Atsushi YamamotoPanasonic Corporation, Japan

Panasonic Mobile Communications Corporation, JapanNTT DOCOMO, INC., JapanAalborg University, Denmark

Tokyo Institute of Technology, Japan

Handset MIMO antenna measurementusing a Spatial Fading Emulator

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Principle of the emulatorWaves coming from the same direction are affectedby the same Doppler effect, regardless of delay time.We can give a Doppler effect to all the waves in the same directionusing one phase shifter. A phase shifter in the RF band enables us to evaluate antenna performanceof a handset array excluding demodulator performance.

#1#31

#2

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r=1.5m #30

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Configuration

Proposed spatial fading emulator

Multipath environmentUniform distributionNon-uniform angular power spectrum (APS)

Computer

PowerDivider Transmitter

Receiver

Attenuator PhaseShifter

Scattering unit

D/AConverter Computer

PowerDivider Transmitter

Receiver

Attenuator PhaseShifter

Scattering unit

D/AConverter

The scattering unit are arranged around the handset antenna. Waves radiated from the scattering units can produce a multipath environment.

Phase shifter in the RF band can directly vary phase of the RF signalaccording to a Doppler frequency to perform a moving test for a handset.

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M base station (BS) antennas create a set of M uncorrelated waves.M uncorrelated waves comprises Qc clusters surrounding aroundN handset antennas moving toward the azimuth direction, φ0.

n=1 N

Moving direction

k=1

Km

RX

k

scatterer

m

m=1 M

TXCluster q=1

q

Qc

n=1 N

Moving direction

k=1

Km

RX

k

scatterer

m

m=1 M

TX

m=1 M

TXCluster q=1

q

Qc

Channel model of M-by-N MIMO system

φ0

Scenario for MIMO channel

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Purpose

The purpose is to confirm effectiveness of the RF-controlled spatial fading emulator in MIMO OTAwith regard to antenna measurement and handset evaluation.

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Handset antennas

For antenna evaluation, we made a comparison between MIMO channelcapacities of a radio propagation test and OTA testing using the emulator.we used four types of handset antennas.

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(A) (B) (C) (D)

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Radio propagation test

Base station

Mobile terminal

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②

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The MIMO propagation test was conducted in a central areaof a downtown in Aalborg city in Denmark.The handset antenna was set on a car trailer to be moved along the test route.Radio frequency was 2.35 GHz.

We used the experimental data along the route 4.

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Channel model for the emulator

We used angular power spectrum (APS) of incoming waveswith a Laplacian distribution in the same manner as the spatial channel model (SCM) of 3GPP.

Model for spatial cluster

( ) ( )⎪⎭

⎪⎬⎫

⎪⎩

⎪⎨⎧ −−=

σμφ

σθδφθ φ

θ exp21,p

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μφ and σ are 0 and 35 degrees.

The XPR is set at 9 dB.

•Number of scattering unit: 31

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MIMO channel capacity

(A) (B) (C) (D)

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A B C DAntenna type

MIM

O c

apac

ity [b

ps/H

z]

Propagation testEmulator

The MIMO channel capacities of the OTA testing are in good agreementwith those of the propagation test.

The emulator is effective in evaluating the MIMO antenna by the agreementbetween the data obtained from the emulator and the propagation test.

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2-by-2 MIMO measurement system

For handset evaluation, we have constructed measurement system with a delay wave using a set of WLAN radio transceivers.The two digital fading simulators are used only for producing delayprofile of the incoming waves.

MS#1#2

WAP#1#2

ATTATT

ATTATT

Downlink

Uplink

DFSDiv.VPA.

Anechoic chamber

Servercomputer

Clientcomputer

Phaseshifter

Attenuator

Circulator

LO

Circulator Isolator

Spatial fading emulator for a 2-by-2 MIMO wireless LAN system

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Measured throughput vs. delay time (fd=6Hz)The MIMO throughput is almost similar to SISO in the case of fd = 6Hz because the lowthroughput causes a change of the transmission method from MIMO to SISO.The advantage of the MIMO configuration is obtained by only the maximum ratio combining (MRC) diversity effect.

One delay wave with the same power as the direct wave.

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Delay [nsec]

TP

[M

bps]

fd=6HzWith delay

MIMOSISOMIMOSISO

Dipole array

Radio frequency: 2.412 GHz.

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I presented an effectiveness of the RF-controlled spatial fading emulator with regard to both antenna measurment

and handset evaluation.

For antenna evaluation, the agreement between MIMO characteristics in the propagation test and OTA testing reveals that the emulator is effective in evaluating handset antennas.

With respect to handset evaluation, we have made a start ofthe MIMO throughput measurement using the emulator.

Conclusion