates more than a few hundred Kbps without equalization. Indoor propagation Models  Log-distance path loss model  Same floor partition losses oHard partitions (cannot be moved) /soft partitions (can be moved) oInternal walls & external walls  Partition loss between floors oDetermined by the dimensions/materials used/surroundings, including number of windows) /floor attenuation  Ericsson multiple breakpoint model oObtained by measurements in a multiple office building oHas 4 breakpoints and has upper & lower bound on the PL oModel assumes 30 db attenuation at do=1m, for f=900Mhz, unity gain antenna

References [1] T. S. Rappaport, Wireless Communications: Principles and Practice (2nd edition), Pearson Education, 2010. [2] S. Haykin and M. Moher, Modern Wireless Communications, Pearson Education, 2005.