dosimetry: present researches and future challenges · @ 2008 joe wiart recherche &...

recherche & développement

DOSIMETRY:Present researches and future challenges

Joe Wiart & Man Fai Wong

Orange Labs

""Il faut de l'imagination pour se Il faut de l'imagination pour se

reprrepréésenter la rsenter la rééalitalitéé" "

Giuseppe Giuseppe PontiggiaPontiggia

@ 2008 Joe Wiart recherche & développement Groupe France Télécom

Outline

� What is dosimetry

� Why dosimetry is facing the uncertainty

� What are the preliminary investigations


Why performed dosimetric studies

� Understand how the RF energy is deposited in biological

tissues

� Design exposure system applicable for in vivo and in vitro

� Check the compliance of system to limits

� Assess the exposure encountered in operating network


Exposure assessment facing multiple Wireless communication technologies

� A few hundred millions of handset user

� Communicating objects

� Different technologies

� Different frequencies (FM, TETRA,TV, GSM,

UMTS, WIFI, WIMAX, UWB ….)

� Different protocols (TDMA,

CDMA,CSMA/CA,…)

� Variable channel occupancy

Number of users (millions) in France vs years


Large efforts carried out in ANR and RNRT projects

� Past project

� COMOBIO

� ADONIS

� On-going projects

� OP2H

� MULTIPASS

� ANR SAMPER

� Starting projects

� MERODAS


Standards have been developed: The example of Europe

� Mobile :

� Put on the market :

• EN 50360 & 50361: Adopted in 2000 and replace by the IEC 62209-1 adopted

in 2006

� For new usages and higher frequencies: IEC 62209-2

� Base Station

� Put on the market

• EN 50383 & EN 50384 adopted in 2002

� Put into service

• EN50400 & EN 50401 adopted in 2006

� In situ measurement

• EN50492 Adopted in 2008


Large efforts have been done to develop experimental equipments

� Small SAR probes have been developed

� Small E & H probes developed

� Probes for in situ measurement

� Personal dosimeter

Small SAR isotropic probes

Small H field probe

E field probe


Numerical methods have been adapted and improved.

� SAR and temperature calculations are not

anymore a problem.

� Simulations are larger and larger, faster and

faster

• Finite Difference in Time Domain (FDTD) has been

improved (ABC's..)

• Computer Memory increases

• Processors are faster

• Graphic cards used to accelerate the calculations

• New approaches ADI-FDTD, CFDTD…

� Field estimation

� Tools have been developed


Exposure system are well characterized

0 5 10 15 20 25 30 35 400

5

10

15

Skin

SAR Histograms per tissue (100 highest value)

0 5 10 15 20 25 30 35 400

50

100

Skull

0 5 10 15 20 25 30 35 400

5

10

15

Dura

matt

er

0 5 10 15 20 25 30 35 400

10

20

30

Bra

in

W/kg for 1 Watt emitted


Numerical methods have been adapted and improved.� SAR and temperature calculations are not

anymore a problem.

� Simulations are larger and larger, faster and

faster

• Finite Difference in Time Domain (FDTD) has been

improved (ABC's..)

• Computer Memory increases

• Processors are faster

• Graphic cards used to accelerate the calculations

• New approaches ADI-FDTD, CFDTD…

� Field estimation

� Tools have been developed


Numerical methods are quitemature…

recherche & développement


But they are facing representativeness

Ratio between MSAR10g and the MSAR1g in brain tissues

0.30.6Std

1.52.5Median

1.42.5Mean

ChildrenAdultsMSAR10g/MSAR1g in brain

FACING


And complexity

� Complex environment

� Complex, non regular and multiples

sources

� Complex and variable bodies


Facing complexity : models, methods adapted to targetaccuracy� Field prediction / MoM,… PO vs Go + homogeneisation

� Model resolution

s1

s2

s3s4

r1

r2

r3

r4

E

R1s5

r5R2

1mm 2mm


Facing complexity : Hybridapproaches adapted to target accuracy

� Hybrid methods : eg Domain decomposition

� Combining measurement and simulation

� Rat in reverberating chamber


Facing uncertainty

x1

xi

xN

Y1

Yi

YM


Surrogate model?

How determine the key parameters influencing the SAR

X=(Height, Weight, Surface, upper segment, perimeter, BMI…)

SAR=f(X); Is it possible to limit the dimension of X

Are these parameters accessible ?

{Xi} are not independent

How get the joint probability law?

1800MHz


Thanks

Dans la confusion trouver la simplicité

De la discorde faire jaillir l'harmonie

Au milieu de la difficulté se trouve l'opportunité

Albert Einstein,

Trois règles de travail

dosimetry: present researches and future challenges · @ 2008 joe wiart recherche &...

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