eMBB

mIoT / mMTC URLLC

5G – The overall test challenge

from system to device 5G NR T&M aspects

Reiner Stuhlfauth

Technology Manager Wireless

Rohde & Schwarz

Optimizing the present. Designing the future.

eMBB

mMTC

URLLC

T&M

µ-wave

Cybersecurity

EMC + AutomotiveAerospace&

Defence

Broadcast&

Media

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5G testing aspects - outline

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• 5G NR RF measurements

• Over the air – a paradigm change in testing setups

•

• Can we measure in the Near-field?

•

• How to obtain Far-field condition for UEs and basestations?

• 3GPP status on OTA testing

• Outlook – future and additional aspects of OTA testing

• System and field testing of 5G NR

NR Frame Structure@mm-wave – spectrum analysis5G NR critical RF parameters

compared to LTE testing:

- Power flatness over

wide bandwidth (~100MHz)

- Spectrum emission mask

- EVM performance=>

Impact of phase noise

- EVM vs. Subcarrier =>

Impact of DC leakage

- Power vs. Time => shorter

Symbols and wider bandwidth

- Symbol allocation => much

higher flexibility of RF layer

What are we going to test in 5G NR?

=> For sure the usual suspects: power, spectrum, modulation, receiver, etc.

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NR Frame Structure@mm-wave – spectrum analysis5G NR critical RF parameters

compared to LTE testing:

- Power flatness over

wide bandwidth (~100MHz)

- Spectrum emission mask

- EVM performance=>

Impact of phase noise

- EVM vs. Subcarrier =>

Impact of DC leakage

- Power vs. Time => shorter

Symbols and wider bandwidth

- Symbol allocation => much

higher flexibility of RF layer

Analysis of different numerologies and carrier bandwidth parts with different modulation schemes

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You can‘t cheat physics!

ı Significant higher data rates / capacity is only

possible with higher bandwidth

ı Higher bandwidth is only possible at higher

spectrum

ı We do know the challenges of propagation at cm-

/mm-wave spectrum

Example: field measurement @28GHz

𝐶 = 𝐵 ∙ 𝑙𝑜𝑔2 1 +𝑆

𝑁

Bandwidth

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You can‘t cheat physics …… but an engineer will find a solution!ı Active antenna systems with a high number of antenna elements, which can be

individually controlled in phase and amplitude, enable high antenna gains and beam

steering.

Reconfigurable 28GHz All-Silicon ArrayMassive MIMO Antenna@ 3.5GHz

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An engineer solves his problem…… by creating another engineers problem!

ı High number of antenna

elements each connected

to phase shifters and PAs

Limited test interfaces

ı High integration in

particular at cm- and

mm-wave spectrum

No RF connectors

RFIC RFIC

TR

x

FPGA

Digital IQ

Development challenges like

phase shifter tolerances, thermal

effects of the PAs, frequency

drifts between modules, desired

beam patterns, …

Over the air (OTA) measurements

in far field becomes the default

test scenario

OTA measurements require

shielding

Cost / Complexity impact

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Fraunhofer distance. Near field vs. far field

Near-field region =

phase & magnitudeVery near-

field region

Far field=

magnitude

2D2 / λ0.62 D3 / λ

Near field measurements:

• values depend on phase & magnitude

not simple for modulated signals (wide bandwidth,

phase coherent receiver needed)

• multiple samples are needed, i.e. spherical scan

near-field to far-field transformation is

needed (additional time + effort)

=> single probe + rotation concept (accurate positioner

needed) or multi-antenna probe (calibration complexity)

• Smaller chamber sizes

Far field measurements:

• values depend on magnitude only

suitable for modulated signals

• one sample is sufficient, no NF/FF post-processing

• Larger chamber sizes required or hardware FF

transformation like PWC or CATR (higher complexity)

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Measurement dilemma: can we do measurements in near field?

E.g. EVM aspects NF vs. FFMeasuring EVM in near field:

Near field samples are varying in

phase + amplitude => certain

unaccuracy is the result

Measuring EVM in far field:

Pathloss will reduce the received

signal to noise ratio

DUT has to be measured at max

and min power

Sensitivity level of test instrument

has to be considered

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Measurement resultsActive antenna array @ 28GHzı 5G NR signal (100 MHz, 64QAM data, fully

allocated) with crest factor of 11.5dB

ı Generated with SMW200A and

received/analyzed with FSW43

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EVM

measurement

in NF

possible?

EVM <0,7% when

sufficient SNR.

Problem at higher

power due to

overdriven PA

What is the Far-field distance? 2 additional methods

DU

T=

10

cm

Dant=4cm28GHz UE Subarray

(HPBW=15°)

Criteria Far-field Distance

2λ/HPBW2 0.30 meters

28GHz Entire UE

2D2/λ 1.86 meters

HPBW (radians)

Half-power beam

width

𝑅𝐹𝐹 =2𝐷2

𝜆𝑜𝑟

2𝜆

𝐻𝑃𝐵𝑊2

3dB power

difference

θ

𝑅𝑓𝑓𝐷 = 𝜆𝜋𝐷

𝜆

0.8633

0.1673𝜋𝐷

𝜆

0.8633

+ 0.1632

Consideration only in peak beam direction allows to re-consider FF distances: APEMC 2018 [Derat, « 5G

antenna characterization in the far-field – How close can far-field be? »] - based on spherical wave expansion

15 cm DUT @ 24 GHz

FHD = 3.6 m

RffD = 1.14 m

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Far-field in Near-field Systems: Hardware Fourier Transforms

Complex near-field

wave generated

Fresnel Lens (Fourier Optics) Reflector: Compact Antenna Test Range Array: Plane Wave Convertor

Amplitude PhasePlane wave far-

field received

DUT

𝑓𝑥,𝑦 = 𝐴ඵ𝐸𝑥,𝑦𝑒+𝑗𝐤∙𝐫 𝑑𝑥𝑑𝑦

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How to achieve far-field conditions? Basestation – plane wave idea

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Based on principle of beamforming:

Antenna array with phase shifters. Goal

is not beamforming, but plane wave.

Frequency restricted but allows modulated

wideband signals analysis

R&S®PWC200: Gain & Pattern Results

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Certified Lab Results

(Spain)

PWC200 Results

1.5m from DUT

Single Antenna

1.5m from DUT

EVM = 0.41%

Roughly the internal EVM of measurement

instruments

LTE signal: 5CC @20MHz

5G NR @100MHz

3GPP statusUE testing > 24GHz (note that below 6GHz conducted testing is still used)ı Background information in 3GPP TR 38.810

ı 3GPP distinguishes between RF, RRM and demodulation and CSI testing and testing

methodologies

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UE RF testing:• Permitted test

methods are direct far

field (DFF) testing and

indirect far field (IFF),

i.e. CATR

• EIRP, TRP, EIS, EVM,

spurious emissions

and blocking metrics

can be tested

UE RRM testing

• Only baseline

measurement setup

defined so far

UE demodulation and

CSI testing

• Only baseline

measurement setup

defined so far

Work in progress!

Stable already!

3GPP StatusUE testing – RF testing

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LinkAntennaforbeamsteering

MeasurementAntennaforcentreandoffcentreofbeammeasurements

Link/MeasurementAntennaforbeamsteeringandcentreofbeammeasurements

PM/SGPositioner

controller

PC

1

2

3

Range antenna reflectorDUT

Feed antenna

z

xy

4Direct far field:

Measurement

&

Link antenna

(combined

Or separated)

Indirect far field: e.g. CATR

What is the Quiet zone ?

+D/2

-D/2

R

R

d

Point Source

(Measurement Antenna)

Quie

t Z

one

(D)

φ(R)

φ(R+d)

𝑅𝑚𝑖𝑛 =𝜋𝐷2

4𝜆Δ𝜑𝑚𝑎𝑥=𝑁𝐷2

𝜆

Quiet Zone Phase Deviation vs. Measurement Error

Rmin(N)Phase Deviation

𝐷2/𝜆 45 degrees

2𝐷2/𝜆 22.5 degrees

4𝐷2/𝜆 11.2 degrees

8𝐷2/𝜆 5.6 degrees

𝑁 = ∞

-25 dB

-30 dB

-20 dB

𝑁 = 2

𝑁 = 4

High Gain Antenna Pattern

Note: Near field regions don‘t have „quiet zones“

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IFF solution for BlackboxDFF solution for Whitebox

Elevation

arm

0-168°

Azimuth

+/- 180°

Azimuth

& Theta

+/- 180°

Both systems fit

in ATS form factor

Direct far field: typically smaller QZ Indirect far field: typically larger QZ

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3GPP StatusUE testing – RRM testingı “The exact list of RRM tests for UE can only be

determined once the core requirements are settled”

ı The baseline measurement setup for f > 6 GHz is

capable of establishing an OTA link between the DUT

and a number of emulated gNB sources

ı Up to 2 NR transmission reception points TRxPs are emulated

ı N dual-polarized antennas transmitting the signals from the emulated gNB sources to the DUT.

ı N ≥ NMAX_AoAs, where NMAX_AoAs is the maximum number of simultaneously active (emulating signal)

angles of arrival AoAs. For the scope of Rel-15 testing, it is assumed that NMAX_AoAs = [2].

ı In case of multiple DL transmission antenna ports are required for RRM testing, the transmission

scheme is polarization diversity.

ı Fading propagation conditions between the DUT and the emulated gNB sources are modelled as

Tapped Delay Line (TDL).

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OTA testing with temperature control

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S21 parameter influenced by temperature changes

RRM case study : OTA 3D Measurements

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The receiver antenna characteristics

determines UE RSRP measurement.

UE RSRQ measurement does not depend on the

receiver antenna characteristics

Serving cell emulation

Neighbour (interfering)

Cell emulation

RF Scanner TSMx / ROMES for mm-wave testing

Receive

antenna

IF: 3 GHz

R&S®ROMES Drive Test Software

R&S®TSMA6 Autonomes Mobile

Network Scanner and

R&S®ROMES Drive Test Software

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R&S®TSME30DC

DownconverterR&S®TSME6 Ultra Compact

Drive Test Scanner

5G NR scanning of

SSB

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What can be measured? Trial @5G NR - 28GHz channels

“If you want to go fast, go alone. If you want to go far, go together!”

African proverb

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