Exposure of the general public due to GSM and UMTS base station transmitters

Dr. Christian Bornkessel,Markus Schubert IMST GmbHCarl-Friedrich-Gauß-Str. 2D–47475 Kamp-Lintfort

Prof. Dr. Matthias WuschekEM Institut GmbHCarlstraße 5D-93049 Regensburg

Workshop Dosimetry, 25.-26.07.2006

Project Overview

• Literature study on existing projects

• Characterisation of time and space field variations

• Development of measurement and calculation methods

- Focus: Check of exposure limits- In addition: Time and space averaged exposures

• Measurements in different scenarios

• Analysis of field distribution and exposure parameters

70

75

80

85

90

95

100

0 20 40 60 80 100 120 140

place [cm]

elec

tric

fiel

d st

reng

th [d

BµV

/m]

GSM 900

UMTS

Small scale field variation in space

• Small scale variations (fast fading) especially at indoor scenariosdue to multipath propagation

• Variations of 10 dB and more

Simulation: GSM 900Measurement: GSM 900 and UMTS

Small and large scale variations in time

time

1

1,5

2

2,5

3

3,5

4

12:00 16:00 20:00 0:00 4:00 8:00 12:00

elec

tric

fiel

d st

reng

th [V

/m]

day

Tu We Th Fr Sa Su Mo Tu

2.0

1.8

1.6

1.4

1.2

1.0

elec

tric

fiel

d st

reng

th [V

/m]

Measurement: GSM 24 hours Measurement: GSM 7 days

• Small and large scale variations due to traffic load (power control)

German Exposure Ordinance (26. BImSchV) demands ...

• Exposure limits are given as- RMS value of- electric and magnetic field strength

• Measurements have to be performed at the highest operational state of the station; otherwise they have to be extrapolatedaccordingly

• Measurements have to be performed at the place with the highest exposure

• Post processing of measurement results on basis of the maximal measured fields strengths or power densities at the measurement place

To account for the space variations

• Measurements on a fix point(e.g. antenna on a tripod) does not make sense

• Maximisation of exposure in a space volume:

- sweeping method,- rotation method,- raster method

• Further post processing withthe maximal measured value

To account for the time variations: GSM

• Frequency selectiveequipment

• Measure time constant signalling channels (BCCH)

• Extrapolate their exposure to maximal channel number

• Ignore TCH exposure

• Summarise exposures of all sectors

1820 1830 1840 1850

frequency [MHz]

50

60

70

80

90

100

110

120

BC

CH

sec

tor

1

x

x

x4

x4

elec

tric

fiel

d st

reng

th [d

BµV

/m]

x4

x

BC

CH

sec

tor

3

BC

CH

sec

tor

2

TC

HT

CH

TC

H

� Frequency hopping is automatically accounted for

Frequency selective measurements for UMTS?

2110 2120 2130 2140 2150 2160 2170

Frequenz [MHz]

0,0001

0,001

0,01

0,1

1

Ele

ktri

sch

e F

eld

stär

ke [

V/m

]

Vod

afon

e

E-P

lus

O2

T-M

obile • Operators can be separated

by different frequency

• Different stations cannot beseparated (SFN!)

• present traffic load is not known

�Extrapolation to maximal operational state only possible under assumption "no traffic load"; this overestimates real exposure

frequency [MHz]

elec

tric

fiel

d st

reng

th [V

/m]

Code selective measurement for UMTS!

• Different stations/sectors are separated by "scrambling codes"

• Physical channels are separated by "spreading codes"

• P-CPICH is a permanent signalling channel with spreading code 0

• P-CPICH transmits with constant power and can be used for extrapolation

Scrambling code 105

Scrambling code 375

Scrambling code 22 Scr. Code Frequency Field strength Power densityMHz V/m µW/cm²

22 2112.8 0.145 5.58E-03105 2112.8 0.0106 2.98E-05375 2112.8 0.023 1.40E-04175 2167.2 0.047 5.86E-04

Sum (RMS): 0.1545 V/m

Max. Value: 0.1450 V/m

Detailed investigations of several code selective d evices

Rohde & SchwarzTSMU

Rohde & SchwarzFSP/ESPI with

code-selective option

Narda SRM-3000

� Investigations on measurement rate, accuracy, dynamic, linearity, reproducibility, uncertainty, ...

Analyser settings for spectral measurements

100 msAuto (Peak)100 ms (RMS)

Sweep time

RMSPeak or RMSDetector

10 MHz≥ 200 kHzVBW

5 MHz*200 kHzRBW

UMTSGSMSetting

� Wrong settings can lead to wrong results (several d B to several 10 dB)

*: Alternatives (bandwidth correction, channel power measurement) possible, but lead to overestimations at NLOS conditions

Influence of personnel on measurement antenna

• Tests in anechoic chamber (defined environment)• Parameters: ground plane lining, frequency, antenna type,

distance of the measurement personnel

measurement antenna

Results: Example 945 MHz (GSM 900)

0 0,5 1 1,5 2 2,5 3

Abstand zur Empfangsantenne [m]

-10

-5

0

5

10

rela

tive

Ab

wei

chu

ng

[d

B]

Legendelogper Pol Hbikon Pol Hlogper Pol Vbikon Pol V

0 0,5 1 1,5 2 2,5 3

Abstand zur Empfangsantenne [m]

-2

-1,5

-1

-0,5

0

0,5

1

1,5

2

rela

tive

Ab

wei

chu

ng

[d

B]

Legendelogper Pol Hbikon Pol Hlogper Pol Vbikon Pol V

w/o ground plane absorbers with ground plane absorbers

� Partially extreme influence by measurement personne l onlow directive antennas

� AT UMTS frequencies: up to 3 dB difference

distance to receive antenna [m]distance to receive antenna [m]

rela

tive

diffe

renc

e [d

B]

rela

tive

diffe

renc

e [d

B]

Measurements in 11 scenarios1. Low mounted station in a rural environment

2. High mounted station in a rural environment (mast installation)

3. Base station in a commercial area

4. Low mounted station in an urban environment

5. High mounted station in an urban environment

6. Ultra high site

7. Station for indoor coverage

8. Station for coverage of a football stadium

9. Station for coverage of an exhibition hall

10. Station for coverage of a pico cell

11. Station on a roof and exposure measurements in the building below

� UMTS and GSM base stations are at the same site!

Results: GSM/UMTS Min/Max

0,01

0,10

1,00

10,00

100,00

elec

tric

fiel

d st

reng

th in

% o

f lim

it

1 2 3 4 5 6 7 8 9 10 11

GSM

UMTS

scenario no.

8.4 % limit5.1 V/m69.3 mW/m²

0.01 % limit0.01 V/m0.1 µW/m²

12.8 % limit5.4 V/m78.3 mW/m²

0.01 % limit0.004 V/m0.03 µW/m²

Discussion

0,01

0,10

1,00

10,00

100,00

elec

tric

fiel

d st

reng

th in

% o

f lim

it

1 2 3 4 5 6 7 8 9 10 11

GSM

UMTS

low mounted antennas (micro cell / indoor scenarios)

low mounted antennas

high mounted antennas

Distribution of results

64,4

18,4

4,33,1 3,1

1,8 2,51,2 1,2

0,0 0,0

34,9

18,3 17,5

8,77,1

8,7

1,6 1,60,0 0,8 0,8

0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

0 - 1 1 - 2 2 - 3 3 - 4 4 - 5 5 - 6 6 - 7 7 - 8 8 - 9 9 - 10 > 10

field strength in % of limit

rela

tiv n

umbe

r of

poi

nts

in %

UMTS

GSM

median UMTS: 0.72 % of field strength limitmedian GSM: 1.75 % of field strength limit

Distance as a main factor for exposure?

0,01

0,1

1

10

1 10 100 1000 10000

distance to base station [m]

elec

tric

fiel

d st

reng

th [%

of l

imit]

Indoor

Outdoor

Answer: Outdoor no (up to approx. 200 m)Indoor yes

Explanation

-35-35

-30

-30

-25

-25

-20

-20

-15

-15

-10

-10

-5

-5-40

-40

180°

135°

0°

90°270°

45°

-35-35

-30

-30

-25

-25

-20

-20

-15

-15

-10

-10

-5

-5-40

-40

180°

135°

0°

90°270°

45°

1 10 100 1000 10000

Abstand d [m]

1E-006

1E-005

0,0001

0,001

0,01

0,1

1

10

Lei

stu

ng

sflu

ssd

ich

te [

W/m

2]

distance [m]

pow

er d

ensi

ty [W

/m²]

Vertical angle as a main factor for exposure?

Answer: Vertical angle (orientation to main lobe)is well suited!!

0

0,5

1

1,5

2

2,5

-6 - 0° 0 - 5° 5 - 10° 10 - 15° 15 - 20° 20 - 30° > 30°

vertical angle [degree]

aver

age

elec

tric

fiel

d st

reng

th [%

of l

imit]

111 m

704 m 249 m

99 m

136 m

49 m

50 m

Sight conditions as a main factor for exposure?

Answer: Yes, but reflections have to betaken into account!

0,01

0,1

1

10

1 10 100 1000 10000

distance [m]

elec

tric

fiel

d st

reng

th [%

of l

imit]

direct sightno or limited sight

Relation of G

SM

/ UM

TS

exposure(1)

0 2 4 6 8 10 12 14

1.11.21.31.41.51.61.71.81.9

1.101.111.121.131.141.151.161.171.181.191.201.211.22

2.12.22.32.42.52.62.72.82.9

2.102.112.12

3.13.23.33.43.53.63.73.83.9

3.103.113.223.133.143.153.163.17

4.14.24.34.44.54.64.74.8

measurem

ent point no.

electric field strength [% of limit]

GS

M

UM

TS

Relation of G

SM

/ UM

TS

exposure (2)

0 2 4 6 8 10 12 14

5.15.25.35.45.55.65.75.85.9

5.105.115.125.135.145.155.165.175.185.195.205.215.225.235.245.255.265.27

8.18.28.38.4

9.19.29.39.49.59.6

10.110.210.310.410.510.610.7

11.111.211.311.411.511.611.711.811.9

11.1011.1111.1211.1311.1411.1511.1611.1711.1811.1911.2011.2111.2211.23

measurem

ent point no.

electric field strength [% of limit]

GS

M

UM

TS

�G

SM

> UM

TS

at 85 % of all points (com

pared to limit

)

Broader main lobe of GSM 900 compared to UMTS

GSM900:• Mounting height 30 m• Antenna K 739 681• Downtilt 3°• Transmit power 20 W

UMTS:• Mounting height 30 m• Antenna K 742 212• Downtilt 3°• Transmit power 20 W

Simulation with FieldView, EM-Institut GmbH

Simulated distance profile

0

0,5

1

1,5

2

2,5

3

3,5

0 100 200 300 400 500 600 700 800 900 1000

distance [m]

elec

tric

fiel

d st

reng

th [%

of l

imit]

GSM 900

GSM 1800

UMTS

triple band antenna K 742265, 20 m height, 20 W per system, downtilt 0°each

Calculation methods: Commercial software

Exposure (GSM+UMTS)EM-InstituteFree spaceFieldView

Exposure (GSM+UMTS)RemcomRay-optical with phaseWireless Insite

Exposure (UMTS)AWE - communicationsRay-optical and empiricalWinprop

Exposure (GSM+UMTS)TESRay-OpticalQuickplan

Installation vicinityEM Software & SystemsHybrid (e.g. MoM, UTD)Feko

Installation vicinity + small scaleIMST FDTDEmpire

Exposure (GSM)AntennessaRay-OpticalEMF-Visual

Exposure (GSM+UMTS)FGEURay-Optical without phaseEFC-400

ApplicationManufactureMethodSoftware

Central question:

Suitability of calculation methods to determine the public exposure due to electromagnetic fields around (outside the regulato ry safety distance) cellular GSM and UMTS base station transceivers

0

45

90

135

180

225

270

315

0,01

0,1

0,1

1

1

-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90-35

-30

-25

-20

-15

-10

-5

0

5

10

15

20

Antenna pattern

-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90-35

-30

-25

-20

-15

-10

-5

0

5

10

15

20D

irect

ivity

[dB

i]

Dire

ctiv

ity [d

Bi]

1. Dependency on frequency 2. Dependency on electr. downtilt

Angle [degrees] Angle [degrees]

3. Dependency on installation vicinity

Antenna pattern: Synthesis

0

45

90

135

180

225

270

315

-50

-40

-40

-30

-30

-20

-20

-10

-10-50-50

Influence of the terrain profile

BTS

without terrain data with terrain data

Simulation result with EFC-400:

Terrain profile

BTSBTS

Building informationBlack-White picture from land registerSatellite picture

Import in Winprop and Quickplan

� Cooperation with land surveying office NRW

Building information: „Vectorisation“

Vectorising the black building shapes Import in EFC-400

Generate 3rd dimension

Import in Wireless Insite

„Corel Draw“

„Autocad“

EFC-400

EFC-400 (FGEU)

• Ray-optical without phase information

• Consideration of

• Terrain data: yes

• Building data: yes

• Synthesised pattern: yes

• Indoor and outdoor configurations

• Import of a huge number of buildings in vector format possible

• Only rectangular buildings

• 3D plot may be optimised

EMF-VisualEMF Visual (Antennessa)

• Ray-optical with phase information

• Consideration of

• Terrain data: no

• Building data: yes

• Synthesised pattern: no

• Indoor and outdoor configurations

• User-friendly method to generate buildings (e.g. on the basis of satellite pictures)

• Buildings only as decoratives, including requires further steps (former version);results in large computation time

• Input data not geo-referenced

FieldViewFieldView (EM-Institute)

• Free-space

• Consideration of

• Terrain data: no

• Building data: no

• Synthesised pattern: yes

• Calculations in every vertical and horizontal plane is possible

• Additional factor on the transmitted power possible

• Propagation mechanisms other than free space not taken into account

Quickplan

Quickplan (Tes)

• Ray-optical with phase information

• Consideration of• Terrain data: yes

• Building data: yes (automatic generation on the basis of black shapes of the buildings possible)

• Synthesised pattern: yes

• Different calculation models

• Surface (left top): dominant path

• Testpoint (left bottom): „all“ paths

• No indoor configurations

• Simple calculations cumbersome(everything must be geo-referenced!)

WinpropWinprop (AWE-Communications)

• Ray-optical with phase information and empirical

• Consideration of• Terrain data: yes• Building data: yes (automatic

generation on the basis of black outlines of the buildings possible)

• Synthesised pattern: yes

• Indoor and outdoor configurations

• Includes a pre processing step to reduce calculation time

• Only horizontal planes possible

• Possibility of change in calculation parameters requires extended user knowledge

Wireless InsiteWireless Insite (Remcom)• Ray-optical with phase information

• Consideration of• Terrain data: yes

• Building data: yes

• Synthesised pattern: yes

• Indoor and outdoor configurations

• Import of a huge number of buildings in vector format possible

• Includes a database of different materials

• Not suited for large area computations (computation time!)

• Problems in including msi-files

-10

-5

0

5

10

15

20

Results: Line of sight situations (GSM)

Measurementuncertainty

diffe

renc

e ca

lcul

atio

n –

mea

sure

men

t [dB

]

scenario / software1 2 3 4 5 6 7

1 2 3 4 5 6 7 8 9 10 11-10

0

10

20

30

40

50

60

70

Results: Non line of sight situations (UMTS)

Measurementuncertainty

below antenna

diffe

renc

e ca

lcul

atio

n –

mea

sure

men

t [dB

]

scenario / software

Outlook: Application of results

Project: Investigation of sleep quality in persons living near a mobile base station – Experimental study on the evaluation of possible psychological and physiological effects under residential conditions(Management: Charite – Universitätsmedizin Berlin)

Objective: - study of diverse sleep parameters in groups near BTS- double blind study- artificial mobile phone base station signal- measurement of exposure: artificial base station,other base stations, other RF exposure

- 60 persons x 6 base station sites