Research Article Determination of Measurement Points in ...

Research ArticleDetermination of Measurement Points in UrbanEnvironments for Assessment of Maximum Exposure toEMF Associated with a Base Station

Agostinho Linhares Antonio Joseacute Martins Soares and Marco Antonio Brasil Terada

Antenna Group Electrical Engineering Department University of Brasilia 70910-900 Brasılia DF Brazil

Correspondence should be addressed to Agostinho Linhares linharesfilhogmailcom

Received 28 March 2014 Revised 10 July 2014 Accepted 14 July 2014 Published 8 September 2014

Academic Editor Panayiotis Frangos

Copyright copy 2014 Agostinho Linhares et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

A base station (BS) antenna operates in accordancewith the established exposure limits if the values of electromagnetic fields (EMF)measured in points of maximum exposure are below these limits In the case of BS in open areas the maximum exposure to EMFprobably occurs in the antennarsquos boresight direction from a few tens to a few hundred meters away This is not a typical sceneryfor urban environments However in the line of sight (LOS) situation the region of maximum exposure can still be analyticallyestimated with good results This paper presents a methodology for the choice of measurement points in urban areas in order toassess compliance with the limits for exposure to EMF

1 Introduction

The mobile communications technology has revolutionizedthe telecommunications industry worldwide over the last twodecades In order to attend the demand of users of cellularservices a substantial growth has been observed in both theamount of BS and the number of available frequency bandsInternational bodies have established EMF exposure limitsfor personal protection [1 2] that are endorsed by WorldHealth Organization (WHO) [3] as well as measurementstandards to assess the compliance of radio communicationstations with the exposure limits [4]

Three basic components have to be taken into accountwhen evaluating human exposure to EMF radio frequency(RF) source wireless channel and exposed person The firstconsiders technical characteristics of the radiating systemlike radiated power antenna gain height tilt and half-powerangle The second is related to the path loss consideringthat the wave propagates in an uncontrolled and lossymedium and is subject to variations not only due to distancebetween EMF source and exposed person but also due toshadowing andmultipath [5]The third component is relatedto characteristics of the exposed person including but not

limited to height weight and position (standing up sittingdown lying etc)

It is worth noting that EMF exposure and coverageprediction deal with the propagation phenomena Neverthe-less the human exposure to EMF is a quite different issuecompared with the coverage problem given that the relevantregion of the former is in the vicinity of the station wherehigher power density levels can be measured Therefore theselection of measurement points located in the region ofmaximum exposure due to the BS being evaluated is veryimportant to guarantee compliance with EMF exposure limit

For practical reference level assessment in far field regionmeasurement of derived quantities like electric field intensitymagnetic field intensity or power density are sufficient toensure that the basic restrictions are satisfied [2]

This paper presents amethodology to estimate the proba-ble location of maximum exposure to EMF associated with aBS antenna in urban areas as well as suburban or rural areasfilling a gap not covered by current international standards[6ndash8] which address selection of points of investigationwithout covering how to identify locations of maximumexposure In [9] an approach was developed based on openarea modeling including simulations and measurements in

Hindawi Publishing CorporationInternational Journal of Antennas and PropagationVolume 2014 Article ID 297082 7 pageshttpdxdoiorg1011552014297082

2 International Journal of Antennas and Propagation

such type of environment The present work improves andgeneralizes the previous methodology so that it could besuitable for any environment including paths with slopes forLOS condition

The remainder of this work is structured as follows InSection 2 we present an overview of urban environments andtraditional propagation models are revisited In Section 3 wepresent the methodology of how to select points of investi-gation based on chances of maximum exposure In Section 4the proposed methodology is tested using simulation andmeasurement results Finally in Section 5 some conclusionremarks are presented

2 Propagation Models

For proper evaluation of the path loss of radio waves thepropagation models should adequately consider the maincharacteristics that impact the wireless system such asfrequency antenna height and the environment (terrainbuilding vegetation LOS NLOS etc)

Urban areas are more complex than open areas scenariosin relation to the RF presenting multiple objects in theenvironment that produce reflected diffracted or scatteredreplicas of the original signal In these cases the free-spacepropagation model overestimates the real exposure levelbesides complex environments enhance nonuniform fielddistribution along an exposed person once those replicasreach the human body with different amplitudes phases andtime delays

Figure 1 shows a typical scenario of the set RF sourcewireless channel and person exposed Point 119875

1(building

rear) is reached with the maximum radiation intensity direc-tion part of the energy is reflected andpartwill penetrate andpass through the building being both refracted and absorbedin a multilayer environment Part of the signal will passthrough the building and reach 119872

1and 119872

2 The absorbed

wave may be more relevant at 1198721than 119875

2and 119875

3diffracted

waves However at certain distance the diffracted signalbecomes predominant for instance at 119872

2 The 119872

3person

will be reached by a direct ray combined with reflected (1198753

and 1198754) and scattered components (119875

5) Basically shadowing

is the effect of diffraction while multipath is the effect ofreflection and scattering

Multipath (or small-scale) fading creates nonuniformfield distribution along human bodyTherefore performing aspatial averaging process is highly recommended for a whole-body assessment [5] It must be noted that spatial averagingfor the purpose of human exposure to EMF is performed byaveraging the electric field intensity squared and then takingsquare root of the result or by averaging the power densitySpatial averaging of the electric field intensity will result inhigher values compared with simple averaging

The combination of path loss and shadowing can bewritten as

PL (119889119861) = 119860 + 10120574 log( 119889

1198890

) + 119904 (1)

where119860 and 120574 can be function of one ormore of the followingparameters frequency antenna height and environment 119889

P1

P2

P3

P4

P5

M3

M2

M1

Figure 1 Representation of the main propagation mechanisms in acomplex environment LOS reflection diffraction absorption andscattering

is the distance from the antenna 1198890is a reference distance

in the same unit of 119889 the shadow (or large-scale) fadingparameter 119904 is a zero-mean Gaussian random variable withstandard deviation 120590 [10] Nevertheless it can be assumedthat the spatial variations at a local scale are only due tosmall-scale fading [11] For instance for the free-space model119860 = 324+20sdotlog(119891) where119891 is frequency in GHz 119889

0= 1m

and 120574 = 2If the path loss follows (1) then the average power density

in Wm2 can be estimated using the following generalizedformula

119878 (119889 120579 0) =119875 sdot 119866max sdot 119865 (120579 0)

119870 sdot 119889120574 (2)

where 119875 is the power supplied to the antenna in 119882 119866maxis the maximum gain of the antenna 119865(120579 120601) is the relativenumerical gain varying with elevation and azimuth angles119870is a fix value for the specific considered model 120574 is the pathloss exponentThe influence of 119865(120579 120601) for NLOS is studied in[12]

21 The Two-Ray Propagation Model The two-ray modelconsiders that between the EMF source and the receiver thereare just the direct ray and a single specular reflected ray thatdominates the multipath effect The direct ray propagatesthrough free space and the reflected ray is proportional to thedirect electric field intensity by a complex factor Γ (reflectioncoefficient) With this model the nonuniform distributionalong the whole body can be shown mainly for ultrahighfrequencies (UHF) or above

For a fast and conservative estimation of the powerdensity it is common to consider that the reflected ray is in-phase with the direct ray so that the power density can becalculated as

119878 (119889 120579 0) =(1 + |Γ|)

2sdot 119875 sdot 119866max sdot 119865 (120579 0)

4 sdot 120587 sdot 1198892 (3)

International Journal of Antennas and Propagation 3

where |Γ| is the modulus of the ground reflection coefficient(a typical value is 06)

22 Walfisch-Ikegami Model Line of Sight Scenario COST-Wal-fisch-Ikegami model (COST-WI model) takes intoaccount more information to describe the urban environ-ment like height and separation of buildings widths ofstreets and street orientation with respect to the direct radiopathThismodel distinguishes between LOS andNLOS caseswhere the EMF source and the receiver are within a streetcanyon in the former case This formulation is based onmeasurements performed in Stockholm Sweden [13]

For the LOS COST-WI model 119860 = 426 + 20 sdot log(119891)and 120574 = 26 This model is suitable for use over the ranges of800ndash2000MHz height of base station antenna (119867) between4 and 50m height of mobile antenna (ℎ) in range of 1ndash3mand 20m le d le 5000m

Considering the relationship between the equivalentisotropically radiated power (EIRP) and the power receivedby an isotropic antenna it is possible to estimate the powerdensity at the receiving point in scenarios that follow LOSCOST-WI model as (see Appendix)

119878 (119889 120579 0) =119875 sdot 119866max sdot 119865 (120579 0)

20811988926 (4)

It should be noted that the exponent in (4) is the samepath loss exponent 120574 while the value 208 is associated withthe parameter 119860

23 Other Models Reference [14] verified that for their LOSmeasurements the results were very close to free space withaverage path loss decaying as 119889minus2 Therefore for these cases120574 = 2 and 119870 = 4120587 Reference [15] also identified 120574 close to2 in rural areas (21 for receiving antenna at 10m and 27 forreceiving antenna at 6m)

Other path loss propagation models like Hata ECC-33and SUI can also be written in the form PL = 119860+10sdot120574sdotlog(119889)with some correction or gain factors being added

All these complex models present better results for NLOSand typically overestimate path loss for LOS environments Ingeneral LOS presents 120574 asymp 2 (26 for LOS COST-WI) whileNLOS presents 120574 between 3 and 5

3 Methodology for Determination ofMeasurement Points

In [9] an approach was developed based on open area mod-eling including simulations and measurements in such typeof environment The present work improves and generalizesthe previous methodology so that it could be suitable for anyLOS condition including paths with slopes

It is quite clear that the maximum exposure region islikely to occur parallel to the antenna boresight for open areacases Nevertheless depending on the antenna installationand technical characteristics the main lobe might not beresponsible for maximum exposure point but the sidelobes[16] On the other hand as the maximum exposure may belocated some hundreds of meters away the BS chances are

Figure 2 Simulation of a BS located in downtown of Sao PauloBuildings in both sides of the streets block the EMF propagationHowever directions with fewer blockages present stronger EMFsignals even for back radiation of the antenna

Figure 3 A tridimensional view of the BS among densely tallbuildings Antenna height is 30m azimuth is 0∘ tilt is 10∘ andhalf-power angle is 88∘ and 26∘ for horizontal and vertical planesrespectively EIRP = 1000W and 119891 = 900MHz

that buildings constructionsmight obstruct the LOS in urbanenvironmentTherefore not only positions in the direction ofthe antennarsquos boresight are relevant but also other positionswith LOS to the antenna may be a point of interest

Figure 2 illustrates a simulation in downtown of SaoPaulo Brazil where just one sector of the BS is presentedin order to evaluate the single source influence It must benoted that the antenna azimuth is 0∘ north the crossingstreet orientation is approximately 35∘ and there are hugebuildings in 3 of 4 corners as shown in Figure 3 In thiscase relevant maximum exposure points will occur not inthe direction of the antennarsquos boresight but according to theorientation of crossing streets that have LOS with the BSThesimulation tool used is ICS Telecom V12 Radio Planning andTechnical SpectrumManagement software [17] configured torun propagationmodel based on ITU-R Rec 525 calculationof free-space attenuation and Rec P526 propagation bydiffraction

The tridimensional radiation pattern 119865(120579 120601) can beapproximated by 119865(120579) sdot 119865(120601) where 119865(120579) and 119865(120601) arevertical and horizontal radiation patterns respectively Thisis a good approximation for the forward radiation and asufficient approximation for the backward radiation whichis satisfactory from the point of view of exposure assessment


x

x

asymp120573

120573

(a) (b)

Figure 4 Approximation of a sloped path by a plane pathwith tilted antenna (b) is not exactly equivalent to (a) because the119910-axis should alsobe rotated by 120573 degrees However the error introduced by this assumption is small compared to the estimated maximum exposure location

[18] The main lobe of 119865(120579) can be approximated by cos119902(120579 minus120572) where 120572 is the antenna tilt [9]

A BS antenna operates in accordance with the establishedexposure limits if the values of EMF measured in pointsof maximum exposure are below these limits Additionalmeasurement points may be required but the proposedmethodology provides guidelines on how to judiciously selectthe necessarymeasurement location that is the regionwherethe antenna main lobe reaches the exposed person in a LOScase Reference [16] showed that in some cases side lobescan be responsible formaximum exposure even transportingless energy Nevertheless it is very unlikely that any EMFexposure problem will happen in these cases

The estimated maximum power density location can becalculated substituting 119889 = [119909

2+ (119867 minus ℎ)

2]12 in (2) where

119909 is the horizontal distance from the BS to a reference point119867 is the antenna height and ℎ is the approximate head levelheight Taking 119889119878119889119909 = 0 and isolating 119909 we obtain

119909 = 119883expmax

= (radic[(119867 minus ℎ) sdot 119905119892120572 sdot (1 +119902

120574)]

2

+4 sdot 119902 sdot (119867 minus ℎ)

2

120574

minus (119867 minus ℎ) sdot 119905119892120572 sdot (1 +119902

120574)) times 05

(5)

where 119902 = log(12) log[cos(120579bw2)] and 120579bw is the half-power angle in the vertical plane Consequently 119883exp

max isa reference measurement point since it is likely that themaximum exposure location is near this point

The impact of street inclination (120573) in 119883expmax can be

mitigated by adequately addingsubtracting 120573 to the antennatilt 120572 turning the sloped path a plane region as presented inFigure 4 The error introduced by this assumption in the 119909-axis is ℎ sdot sin120573 which is much less than 119883exp

max Therefore (5)can be applied for these cases with adequate correction in 120572generating a 1205721015840

0

1

2

3

4

5

6

0 50 100 150Horizontal distance (m)

Pow

er d

ensit

y (m

Wm

2)

Figure 5 Power density evaluated based on ICS Telecom simula-tions The simulated maximum exposure point is located at 75msame as estimated for 120574 = 2 and higher than estimated for 120574 = 26

4 Testing the Proposed Methodology

Three urban areas cases are presented to test the methodol-ogy The first case considers the site of Figures 2 and 3 Thetechnical characteristics of the BS are presented in Table 1as well as the results for different 120574 values and simulationFigure 5 shows that the simulated and calculated maximumexposure locations are compatibleThe resultmatched the 120574 =2 due to the propagation model selected in the simulationthat is free space combined with diffraction

The second case considers path loss propagation mea-surements at 910MHz made in downtown core of OttawaCanada using transmissions from an antenna at 85m heightto a receiving antennamounted on a van at 365mheight [19]The author conducted LOS andNLOSmeasurements in areaswith buildings taller than the antennas in both street sidesbut just LOS measurement in the westward of Slater Street isconsidered for testing the proposed approach

The transmitter and receiver antennas are omnidirec-tional and the elevation discrimination was discounted so


Table 1 BS 1mdashSao Paulo

Technical parametersAntenna height (119867) 30mReference height (ℎ) 15mVertical 3-dB angle 256∘

Horizontal 3-dB angle 88∘

Tilt (120572) 10∘ (mechanical)EIRP 1000W (60 dBm)

ResultsCalculated 119883exp

max 75m 120574 = 2

Calculated 119883expmax 68m 120574 = 26

Simulated119883expmax 75m

55

60

65

70

75

80

85

90

95

20 200

Path

loss

(dB)

Distance (m)MeasLSFS

Figure 6 Path loss westward of the transmitter located at 300 SlaterStreet In this case the PL = 234 + 266 log(119889) with 120590 = 384was obtained using least square (LS) regression analysis and thencompared with free space (FS) The intercept point between bothmodels is 18m

the presented results are just path loss which were recoveredfrom the graphical curves presented in [19] The receivedpower was sampled approximately once per meter with acalibrated receiver

The resulting path loss is shown in Figure 6 Based on asimple linear regression analysis a path loss model is givenby

PL = 234 + 266 log (119889) (6)

where 119889 is the distance in meter and 1198890= 1m

It can be seen that the proposedmodel is very close to LOSCOST-WImodel given by PL = 238+26 log(119889) at 910MHz119889 in meters and 119889

0= 1m

Using the formulation presented in the Appendix thepower density can be estimated by

119878 (119889 120579 0) =119875 sdot 119866max sdot 119865 (120579 0)

189 sdot 119889266 (7)

Table 2 BS 2mdash300 Slater StreetmdashOttawa

Technical parametersAntenna height (119867) 115mReference height (ℎ) 15mAntenna model CommScope CV3PX308R1Vertical 3-dB angle 105∘


Tilt (120572) 5∘ (electrical)EIRP 10W (40 dBm)

ResultsCalculated119883exp

max 56m 120574 = 266

Calculated119883expmax 61m 120574 = 2

Simulated119883expmax 56m for estimated PL

Simulated119883expmax 62m for free space

Table 3 BS 3mdashAarhusDenmark

Technical parametersAntenna height (119867) 23mReference height (ℎ) 25mAntenna gain (dBi) 16Vertical 3-dB angle 54∘


Tilt (120572) 6∘ 10∘

Street slope (120573) asymp38∘

Transmitter max power 2 times 46 dBmResults

Calculated119883expmax 120574 = 2

1205721015840= 98∘

1205721015840= 138

∘

116m 79m


1205721015840= 98∘

1205721015840= 138

∘

113m 78mMeasured119883exp

max for 1205721015840= 98∘ 107m (movave)101m (peak)

Measured119883expmax for 120572

1015840= 138

∘ 67m (movave)76m (peak)

Simulations with the proposed path loss model and free-spacemodelwere executed following procedures used in [20]as presented in Figure 7 The BS has the technical character-istics presented in Table 2 As expected the simulated andcalculated maximum exposure locations are equal or veryclose

The third case uses [12] data collected in a measurementcampaign performed in the centre of Aarhus an urbanmedium city in Denmark with average building heightabout 15ndash18m and street width about 20m The technicalcharacteristics of the BS are presented in Table 3 as wellas the results for different 120574 values and simulation Basedon GPS collected data and Google Earth path profile theaverage street slope is approximately 38∘ within a 100 metersradius from the BS (Sector 1 of [12]) The receiver was avan with a 5 dBi omnidirectional antenna with ground planeat 25m height and a network scanner The sampling ratewas 50 sampless for an average driving speed of 15 kmhOf course the maximum received power point is the sameas the maximum power density point In the present workno correction for receiving vertical antenna pattern was


0

500

1000

1500

0 20 40 60 80 100Horizontal distance (m)

Free spacePL = 234 + 266 log d

Pow

er d

ensit

y (120583

Wm

2)

Figure 7 Power density depending on the distance119909 from the BS ascomputed with the free-spacemodel and the case specific PLmodelIt is being considered that PL below the intercept point at 18m isequivalent to free-space propagation

0 50 100 150 200d (m)

Moving averageMeasured

minus100

minus80

minus60

minus40

minus20

0

P(R

SRP)

(dBm

)

Figure 8 Reference signal received power (RSRP) of a 20MHz LTEsignal for antenna tilt of 10∘

used therefore only measurement farther than 20m wasconsidered in order to minimize its influence Figures 8 and9 show that the expected maximum exposure locations arecoherent with the proposed methodology

As it was shown in the cases of study the estimatedlocation 119883

expmax indicates the probable region of local maxi-

mum exposure Nevertheless it must be taken into accountthat scattered and diffracted fields may shift the real localmaximum exposure closer to or farther from the radio com-munication station Besides there are uncertainties related tothe exact BS technical information as well as GPS altitudesto estimate street slopes and results are sensible for theseparameters Therefore a procedure of walk around theestimated location measuring the electric field intensity mustbe performed to identify the point of maximum exposureSpatial averaging might be used when appropriate

0 50 100 150 200 250d (m)

MeasuredMoving average

P(R

SRP)

(dBm

)

minus100

minus80

minus60

minus40

minus20

0

Figure 9 RSRP of a 20MHz LTE signal for antenna tilt of 6∘

5 Conclusion

This paper presented a methodology to estimate the probablelocation of maximum exposure to EMF associated with a BSantenna in any environment for LOS cases filling a gap notcovered by current international standards

The results of the proposed methodology are consistentwith the presented case studies and previous work ForLOS scenarios the estimated maximum exposure location isdependent of path loss exponent 120574 but its influence does notplay major role for short distances as maximum exposurepoint is usually located in vicinity of the base station belowfew hundreds of meters

Results show that higher 120574 brings maximum exposurelocation closer to the base station Results suggest that incase of urban environmentwith canyon streets characteristicsand LOS technical staff should consider 120574 = 26 for areference point and then walking around the estimatedlocation measuring the electric field intensity to identify thereal maximum exposure point

Results also suggest that in other LOS cases technical staffshould consider 120574 = 2 for a reference point knowing thatthere are more chances to have maximum exposure locationcloser to the base station without disregarding the walkingaround measurement procedure

NLOS cases are likely to present low power density levelsfor human exposure concerns although it would providesatisfactory signal level for mobile communications There-fore when selecting measurement points for EMF exposureassessment LOS places should be preferable compared withNLOS locations

Appendix

This Appendix demonstrates how the parameter 119870 (2) canbe evaluated based on the path loss model The receivedpower of an ideally isotropic antenna (0 dBi) is given by

119875119877=EIRP119871

=119875 sdot 119866max sdot 119865 (120579 0)

119871 (A1)


where 119871 = 10119871dB10 and 119871

119889119861= PL at distance 119889 The received

power density is

119878 =119875119877

119860eff=

EIRP119870 sdot 119889120574

(A2)

where 119860eff = 12058224120587

Applying (A1) in (A2) it is possible to calculate119870 as

119870 =119860eff sdot 119871

119889120574 (A3)

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors thank I Rodriguez PhD from Aalborg Univer-sity for providing collected data (case 3) U Dias PhD and LCarısio PhD for their useful comments and Mr Y Robledofor supporting the simulations with ICS Telecom This workwas partially supported by DPPUnB (Dean of Research andGraduate StudiesmdashUnB)

References

[1] ldquoIEEE C951-2005mdashSafety levels with respect to humanexposure to radio frequency electromagnetic fields 3 kHZ to300GHzrdquo httpstandardsieeeorggetieeeC95downloadC951-2005pdf

[2] ICNIRP Guidelines for limiting exposure to time-varyingelectric magnetic and electromagnetic fields (up to 300GHz)httpwwwicnirporgdocumentsemfgdlpdf

[3] ldquoWorld Health OrganizationmdashInternational EMF Projectrdquohttpwwwwhointpeh-emfen

[4] World Health Organization ldquoFramework for DevelopingHealth-Based EMF Standardsrdquo httpwwwwhointpeh-emfstandardsframeworken

[5] A Linhares A J M Soares and U S Dias ldquoOn the small-scale fading evaluation in human exposure assessmentrdquo inProceedings of the SBMOIEEE MTTS International Microwaveand Optoelectronics Conference (IMOC rsquo13) Rio de JaneiroBrazil 2013

[6] ldquoDetermination of RF field strength and SAR in the vicinity ofradiocommunication base stations for the purpose of evaluatinghuman exposurerdquo IEC 62232 ed10 2011

[7] ITU-T Recommendation K-91 Guidance for assessment eval-uation and monitoring of human exposure to radio frequencyelectromagnetic fields 2012

[8] CENELEC EN 504002006 ldquoBasic standard to demonstratethe compliance of fixed equipment for radio transmission(110MHzndash40GHz) intended for use in wireless telecommu-nication networks with the basic restrictions or the referencelevels related to general public exposure to radio frequencyelectromagnetic fields when put into servicerdquo 2006

[9] A Linhares M A B Terada and A J M Soares ldquoEstimatingthe location of maximum exposure to electromagnetic fieldsassociated with a radiocommunication stationrdquo Journal ofMicrowaves Optoelectronics and Electromagnetic Applicationsvol 12 no 1 pp 141ndash157 2013

[10] V Erceg L J Greenstein S Y Tjandra et al ldquoEmpirically basedpath loss model for wireless channels in suburban environ-mentsrdquo IEEE Journal on Selected Areas in Communications vol17 no 7 pp 1205ndash1211 1999

[11] E Larcheveque C Dale M Wong and J Wiart ldquoAnalysisof electric field averaging for in situ radiofrequency exposureassessmentrdquo IEEE Transactions onVehicular Technology vol 54no 4 pp 1245ndash1250 2005

[12] I RodriguezHCNguyen T B Sorensen et al ldquoA geometrical-based vertical gain correction for signal strength prediction ofdowntilted base station antennas in urban areasrdquo in Proceedingsof the 76th IEEE Vehicular Technology Conference (VTC rsquo12)September 2012

[13] COST Action 231 ldquoDigital mobile radio towards future genera-tion systemsrdquo Final Report European Communities 1999

[14] I Rodriguez H C Nguyen and N T K Joslashrgensen ldquoPath lossvalidation for urban micro cell scenarios at 35 GHz comparedto 19 GHzrdquo in Proceedings of the IEEE Global CommunicationsConference (Globecom rsquo13) 2013

[15] V S Abhayawardhana I J Wassellt D Crosby M P Sellarsand M G Brown ldquoComparison of empirical propagation pathloss models for fixed wireless access systemsrdquo in Proceedings ofthe IEEE 61st Vehicular Technology Conference (VTC rsquo05) vol 1pp 73ndash77 June 2005

[16] A Linhares A J M Soares and M A B Terada ldquoSidelobes from radio base station antenna in the evaluation ofhuman exposure to EMFrdquo in Proceedings of the SBMOIEEEMTTS International Microwave and Optoelectronics Conference(IMOC) Rio de Janeiro Brazil 2013

[17] ldquoATDI Advanced RadiocommunicationsICS Telecom V12mdashRadio Planning and Technical Spectrum Management soft-warerdquo httpwwwatdicomics-telecom

[18] ITU-T Recommendation K-70mdashmitigation techniques to limithuman exposure to EMFs in the vicinity of radiocommunica-tion stations 2007

[19] J H Whitteker ldquoMeasurements of path loss at 910 MHz forproposed microcell urban mobile systemsrdquo IEEE Transactionson Vehicular Technology vol 37 no 3 pp 125ndash129 1988

[20] P H S Wanderley and M A B Terada ldquoAssessment of theinfluence of real-world radio station antennasrdquo The BrazilianJournal of Biomedical Engineering vol 27 pp 45ndash51 2011

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such type of environment The present work improves andgeneralizes the previous methodology so that it could besuitable for any environment including paths with slopes forLOS condition

The remainder of this work is structured as follows InSection 2 we present an overview of urban environments andtraditional propagation models are revisited In Section 3 wepresent the methodology of how to select points of investi-gation based on chances of maximum exposure In Section 4the proposed methodology is tested using simulation andmeasurement results Finally in Section 5 some conclusionremarks are presented

2 Propagation Models

For proper evaluation of the path loss of radio waves thepropagation models should adequately consider the maincharacteristics that impact the wireless system such asfrequency antenna height and the environment (terrainbuilding vegetation LOS NLOS etc)

Urban areas are more complex than open areas scenariosin relation to the RF presenting multiple objects in theenvironment that produce reflected diffracted or scatteredreplicas of the original signal In these cases the free-spacepropagation model overestimates the real exposure levelbesides complex environments enhance nonuniform fielddistribution along an exposed person once those replicasreach the human body with different amplitudes phases andtime delays

Figure 1 shows a typical scenario of the set RF sourcewireless channel and person exposed Point 119875

1(building

rear) is reached with the maximum radiation intensity direc-tion part of the energy is reflected andpartwill penetrate andpass through the building being both refracted and absorbedin a multilayer environment Part of the signal will passthrough the building and reach 119872

1and 119872

2 The absorbed

wave may be more relevant at 1198721than 119875

2and 119875

3diffracted

waves However at certain distance the diffracted signalbecomes predominant for instance at 119872

2 The 119872

3person

will be reached by a direct ray combined with reflected (1198753

and 1198754) and scattered components (119875

5) Basically shadowing

is the effect of diffraction while multipath is the effect ofreflection and scattering

Multipath (or small-scale) fading creates nonuniformfield distribution along human bodyTherefore performing aspatial averaging process is highly recommended for a whole-body assessment [5] It must be noted that spatial averagingfor the purpose of human exposure to EMF is performed byaveraging the electric field intensity squared and then takingsquare root of the result or by averaging the power densitySpatial averaging of the electric field intensity will result inhigher values compared with simple averaging

The combination of path loss and shadowing can bewritten as

PL (119889119861) = 119860 + 10120574 log( 119889

1198890

) + 119904 (1)

where119860 and 120574 can be function of one ormore of the followingparameters frequency antenna height and environment 119889

P1

P2

P3

P4

P5

M3

M2

M1

Figure 1 Representation of the main propagation mechanisms in acomplex environment LOS reflection diffraction absorption andscattering

is the distance from the antenna 1198890is a reference distance

in the same unit of 119889 the shadow (or large-scale) fadingparameter 119904 is a zero-mean Gaussian random variable withstandard deviation 120590 [10] Nevertheless it can be assumedthat the spatial variations at a local scale are only due tosmall-scale fading [11] For instance for the free-space model119860 = 324+20sdotlog(119891) where119891 is frequency in GHz 119889

0= 1m

and 120574 = 2If the path loss follows (1) then the average power density

in Wm2 can be estimated using the following generalizedformula

119878 (119889 120579 0) =119875 sdot 119866max sdot 119865 (120579 0)

119870 sdot 119889120574 (2)

where 119875 is the power supplied to the antenna in 119882 119866maxis the maximum gain of the antenna 119865(120579 120601) is the relativenumerical gain varying with elevation and azimuth angles119870is a fix value for the specific considered model 120574 is the pathloss exponentThe influence of 119865(120579 120601) for NLOS is studied in[12]

21 The Two-Ray Propagation Model The two-ray modelconsiders that between the EMF source and the receiver thereare just the direct ray and a single specular reflected ray thatdominates the multipath effect The direct ray propagatesthrough free space and the reflected ray is proportional to thedirect electric field intensity by a complex factor Γ (reflectioncoefficient) With this model the nonuniform distributionalong the whole body can be shown mainly for ultrahighfrequencies (UHF) or above

For a fast and conservative estimation of the powerdensity it is common to consider that the reflected ray is in-phase with the direct ray so that the power density can becalculated as

119878 (119889 120579 0) =(1 + |Γ|)

2sdot 119875 sdot 119866max sdot 119865 (120579 0)

4 sdot 120587 sdot 1198892 (3)






119878 (119889 120579 0) =119875 sdot 119866max sdot 119865 (120579 0)

20811988926 (4)














x

x

asymp120573

120573

(a) (b)





2+ (119867 minus ℎ)

2]12 in (2) where


119909 = 119883expmax


120574)]

2

+4 sdot 119902 sdot (119867 minus ℎ)

2

120574


120574)) times 05

(5)






0

1

2

3

4

5

6


Pow

er d

ensit

y (m

Wm

2)












max 75m 120574 = 2



55

60

65

70

75

80

85

90

95

20 200

Path

loss

(dB)





PL = 234 + 266 log (119889) (6)



0= 1m


119878 (119889 120579 0) =119875 sdot 119866max sdot 119865 (120579 0)

189 sdot 119889266 (7)






max 56m 120574 = 266







Tilt (120572) 6∘ 10∘




1205721015840= 98∘

1205721015840= 138

∘

116m 79m


1205721015840= 98∘

1205721015840= 138

∘




1015840= 138





0

500

1000

1500



Pow

er d

ensit

y (120583

Wm

2)


0 50 100 150 200d (m)


minus100

minus80

minus60

minus40

minus20

0

P(R

SRP)

(dBm

)






0 50 100 150 200 250d (m)


P(R

SRP)

(dBm

)

minus100

minus80

minus60

minus40

minus20

0


5 Conclusion






Appendix


119875119877=EIRP119871

=119875 sdot 119866max sdot 119865 (120579 0)

119871 (A1)


where 119871 = 10119871dB10 and 119871


power density is

119878 =119875119877

119860eff=

EIRP119870 sdot 119889120574

(A2)

where 119860eff = 12058224120587


119870 =119860eff sdot 119871

119889120574 (A3)



Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation














119878 (119889 120579 0) =119875 sdot 119866max sdot 119865 (120579 0)

20811988926 (4)














x

x

asymp120573

120573

(a) (b)





2+ (119867 minus ℎ)

2]12 in (2) where


119909 = 119883expmax


120574)]

2

+4 sdot 119902 sdot (119867 minus ℎ)

2

120574


120574)) times 05

(5)






0

1

2

3

4

5

6


Pow

er d

ensit

y (m

Wm

2)












max 75m 120574 = 2



55

60

65

70

75

80

85

90

95

20 200

Path

loss

(dB)





PL = 234 + 266 log (119889) (6)



0= 1m


119878 (119889 120579 0) =119875 sdot 119866max sdot 119865 (120579 0)

189 sdot 119889266 (7)






max 56m 120574 = 266







Tilt (120572) 6∘ 10∘




1205721015840= 98∘

1205721015840= 138

∘

116m 79m


1205721015840= 98∘

1205721015840= 138

∘




1015840= 138





0

500

1000

1500



Pow

er d

ensit

y (120583

Wm

2)


0 50 100 150 200d (m)


minus100

minus80

minus60

minus40

minus20

0

P(R

SRP)

(dBm

)






0 50 100 150 200 250d (m)


P(R

SRP)

(dBm

)

minus100

minus80

minus60

minus40

minus20

0


5 Conclusion






Appendix


119875119877=EIRP119871

=119875 sdot 119866max sdot 119865 (120579 0)

119871 (A1)


where 119871 = 10119871dB10 and 119871


power density is

119878 =119875119877

119860eff=

EIRP119870 sdot 119889120574

(A2)

where 119860eff = 12058224120587


119870 =119860eff sdot 119871

119889120574 (A3)



Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










x

x

asymp120573

120573

(a) (b)





2+ (119867 minus ℎ)

2]12 in (2) where


119909 = 119883expmax


120574)]

2

+4 sdot 119902 sdot (119867 minus ℎ)

2

120574


120574)) times 05

(5)






0

1

2

3

4

5

6


Pow

er d

ensit

y (m

Wm

2)












max 75m 120574 = 2



55

60

65

70

75

80

85

90

95

20 200

Path

loss

(dB)





PL = 234 + 266 log (119889) (6)



0= 1m


119878 (119889 120579 0) =119875 sdot 119866max sdot 119865 (120579 0)

189 sdot 119889266 (7)






max 56m 120574 = 266







Tilt (120572) 6∘ 10∘




1205721015840= 98∘

1205721015840= 138

∘

116m 79m


1205721015840= 98∘

1205721015840= 138

∘




1015840= 138





0

500

1000

1500



Pow

er d

ensit

y (120583

Wm

2)


0 50 100 150 200d (m)


minus100

minus80

minus60

minus40

minus20

0

P(R

SRP)

(dBm

)






0 50 100 150 200 250d (m)


P(R

SRP)

(dBm

)

minus100

minus80

minus60

minus40

minus20

0


5 Conclusion






Appendix


119875119877=EIRP119871

=119875 sdot 119866max sdot 119865 (120579 0)

119871 (A1)


where 119871 = 10119871dB10 and 119871


power density is

119878 =119875119877

119860eff=

EIRP119870 sdot 119889120574

(A2)

where 119860eff = 12058224120587


119870 =119860eff sdot 119871

119889120574 (A3)



Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation















max 75m 120574 = 2



55

60

65

70

75

80

85

90

95

20 200

Path

loss

(dB)





PL = 234 + 266 log (119889) (6)



0= 1m


119878 (119889 120579 0) =119875 sdot 119866max sdot 119865 (120579 0)

189 sdot 119889266 (7)






max 56m 120574 = 266







Tilt (120572) 6∘ 10∘




1205721015840= 98∘

1205721015840= 138

∘

116m 79m


1205721015840= 98∘

1205721015840= 138

∘




1015840= 138





0

500

1000

1500



Pow

er d

ensit

y (120583

Wm

2)


0 50 100 150 200d (m)


minus100

minus80

minus60

minus40

minus20

0

P(R

SRP)

(dBm

)






0 50 100 150 200 250d (m)


P(R

SRP)

(dBm

)

minus100

minus80

minus60

minus40

minus20

0


5 Conclusion






Appendix


119875119877=EIRP119871

=119875 sdot 119866max sdot 119865 (120579 0)

119871 (A1)


where 119871 = 10119871dB10 and 119871


power density is

119878 =119875119877

119860eff=

EIRP119870 sdot 119889120574

(A2)

where 119860eff = 12058224120587


119870 =119860eff sdot 119871

119889120574 (A3)



Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










0

500

1000

1500



Pow

er d

ensit

y (120583

Wm

2)


0 50 100 150 200d (m)


minus100

minus80

minus60

minus40

minus20

0

P(R

SRP)

(dBm

)






0 50 100 150 200 250d (m)


P(R

SRP)

(dBm

)

minus100

minus80

minus60

minus40

minus20

0


5 Conclusion






Appendix


119875119877=EIRP119871

=119875 sdot 119866max sdot 119865 (120579 0)

119871 (A1)


where 119871 = 10119871dB10 and 119871


power density is

119878 =119875119877

119860eff=

EIRP119870 sdot 119889120574

(A2)

where 119860eff = 12058224120587


119870 =119860eff sdot 119871

119889120574 (A3)



Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










where 119871 = 10119871dB10 and 119871


power density is

119878 =119875119877

119860eff=

EIRP119870 sdot 119889120574

(A2)

where 119860eff = 12058224120587


119870 =119860eff sdot 119871

119889120574 (A3)



Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









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