doc.: IEEE 802.15-15-0667-01-hrrc

Submission

September 2015

Junhyeong Kim, ETRI Slide 1

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Submission Title: [A Study on mmWave Beamforming for High-Speed Train Communication]

Date Submitted: [13 September, 2015]

Source: [Junhyeong Kim, Bing Hui, Hee-Sang Chung, JunHwan Lee] Company [ETRI]

Address [218 Gajeong-ro, Yuseong-gu, Daejeon, 305-700, KOREA]

Voice:[+82-42-860-6239], FAX: [+82-42-860-6732], E-Mail:[jhkim41jf@etri.re.kr]

Abstract: [A Study on mmWave Beamforming for High-Speed Train Communication]

Purpose: [For discussion]

Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for

discussion and is not binding on the contributing individual(s) or organization(s). The material in this

document is subject to change in form and content after further study. The contributor(s) reserve(s) the right

to add, amend or withdraw material contained herein.

Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE

and may be made publicly available by P802.15.

doc.: IEEE 802.15-15-0667-01-hrrc

Submission

Contents

• Introduction

• Network Structure

• Beamforming

• Simulation

• Conclusions

• References

Junhyeong Kim, ETRI Slide 2

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

Submission

Introduction

• Hierarchical two-hop network for fast moving vehicles

– Mobile wireless backhaul link • High rate rail communications Interest Group (IG HRRC) : a multi-gigabit-per-

second mobile wireless backhaul supporting high-mobility up to 500km/h

– Access link • Small cell (Wi-Fi and femto cell)

Junhyeong Kim, ETRI Slide 3

DU

GW

Public Internet

RU

GW : Gateway

DU : Digital Unit

RU : Radio Unit

TE : Terminal Equipment

RU

TE

Backhaul Link

mmWave

Backhaul Link

mmWave

Access Link

(inside vehicle)

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

Submission

Introduction

• Various technical challenges and potential solutions

– Capacity improvement • Millimeter-wave due to its vast amount of underutilized spectrum

• MIMO techniques (polarized antenna)

– Path loss and atmospheric attenuation of millimeter-wave • coverage improvement by using beam-forming technique

– Inter-carrier interference (ICI) by Doppler effect • Proper sub-carrier spacing design for OFDM

• Millimeter-wave beam-forming techniques Doppler frequency shift in the

frequency domain can be simply overcome by automatic frequency control (AFC)

Junhyeong Kim, ETRI Slide 4

ETRI’s approach to physical layer design

Mobile Wireless Backhaul Link

(Outside Vehicle)

OFDM based on mmWave

Beamforming (2-link multi-flow)

Data throughput (DL) 2 Gbps using 500-MHz bandwidth

Spectral efficiency 4 bps/Hz

Mobility Support 500 km/h

User Access Link (Inside Vehicle) WiFi or Femto

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

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Network Structure

• Millimeter-wave beamforming for HST

communication

– Dual link multi-flow : same radio resources (time and

frequency) are assigned to both links

Junhyeong Kim, ETRI Slide 5

z

y

x(0, 0, 0)

fixed BF

adaptive BF

optical fiber

X2 interface

Public Internet

... ...

GW

DU #d+1DU #d

D-RU #mD-RU #m-1 D-RU #m+2D-RU #m+1 D-RU #m+4D-RU #m+3

direction of movement

T-RU #1 T-RU #2

z'

y'x'

DRUd DRUd

TRUd

DRU trackd

DRUh

TRUh

(0, dDRU-track, hDRU) (dDRU, dDRU-track, hDRU) (2 dDRU, dDRU-track, hDRU)

HST : (0, 0, 0) (x, 0, 0),

T-RU #1 (-dTRU/2, 0, hTRU) (-dTRU/2+x, 0, hTRU)

T-RU #2 (dTRU/2, 0, hTRU) (dTRU/2+x, 0, hTRU)

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

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Beamforming

• 3D beam radiation pattern

– Horizontal and vertical beam width (3dB) : approximately 8

degrees

– Maximum beamforming gain : 21.58 dBi

Junhyeong Kim, ETRI Slide 6

-200 -150 -100 -50 0 50 100 150 200-40

-30

-20

-10

0

10

20

30Beam Radiation Pattern

Degree ()

Gai

n (

dB

i)

=0

=90z

yx

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

Submission

Beamforming

• Adaptive BF : require automatic tracking of signals of moving

targets by continuously updating their parameters based on the

received signals

– Control the beam direction with an accuracy 1˚

– Beam radiation pattern remains unchanged during beam steering

Junhyeong Kim, ETRI Slide 7

z

y

x(0, 0, 0)

optical fiber

X2 interface

Public Internet

... ...

GW

DU #d+1DU #d

direction of movement

z'

y'x'

DRUd DRUd

TRUd

DRU trackd

HST : (0, 0, 0) (x, 0, 0),

T-RU #1 (-dTRU/2, 0, hTRU) (-dTRU/2+x, 0, hTRU)

T-RU #2 (dTRU/2, 0, hTRU) (dTRU/2+x, 0, hTRU)

(dDRU, dDRU-track, hDRU) (2 dDRU, dDRU-track, hDRU)

DRUh

(0, dDRU-track, hDRU) D-RU #mD-RU #m-1 D-RU #m+2D-RU #m+1 D-RU #m+4D-RU #m+3

TRUh

T-RU #1 T-RU #2

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

Submission

Beamforming

• Fixed BF : BF parameters are fixed

– In the case of TX, the beam direction of m-th D-RU and m+1-th D-

RU is (dRU/2, 0, 0) and the beam direction of m+2-th D-RU and

m+3-th D-RU is (3∙dRU/2, 0, 0)

– In the case of RX, the beam directions of T-RU 1 and T-RU 2 are

simply set to direct in the negative and positive direction of the x-

axis respectively

Junhyeong Kim, ETRI Slide 8

z

y

x(0, 0, 0)

optical fiber

X2 interface

Public Internet

... ...

GW

DU #d+1DU #d

direction of movement

z'

y'x'

DRUd DRUd

TRUd

DRU trackd

HST : (0, 0, 0) (x, 0, 0),

T-RU #1 (-dTRU/2, 0, hTRU) (-dTRU/2+x, 0, hTRU)

T-RU #2 (dTRU/2, 0, hTRU) (dTRU/2+x, 0, hTRU)

(dDRU, dDRU-track, hDRU) (2 dDRU, dDRU-track, hDRU)

DRUh

(0, dDRU-track, hDRU) D-RU #mD-RU #m-1 D-RU #m+2D-RU #m+1 D-RU #m+4D-RU #m+3

TRUh

T-RU #1 T-RU #2

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

Submission

Simulation

• Simulation scenarios

– adaptive BF (BS) + adaptive BF (TE)

– fixed BF (BS) + fixed BF (TE)

– fixed BF (BS) + adaptive BF (TE)

• Performance evaluation

– received signal quality

• 𝑆𝐼𝑁𝑅𝑑𝐵 1 = 10𝑙𝑜𝑔10𝑆𝑁𝑅 1,1

𝑆𝑁𝑅 2,1 +1, 𝑆𝐼𝑁𝑅𝑑𝐵 2 = 10𝑙𝑜𝑔10

𝑆𝑁𝑅 2,2

𝑆𝑁𝑅 1,2 +1

– 𝑆𝐼𝑁𝑅 𝑛 =𝑃𝑅𝑋,𝐷 𝑛

𝑃𝑅𝑋,𝐼 𝑛 +𝑁𝐹𝐿 𝑛=

𝑆𝑁𝑅𝐷 𝑛

𝑆𝑁𝑅𝐼 𝑛 +1

– 𝑆𝑁𝑅𝑑𝐵 𝑚, 𝑛 = 𝑅𝑆𝑆𝑑𝐵𝑚 𝑚, 𝑛 − 𝑁𝐹𝐿,𝑑𝐵𝑚(𝑛)

– 𝑅𝑆𝑆𝑑𝐵𝑚 𝑚, 𝑛 = 𝑃𝑇𝑋,𝑑𝐵𝑚 𝑚 + 𝐺𝑇𝑋,𝑑𝐵𝑖 𝑚, 𝑛 + 𝐺𝑇𝑋,𝑑𝐵𝑖 𝑚, 𝑛

– 𝑁𝐹𝐿,𝑑𝐵𝑚 𝑛 = −174 + 𝑁𝐹,𝑑𝐵 + 10𝑙𝑜𝑔10(𝑊)

Junhyeong Kim, ETRI Slide 9

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

Submission

Simulation

• Major parameters

Junhyeong Kim, ETRI Slide 10

Parameters Values

Carrier frequency fc = 32 GHz

System bandwidth W = 125 MHz

Transmit power PTX,dBm = 20 dBm

Free space path loss [1] PLdB = 92.4 + 20 log fc,GHz

+ 20 log dkm (dB)

Noise figure NF,dB = 8 dB

D-RU height hDRU = 10 m

T-RU height hTRU = 3 m

Distance between

adjacent D-RUs dDRU = 1000 m

Distance between

adjacent T-RUs dTRU = 200 m

Distance between

Railway track and D-RUs

dDRU-track ∈

{10, 50, 100, 150} m

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

Submission

Simulation

• Simulation results : received signal quality

– As the HST moves far away from the D-RU, the effect of

adaptive BF is negligible whereas it is important to use

adaptive BF if the T-RU is close to D-RU

Junhyeong Kim, ETRI Slide 11

0 100 200 300 400 500 600 700 800 900 1000-60

-40

-20

0

20

40

60SINR of Received Signal

HST Location (m)

SIN

R (

dB

)

TRU #1 (FXD TX BF, FXD RX BF)

TRU #2 (FXD TX BF, FXD RX BF)

TRU #1 (ADP TX BF, ADP RX BF)

TRU #2 (ADP TX BF, ADP RX BF)

TRU #1 (FXD TX BF, ADP RX BF)

TRU #2 (FXD TX BF, ADP RX BF)

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

Submission

Simulation

• Simulation results : received signal quality

– Received signal strength < 2 dB in the HST location from

200m to 800m

• If the T-RUs are placed sufficiently far away from each other, inter-D-RU

interference at each T-RU is significantly reduced with a properly sharp

beam pattern designed for both TX and RX side

Junhyeong Kim, ETRI Slide 12

0 100 200 300 400 500 600 700 800 900 10000

2

4

6

8

10

12

14

16

18Degradation of Received Signal Strength

HST Location (m)

Deg

radat

ion (

dB

)

TRU #1 (FXD TX BF, FXD RX BF)

TRU #2 (FXD TX BF, FXD RX BF)

TRU #1 (ADP TX BF, ADP RX BF)

TRU #2 (ADP TX BF, ADP RX BF)

TRU #1 (FXD TX BF, ADP RX BF)

TRU #2 (FXD TX BF, ADP RX BF)

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

Submission

Simulation

• Simulation results : AoD, AoA

– Both vary according to 𝑑𝐷𝑅𝑈−𝑡𝑟𝑎𝑐𝑘

– 𝑑𝐷𝑅𝑈−𝑡𝑟𝑎𝑐𝑘 : distance between DRU and railway track

Junhyeong Kim, ETRI Slide 13

0 100 200 300 400 500 600 700 800 900 10000

50

100

150

200Angle of Departure (Transmit Beamforming)

HST Location (m)

(

Deg

ree)

0 100 200 300 400 500 600 700 800 900 10000

50

100

150

200Angle of Arrival (Receive Beamforming)

HST Location (m)

(

Deg

ree)

dDRU-track

=10m

dDRU-track

=50m

dDRU-track

=100m

dDRU-track

=150m

• AoD : Angle of Departure

(transmit beamforming)

• AoA : Angle of Arrival

(receive beamforming)

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

Submission

Simulation

• Simulation results

– 𝑑𝐷𝑅𝑈−𝑡𝑟𝑎𝑐𝑘 = 10 𝑚

Junhyeong Kim, ETRI Slide 14

0 100 200 300 400 500 600 700 800 900 10000

50

100

150

200Zenith Angle ()

HST Location (m)

Angle

(D

egre

e)

AoD (TX BF)

AoA (RX BF)

0 100 200 300 400 500 600 700 800 900 1000-100

0

100

200Azimuth Angle ()

HST Location (m)

Angle

(D

egre

e)

0 2 4 6 8 10 12 14 16 18 20105

110

115

120

HST moves from (94,0,0) meters to (104,0,0) meters

Velocity of HST = 400 km/h

Zenith Angle ()

Elapsed Time (msec)A

ngle

(D

egre

e)

AoD

AoA

AoD (round-off)

AoA (round-off)

0 2 4 6 8 10 12 14 16 18 20-20

0

20

40

60Azimuth Angle ()

Elapsed Time (msec)

Angle

(D

egre

e)

• AoD : Angle of Departure

(transmit beamforming)

• AoA : Angle of Arrival

(receive beamforming)

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

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Conclusions

• Different BF schemes are appropriate for different

HST location

• The fixed BF can achieve very similar performance to

that of adaptive BF in most of time

– giving a valuable insight into designing the mmWave BF

based HST communication system from feasibility and

implementation perspective

• As future works, it is worth to study the performance

of adaptive BF in the presence of calibration error

and the HST communication system in various

environments including the case of HST running

along the curved line.

Junhyeong Kim, ETRI Slide 15

September 2015

doc.: IEEE 802.15-15-0667-01-hrrc

Submission

References

1. ITU-R P.525-2, “Calculation of free-space

attenuation”

Junhyeong Kim, ETRI Slide 16

September 2015