Propagation Channel Modeling for Wideband Radio Systems

UEC Tokyo

Propagation Channel Modeling

for Wideband Radio Systems

Yoshio Karasawa

Advanced Wireless Communication research Center (AWCC) University of Electro-Communications (UEC Tokyo)

EuCAP 2014 April 9, 2014

- How to create realistic MIMO propagation environment for OTA measurements -

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Outline

1. Introduction: MIMO and MIMO-OTA

2. Channel Model for MIMO OTA Systems

- Simplified Configuration

- Channel Model

3. Two-Stage Scheme for MIMO Fading Emulator

4. Development of MIMO Fading Emulator

using FPGA

5. Application Examples

6. Conclusion

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Outline




- Channel Model



using FPGA


6. Conclusion

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MIMO Technologies

Tx signal Rx signal Tx array Encoding with

time and space

domain

Rx array Decoding with

time and space

domain

Multi-path propagation

Information theory

and coding theory

Adaptive array and adaptive signal processing

MIMO covers wide

technical areas

Applications are from W-LAN to next-generation mobile wireless systems.

Radiowave Propagation

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Trend of MIMO R&D

○ Transmission scheme

○ System application (from WLAN to LTE-advanced)

○ System development (MU-MIMO, large-scale MIMO)

- Handset-related problem

such as antenna coupling effect

- High needs to the measurement system development

- Insufficient research for MIMO-OTA

- Establishment of standard scheme

○ Establishment of performance evaluation system

for MIMO user terminal (MIMO-OTA)

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We want to evaluate MIMO user terminal performance.

Necessity of evaluation environment

Construction of MIMO-OTA

Measuring System

Reverberation Chamber Type

Hybrid Structure Type

Fading Emulator Type

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MIMO

(Tx)

Fading

Emulator

MIMO

(Tx) MIMO

(Rx)

Two Types of MIMO-OTA Systems

Fading Emulator Type (FE)

MIMO

(Rx)

Reverberation Chamber Type (RC)

Full functions

Higher Construction Cost

Multipath-rich Environment with large delay

Lower Construction Cost

Higher Flexibility

Lower Flexiblility 6

Both have merit and demerit, and I understand there are no almighty method for OTA measurement scheme.

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Outline




- Channel Model



using FPGA


6. Conclusion

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Required Function for MIMO-OTA Measurement System

Tx Rx

Tx-side Spatial Correlation (depending on Angle of Departure)

Delay Profile (Delay Spread)

Doppler Spectrum (Doppler Spread)

Rx-side Spatial Correlation (depending on Angle of Arrival)

Tx Signal Processing (Fading Emulator)

OTA Environment

Real Channel

Generated OTA Channel

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Multipath channel generation

1

M

DUT

1

L

Multiple Output (Receiving Antenna ports : N)

Multiple Input (Transmitting Antenna ports: M)

Probe Antennas: L

9

Fading Emulator-type MIMO OTA System

Multipath environment -Spatial correlation -Doppler spectrum -Delay profile

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M L

M L

NW

(Hadamard

Matrix

connection)

Basic Configuration of Multipath Fading Generation Part

Path-Controlled Scheme

Antenna-Branch-Controlled Scheme

Number of delay units: MLK Number of Rayleigh faders: MLK (K: Number of multipath delays) Almost perfectly controllable Large scale configuration

Number of delay units: LK Number of Doppler shifters: L Flexibly controllable (realization of some functions is limited.) Simplified configuration (easy to FPGA implementation)

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1

M

1

L

Do

pp

ler-

sh

ift a

dd

itio

n

1

L

Walsh-Hadamard code weighting

1

L

Tim

e-i

nva

ria

ble

d

ela

y c

ha

nn

el g

en

era

tio

n

lfD

Delay t

Fixed amplitude

11

Functional Block Configuration of Antenna-Branch-Controlled Scheme

All functional blocks are connected in cascade.

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Channel Model )()(),()( tttt nsHr t

TXdelayDopplerRX )()(),( AHAAH tt tt

LuuuA 21RX

T

21 lNlll uuu u

)cos( 0 lnjkd

ln eu

Channel Characteristics MwwwA 21TX

T

21 mLmmm www w

WH code

K

k

k

k

dalaydelay

1

)( )()( ttt AH

k

k

Lk

k

k

kk

dalay ccc )()(

2

)(

1

)( diag A

tfjtfjtfj LeeeL

t D2D1D 222

Doppler diag1

)( A )cos(D lll

vf

Independent fluctuation for each input signal

Multipath Delay

Doppler shift Generation

Array antenna reception in the case of a linear array without antenna coupling

Received Signal

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Probe antenna arrangement having all different Doppler-shift values

Doppler-shift frequency (Hz)

Am

pli

tud

e Regular arrangement (Synmetric arrangement)

1

13

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Am

pli

tud

e


Regular arrangement with fixed offset

2

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Am

pli

tud

e


Proposed arrangement (double offset) Non symmetrical arrangement for any combination of two antennas

3

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0.0001

0.001

0.01

0.1

1

-50 -40 -30 -20 -10 0 10

Theoretical (uniform)Regular positionFixed offsetProposed allocation

Cum

ulat

ive

proba

bilit

y

Amplitude (dB)

L=8

CDF of Generated signal amplitude

1

2

3

Rayleigh

L=8

Cum

ula

tive

pro

bab

ilit

y

Amplitude (dB) 16

Doppler-shift

l

Am

pli

tud

e

1 Regular

2 Single offset

3 Double offset

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0.0001

0.001

0.01

0.1

1

10-5 0.0001 0.001 0.01 0.1 1 10 100

Generated

Theoretical (iid)

4

3

2

M = N = 4L = 16

1

Cum

ula

tive

pro

bab

ilit

y

Eigenvalue i

Eigenvalue characteristics of 4 x 4 MIMO in i.i.d. condition

17

:~ 41

Eigenvalues of

HAA

where A is channel matrix.

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TXWHdelayWHLWH ___ WWW

Weight Matrix (=Connection Matrix) for realizing independent fluctuations of all delayed paths

+

1

L

Independent Rayleigh fluctuations

Input 1 2

FE

Output 1

Doppler-shifted fixed amplitude delay waves

Tx-port signal connection matrix (MxM)

Delay signal connection matrix (KxK)

Probe antenna weighting matrix (KMxKM) 18

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0.0001

0.001

0.01

0.1

1

-50 -40 -30 -20 -10 0 10

Amplitude (dB)

Cu

mula

tive

pro

bab

ilit

y

#1 (1.0)

#2 (0.8)

#3 (0.6)

#4 (0.4)

#5 (0.2)

#6 (0.1)

M = N = 2L = 8

Generated

Theoretical (iid)

Fig. 13

Amplitude distribution of each generated delay paths

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Outline




- Channel Model



using FPGA


6. Conclusion

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When the chamber space is not sufficiently large to arrange the probe antennas in the chamber, and if the range in one direction is enough, then ….

21

For example, antenna array mounted in a car

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Two-Stage Scheme

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MIMO Fading Emulator

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Outline




- Channel Model



using FPGA


6. Conclusion

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FPGA IC XILINX Virtex 6 LX240T Baseboard XILINX ML605 Input/Output ADC 4DSP FMC104 (14bit) DAC 4DSP FMC204 (16bit) Input ports M 4 Output ports N 4 Signal processing Clock frequency fs 160MHz IF frequency 40MHz Bandwidth 40MHz (max) Propagation parameters Probe antennas L 16 or 32 Delay paths K 8 Maximum delay 50ms (for k=1-6), 200ms (k=7,8) Delay resolution 6.25ns ( when fs =160MHz) Doppler frequency up to10kHz

Specification and Performance of Developed System based on Two-Stage Scheme

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Delay

TX

Co

nn

ecti

on

M

atr

ix

Del

ay

Co

nn

ecti

on

Ma

trix

f

or

k-t

h d

ela

yed

wa

ve

+

+

+

Do

pp

ler

shif

t a

dd

itio

n

RX

Co

nn

ecti

on

Ma

trix

k=1

TXW

RXA

1

M(4)

1

k

K

1

l

L

1

L

1

N(4)

Input Output

)(ts

K

Am

pli

tud

e o

f ea

ch

pro

be a

nte

nn

a

for

k-t

h d

ela

yed

wa

ve

L

)(k

WHw kb

Delay

Delay

Delay

)(tr

kt

DopplerA

k

k

k

l=1

Delay generation

l l

Hilbert Transformation

PC

FPGA Implementation of 4x4 MIMO Fading Emulator

Parameters’ value setting

FPGA 25

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(Size: 28cm×22cm×5cm)

Developed MIMO Fading Emulator with FPGA Implementation

26

All necessary functions to generate multipath environment is implemented in this small box.

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Element pattern pattern and corresponding Doppler spectrum

v v

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Outline




- Channel Model



using FPGA


6. Conclusion

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Intel Centrino Advanced-n 6200WZR-AMPG300NH

AP UE/UT

データ

受信確認

Application Example 1: WLAN (IEEE 802.11n) Throughput Evaluation

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WLAN (AP)

Down Conv.

Down Conv.

MIMO Fading Emulator (FPGA)

Up Conv.

Up Conv.

WLAN (UE)

(5GHz) (40MHz) (5GHz)

Circulator Circulator

ATT

ATT

[down link (40MHz)]

[up link (5GHz)]

PC

Channel-control signal

Tx Data Rx Data

Application Example 1: WLAN (IEEE 802.11n) Throughput Evaluation

AP: BUFFALO WZR-AMPG300NH UE: Intel Centrino Advanced-N 6200 30

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Evaluation Examples

fD=10Hz100Hz

ドップラーを変える

時間

スループット

t=200ns1ms

遅延量を変える

時間

スループット

Change of Doppler spread Change of delay difference

time time

Data rate

Change the Doppler spread Change the Delay Difference Data rate

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300

250

200

150

100500

0

2000

4000

6000

8000

10000

12000

14000

16000

ドップラーシフト[Hz]

スループット[bps]

遅延量

1

Thro

ughp

ut

[b

ps]

Evaluation example in Rayleigh fading environment

32

GI

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No.1No.2 No.3

No.4 No.1 No.2 No.3 No.4

Sleeve antenna: 33mm (0.56)

(a) dr = (1/8) (b) dr = (3/2)

Application 2: Channel Capacity Evaluation in the case of Antenna Coupling and Spatial Correlation

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[deg]

d=(1/8)

d=(1/2)

Each element pattern without coupling

Element Antenna Pattern for N=4

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DUT

Measured Antenna Pattern data

Multiple Input

Multiple Output

RXA

Multipath Multipath Genaration Part

Developed MIMO Fading Emulator

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MIMO Channel Capacity Decrease due to Antenna Coupling

Experiment in RC using actual antenna

Simulation using antenna pattern data

i.i.d. (without SC and AC)

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Conclusions

We discussed a propagation channel model for OTA test

systems.

One of the primary practical advantages of the proposed

scheme is the realization of a flexible MIMO OTA testing

system in a very simplified configuration without the loss of

necessary functions.

Due to the way that the fading functions are configured in a

cascade, an implementation of the scheme into FPGA circuit

is promising from a practical viewpoint.

We showed detailed performance of the FPGA-implemented

fading emulator and a couple of applications of the system to

wireless communication performance evaluations.

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What I want to say is MIMO Fading Emulator/Simulator having all necessary propagation functions can be realized easily without expensive cost.

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Thank you very much for your kind attention!!

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Propagation Channel Modeling for Wideband Radio Systems

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