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R&S Thirty-Five: EMF measurement aspects in 5G



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hello and welcome my name is Hannah

Shuford I am a technology manager

Wireless of Holden Schwarz and in

today's

short session I'd like to touch on a few

aspects of EMF electromagnetic fields

with regards to 5g so why do we need to

measure EMF electromagnetic field is to

measure and verify the human exposure

the electromagnetic fields and

especially to verify standards to verify

sites and to make sure that we do not

trespass limits to get a certain general

acceptance so when we talk about EMF in

details we see a certain influence on

the human yeah and this influence of the

EMF which leads nto regulatory issues

this influence is triggered and set by

certain parameters like the frequency

the power density whether there's a

modulation on the signal and how much or

how long is the exposure time at all

that means the challenges in EMF we have

two simple physics that is fact but we

have world wide and even nation wide

various standards and various procedures

how to measure and out how to look into

the EMF part so I just like to show one

single kind of guideline for EMF

measurement exposure there are ten

thousands of pages of documents

nationwide international etc etc so this

could lead for several weeks of webinars

by the way so I only would like to touch

down on here on the ICN IRP which is the

International Commission of non ionizing

radiation patterns yeah and protections

and they are writing a lot of standards

and documents and proposed procedures

how to perform measurements on EMF and

also what are limits and what are

limiting factors for example we see one

craft issued by the ICN I appear which

is setting certain thresholds for IMF an

EMF exposure what is important for us in

the wireless technology world it's like

here the blue circle you see the zone in

the range of let's say 100 megahertz to

sub 6 gigahertz to 6 Keegan's range and

also here you see different curves which

are defined by this

exposuretime whether this is only a few

seconds exposure or whether this is a

24/7 so general exposure and we have

different kind of limitations for

example we talked about the SAR the

specific absorption ratio you see here

this photo of an artificial head filled

with non electric material and then we

measured the radiation the power

radiated into this certain artificial

net in to measure the EMF exposure

specific absorption ratio in the table

below we have a general limit at rest

hold that we should not trespass in any

circumstances at all so this is let's

say the redline and whatever happens you

should never trespass this limit for any

kind of health issue then we see tables

like that where we have the limits for

EMF depending on the exposure time

whether this is only a single exposure

to occupational or whether this is an

exposure that is 24 hours seven days a

week so public one also important to see

when we talk about EMF measurements

depending on the frequency range for

some in the very low frequency range so

here the standard says less than ten

megahertz we have to measure the

electric field and the magnetic field in

our typical frequency ranges used for

wireless standards so the the hundred

megahertz to six gigahertz for example

we measure only the electric field

according to the standards and

simplified saying what we measure is not

the field we measure power so we have an

antenna which has a known

characteristics we know the antenna

factor okay and we measure the power the

received power and this power is then

converted you see the formulas below

this power is then converted into the

electric field strengths generally

speaking and is an important message we

have two different ways how to measure

the EMF we talk about the frequency

selective measurement and we talk about

a code selective measurement so what's

the difference in the frequency

selective measurement I don't care about

the signal content we have respect from

and Alice

you see T on the left side and we do a

power scan over to certain bandwidth

that we would like to measure and we

detect all signals so every signal that

is his visible within this frequency

band contributes to the overall exposure

the other part is the code selective so

in the code selective measurement we

have a specific signal typically a

reference signal that we know the

structure and then we measure the power

explicitly on this specific code signal

for example the our SRP or for example

an SSP Block in five G from the standard

we have different ways how to measure so

different kind of setups how to perform

EMF measurements I would just like to

show a few examples so first example I

touched already this is this very near

field for the reactive near field SAR so

typically measured in a lab in a

shielded chamber with this artificial

hat with non electric leak hits inside

and then we have to do a lot of

difficult mathematical calculations to

emulate the free space resistance yeah

the typical EMF measurements which is

done on a fast show is this fast scan so

typical with a handheld equipment like

here at the fph a spectrum analyzer with

a handheld isotropic antenna and this

gives you a single snapshot the EMF

exposure at this moment of time at this

position where you currently perform the

measurements this is mainly done for

verifying aside very quickly to get the

general impression how the EMF exposure

looks like a more enhanced level of EMF

exposure is the transmitter site

verification so that means I have to

prepare

I need the strategy I know somehow how

my transmitter looks like yeah so we

know for example about the technology

the antennas where the transmitter is

located what is the exposure time what

is the direction of non-tender for

example and then we build a strategy

where we want to measure how long do we

measure what test equipment is used to

measure etc so just a few examples one

example known already from the legacy

generations like already gsm 3g 4g where

we have the sector wise antenna that

looks into a certain direction so here

it is obvious that i position myself

with the test equipment into that kind

of main direction of the transmitting

antenna to emulate some kind of

worst-case condition furthermore some

standards require multiple measurements

so like a multi-point transmitter

verifications here just two examples

either you do this handheld antenna

steering with your hand you move in

certain ways the antennas and you do a

peak search scan for the power level or

the other method is that you measure at

different altitude heads or another kind

of antenna verification is a kind of

full sight analysis typically performed

by regulators they have to look into

different radio technologies they have

to look into different standards they

have to measure the antenna side at

different positions surrounding the

antenna side and doing some kind of

averaging and integration and last but

not least also here one example we also

have permanent EMF exposure survey like

a monitoring of the EMF in a 24/7 period

so 24 hours seven days a week you

permanently integrate and measure the

EMF and this is typically done by let's

say government agencies regulators who

are monitoring EMF exposure on a certain

side so when we come closer into some

five key aspects the first simple

question means we talk about EMF

exposure but what do we measure given a

simple example I assume I have here a

multi-site no multi-site means there are

several network operators sharing this

side so here the rooftop of a building

and we have installations of multiple

radio technologies there is for example

gsm antenna a 3G UMTS LTE and five chip

so now the question will be what do we

need to measure typicality answer is I

need to measure the EMF on radio

technology a from operator a

need to measure the EMF from radio

technology be from operator B and so on

and so on so that means we need to

identify the EMF from one single

technology from one specific operator

now let's have a look into 5g from the

technology part why is 5g challenging in

terms of EMF exposure first five-cheese

offering beamforming that means we have

under active antennas looking into

certain directions later on mode on this

second and this is a big challenge in

five-team we do not have anymore

1/2 of an signal that is spread over the

entire channel bandwidth so the only

signal that we can use as an always-on

signal in 5g is our SSB the

synchronization block that you know so

this 240 subcarrier bandwidth and this

bandwidth is somehow narrow compared to

the entire channel bandwidth in 5g

unfortunately the traffic in the

resource blocks

besides the SSB depends on the traffic

situation so we are packet-switched so I

cannot do a simple linear extrapolation

from the SSP bandwidth into the entire

channel boundaries of 5g and so we have

to take some assumptions and some

considerations for that another aspect

is the beam forming in 5g so typically

like shown here with the different

colors in my picture the SSBs

so the synchronization blocks are mapped

on different beams sent in different

directions but this is only for the SSB

and now what about the traffic maybe the

traffic uses the same beam as the SS

p.m. or maybe the traffic uses an

alternative and I'll turn it Bheema get

a blue color to dark blue color beam so

then we need to measure a signal but

unfortunately there are Fon signal

contained in the traffic channel that I

use equipment specific so they are

flexibly flexibly configurable so that

means from a test scenario we don't know

how they look like and where they are so

we cannot you

the code selective measurement we have

to do some extrapolation under some

theoretical discussions I will explain

later on a few scenarios that I learned

also I think this is easy in 5g we have

a TDD configuration in Farsi so that's

uplink and downlink in the same timeline

yeah so downlink slots and uplink slots

so that means for EMF exposure I have to

perform a gated measurement to only

trigger into the down a direction for

example and 5g is as many of you know in

the first deployment using a multi-link

that means NSA mode LTE in combination

with 5g so then maybe talk to the

regulator we may need to measure the EMF

on both technologies and combine the

value so that means I need to be able to

measure the EMF exposure from LTE and

combine it with the EMF exposure on 5g

so now what are possible requirements I

learned from certain regulators

worldwide for example some regulators

they say take it simple in Farsi we only

want to verify the general exposure that

means we do a spectral scan in a certain

bandwidth and we measure the EMF is

power within this bandwidth so every

signal that contributes this could be

the serving cell the neighbor cells

another operator everything that is

visible with his disband contributes to

the EMF yeah on only let's say we should

not trespass a limit other regulators

they propose the following because they

know that 5g traffic is fluctuating its

packet-switched so therefore they would

like to assume a kind of full loaded

cell but we cannot force the base

station to sell into a kind of test mode

so then they propose a time averaging

for example you see here the ICN RP

organisation days suggest a six-minute

averaging time or even I Triple E

another organization for example they

propose in some papers an averaging time

of 30 minutes yeah

another example I learned from some

regulators they try to emulate a kind of

worst-case condition so with real

measurement

they scan the SSB the synchronization

block huh but this is what they measure

on the peaks or like here in my figure

in the slide you see they measure the

SSB on the green color so on one beam

this is the strongest beam detected at

this measurement position but then we

know that we have to extrapolate into

the white channel bandwidth and

therefore they proposed here in this

formula you see here this parameter

alpha and alpha is a kind of correlation

factor a theoretical value that takes

into account the total antenna gain so

what I know from the datasheet versus

the antenna gain of the SSB so in this

case they extrapolate into a verse case

conditional on another procedure they

suggest a kind of five-step proposal to

do a spectral EMF measurement in five

steps so like do a quick scan on the

overall spectrum to locate the SSB burst

yeah based on resolution boundary

settings then we obtain a kind of

histogram this is the propagation of the

traffic how the traffic where propagate

and behaves and optionally at the end we

can do some kind of post-processing that

means a kind of adaptation and

correction of the measured values by

some theoretical calculated correction

factors now a more complex procedure for

EMF fix measurement is what I learned

from a regulator and this regulator for

example they try to emulate averse case

condition in 5g so what we see on the

left and up this formula it's the e so

the electric field and here we have to

measure the maximum the maximum is con

is obtained by measuring at different

positions around the base station side

for example by measuring all the SSB

signals that are visible and integrate

them here the Samsung and integrate them

all together and this measurement result

Yi is now multiplied with the parameter

car decay and this K

an extrapolation factor that is then

further divided into different

adaptation factors for example there is

an extrapolation factor taking into

account the permitted power versus the

beam configuration we have an

extrapolation factor of the antenna

itself and we have an extrapolation

factor taking into the counter T DT and

F DT so the uplink downlink

configuration and also the options that

we may have a beam that is fluctuating

so some more details on this procedure

for example is first the requirement is

to measure all the SS PS that are

visible at one single measurement site

so here we see the sum so our test

equipment needs to integrate so to

measure the SSP

in this is all at the same time and then

integrate all the SS B's powers to one

single value together and also to do a

kind of peak search analysis to detect

the strongest EMF here a second is the

correlation factor up that takes into

account a certain beam forming behavior

so what is shown in that slide is the

blue color the traffic channel beam may

be points into another direction as the

SSP beam and also what is possible in

theory that the antenna gain of the

traffic channel beam is a different gain

compared to the SSP gains and this is

then taken into account with this

correction factor when we take into the

account the worst case or the datasheet

maximum power which is this value P I

permitted and this is what's is set in

relation to the power measured on the

SSB and even more difficult sorry this

lightens lots of formulas is an antenna

correction factor that takes into

account the different antenna radiation

pattern of the SSB pattern versus the

traffic or general antenna radiation

pattern for example you see here the

direction one here the SSP is at a

maximum of the antenna pattern and also

the traffic channels also measured at

simoom so that means we don't have to

correct something so antenna correction

factor is set to one if you take a

closer look for exam in Direction three

which is on the right and down in

Direction three you see that the traffic

that general antenna radiation pattern

has some higher gain compared to the SSP

gain so the SSP is attenuated and

therefore we need to correct because we

want to emulate a worst-case condition

and this leads then into an antenna

correction factor which is bigger than

one or even another position its

direction for that means I perform my

measurement at the wrong position

yeah so I'm looking into a side lobe or

into the back yard of the antenna and

not into the main directions so my

measurement results are not plausible

and realistic anymore and this will did

then be corrected in this case I have to

substitute my measured results and take

a complete different antenna correction

factors on that yeah so you see there is

no single solutions for EMF measurement

and also for word and words now we need

to provide different solutions how we

can do test and measurement for EMF what

are our solutions the solutions we are

providing is using our test equipment

and networks can at the TSM e so horn

and Schwarz clearly positions itself and

we propose for EMF in 5g the code

selective so our suggestion is to

measure the SSB the synchronization

clock as the reference signal to measure

the power and therefore we have a

network scanner the TSM II that is used

normally in try of tests to perform

network measurements coverage

measurements to control the scanner we

have developed a functions on our

quality POC software which is an

application on the smartphone and this

application controls the scanner

nevertheless I can also use the Houmas

software together with the scanner or we

also have a frequency selective

measurement possible so we have our

spectrum analyzer portfolio and here for

example I can use the handheld with an

isotropic antenna to perform the

spectrum frequency selective

measurements if the regulator says so

here more details

this code selective 5g EMF we're using

the TSM ear which is the fastest scanner

and the highest accurate scanner that we

can get yeah and this scanner is able to

measure multiple SSPs in Farsi on

multiple frequencies in a very fast time

to control this Canon to have an easy

graphical user interface we use the

quali park software and just as an

example here you can see the EMF valued

already an easily displayed in the

software in the screen of your

smartphone we combine the scanner with

antennas for example here two antennas

like the top one is an omnidirectional

antenna with certain known

characteristic or we can also use a kind

of directive antenna you see here on the

lower part of the slide a kind of

directive antenna that allows us to

connect these antennas to the scanner

here's a meal and to perform 5g EMF

measurements another option is of course

to use the TSM iam with the software

home s gomez is developed for drive

testing it's a very powerful software

which gives me a lot of information and

of course we include the EMF values also

measured in the Hohmann software now but

the point is if you only need to measure

EMF and you are not interested in like

benchmarking in network quality analysis

in interference measurement on your real

network in addition to that if you only

need to measure EMF measurements then we

can do the easy way and trust use a

smartphone yeah instead of a PC which

has more processing power so hormuz is

possible for those customers who use

already Roma's and last but not least we

can also offer the spectrum the

frequency selective EMF exposure and

this is done shown here is with a few

photos for example is our today handheld

spectrum analyzer fs.h or spectrum wider

fph they have a bandwidth up to 20

megahertz or we will offer the font and

remote radio at the nrq which has a

bandwidth of 100 megahertz combined with

four it

isotropic antenna and this gives you the

full 500 megahertz channel bandwidth in

fr one to perform EMF exposure yeah so

that's about some aspects in five team

EMF measurements

you know details matter it's worse way

to get it wired but we hope that we have

a wide solutions for five gmf

measurements thank you for your time and

stay tuned

good bye