Hitachi Ltd.

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Hitachi Technical Approaches forFuture RAN Evolution

3GPP2Air Interface Evolution(AIE) Technical Experts Meeting(TEM)

10-11 March 2005, Denver, USA Hitachi, Ltd.

©2005 Hitachi, Ltd. All rights reserved.Hitachi grants a free, irrevocable license to 3GPP2 and its Organizational Partners to incorporate text or other copyrightable material contained in the contribution and any modifications thereof in the creation of 3GPP2 publications; to copyright and sell in Organizational Partner's name any Organizational Partner's standards publication even though it may include all or portions of this contribution; and at the Organizational Partner's sole discretion to permit others to reproduce in whole or in part such contribution or the resulting Organizational Partner's standards publication. The contributors are also willing to grant licenses under such contributor copyrights to third parties on reasonable, non-discriminatory terms and conditions for purpose of practicing an Organizational Partner’s standard which incorporates this contribution.This document has been prepared by Hitachi to assist the development of specifications by 3GPP2. It is proposed to the Committee as a basis for discussion and is not to be construed as a binding proposal on the contributors. The contributors specifically reserve the right to amend or modify the material contained herein and to any intellectual property of the contributors other than provided in the copyright statement above.

Hitachi Ltd.

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HitachiTechnical Approaches for

Future RAN Evolution

3GPP2 Air Interface Evolution(AIE) - Technical Experts Meeting(TEM),

10-11 March 2005, Denver, USA

Hitachi, Ltd.

Hitachi Ltd.

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0.01

0.1

1

10

Spect

ral Effi

ciency

[b

it/s

/Hz]

100 20 30 40Eb/No [dB]

IS-95

CDMA 1x

GSMAMPS

Background To achieve higher data rate, high spectral

efficiency (~4bit/s/Hz) is required[1].

Trend line shows higher efficiency and lower Eb/No are required at future air interface evolution system.

FL receiver performance requirements (fading ch.) [3]

Based on voice user capacity reported at CDG website[2]

EVDO

Requirement : 4 [bit/s/Hz]

Hitachi Ltd.

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Requirement : 4 [bit/s/Hz]

0.01

0.1

1

10

Spect

ral Effi

ciency

[b

it/s

/Hz]

100 20 30 40Eb/No [dB]

IS-95GSM

AMPS

Background Due to Shannon limit, evolution system cannot

follow that trend line.

With EVDO, the trend line turns to higher efficiency with higher Eb/No.

FL receiver performance requirements (fading ch.) [3]

FL receiver performance requirements (AWGN) [3]

Based on voice user capacity reported at CDG website[2]

CDMA 1xEVDO

Shannon limit

EVDO (~Peak rate)

Hitachi Ltd.

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Shannon limit

Requirement : 4 [bit/s/Hz]

0.01

0.1

1

10

Spect

ral Effi

ciency

[b

it/s

/Hz]

100 20 30 40Eb/No [dB]

IS-95GSM

AMPS

Background In cellular systems, inter-cell interference causes

another limitation (Interference bound).

Due to the interference bound, not all user can achieve high efficiency.

FL receiver performance requirements (fading ch.) [3]

FL receiver performance requirements (AWGN) [3]

Based on voice user capacity reported at CDG website[2]

CDMA 1xEVDO

EVDO (~Peak rate)Interference

bound(Freq. reuse = 1)

Hitachi Ltd.

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Requirement : 4 [bit/s/Hz]

0.01

0.1

1

10

Spect

ral Effi

ciency

[b

it/s

/Hz]

100 20 30 40Eb/No [dB]

IS-95GSM

AMPS

CDMA 1xEVDO

EVDO (~Peak rate)

Two types of air interface evolutions are needed.

To achieve requirement

2: Interference Reduction

1: Spatial Multiplexing

Target

Hitachi Ltd.

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0.1

1

10

100

Spect

ral Effi

ciency

[b

it/s

/Hz]

40100 20 30 40Eb/No [dB]

20dB

Requirement : 4 [bit/s/Hz]

Multiplexing vs. Interference Reduction

To achieve requirement, there are some options to combine spatial multiplexing and interference reduction. case 1: without spatial multiplexing

20dB Interference Reduction

Hitachi Ltd.

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0.1

1

10

100

Spect

ral Effi

ciency

[b

it/s

/Hz]

40100 20 30 40Eb/No [dB]

10dB

Requirement : 4 [bit/s/Hz]

Multiplexing vs. Interference Reduction

To achieve requirement, there are some options to combine spatial multiplexing and interference reduction. case 2: x3 spatial multiplexing

10dB Interference Reduction

x3 Spatial Multiplexing

Hitachi Ltd.

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x12x6

x3x2x1

0.1

1

10

100

Spect

ral Effi

ciency

[b

it/s

/Hz]

40100 20 30 40Eb/No [dB]

3dB

6dB

10dB

14dB

20dB

Requirement : 4 [bit/s/Hz]

Multiplexing vs. Interference Reduction

To achieve requirement, there are some options to combine spatial multiplexing and interference reduction. Summary

Hitachi Ltd.

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Multiplexing vs. Interference Reduction

note (*1): In case of full interference reduction can be applied. note (*2): Total number of MS antennas (product of number of MSs by nu

mber of antennas per MS).

Need to select combination of spatial multiplexing and interference reduction.

Spatial multiplexing around 6 seems to be good.

1236

12

20dB14dB10dB6dB3dB 1212

110025 2

31066

BS(*1) MS(*2)

Interference Reduction

Spatial Multiplexing

Antennas (ideal case)

1MS with 2antennas(MIMO case)

2MSs with 1antenna(SDMA case)

Hitachi Ltd.

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Spatial Multiplexing

SDMA

MS

MSSpatially Separated Channel

BS

Increase capacity per cell (spectral efficiency only)

MIMO

BS MS

Rich Scattering Channel

Multiple Antennas required(Separated ~/2)

Increase capacity per user (efficiency & peak rate impact)

Good for Indoor Environment

Good for Cellular Environment

not many can be equipped on handsets.

Hitachi Ltd.

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Dir

ect

ional G

ain

[dB

]

0

-5

-10

-15

-20

-25

-30

-35

-40-150-120 -90 -60 -30 0 30 60 90 120 150

Angle [degree]

#a #b #c #d #e #f#g #h #i #j #k #l Beam IDs

SDMA with fixed beams

Low complexity (beam-pattern selection only). Max. 6 spatial multiplexing using overlapped 12beams (12

antennas).

SDMA with fixed beam approach

Hitachi Ltd.

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Omni BS

# of activated beams simultaneously

Spectral Efficiency

with SDMA

1 2 3 4 5

Spect

ral Effi

ciency

[b

it/s

/Hz]

1.0

0.0

2.0

3.0

4.0

Simulation Results : Effect of SDMA

CDF of Ec/Io

-5

Ec/Io [dB]0 5 10-10

0.0

1.0

0.8

0.6

0.4

0.2

Omni BS

with SDMA

6

Spectral Efficiency increases but saturated.

~1.9 [bit/s/Hz]

Hitachi Ltd.

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x12x6

x3x2x1

0.1

1

10

100

Spect

ral Effi

ciency

[b

it/s

/Hz]

40100 20 30 40Eb/No [dB]

3dB

6dB

10dB

14dB

20dB

Requirement : 4 [bit/s/Hz]

Effect of SDMA

~ 6dB interference reduction and x3 multiplexing.

Achieve ~1.9[bit/s/Hz].

~10dB interference reduction and x2 multiplexing.

Some additional improvements are needed:

Effect of SDMA

~ 1dB interference reduction and x6 multiplexing.

Hitachi Ltd.

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BS cooperation CDF of Ec/Io shows increasing interference due to beam collision and th

erefore effects of spatial multiplexing are saturated. BS cooperation approach can reduce probability of beam collision and re

duce inter-cell interference[4].

BS1 BS2

Receive data fromBS2-beam3without interference

Receive data fromBS1-beam4without interference

Interference due to beam collision

Exchange beam schedule

1

2

3

4

1

2

3

4 MS1

MS2

MS3

Each MS measures and reports which beam cause inter-cell interference. BSs make schedules in cooperation to avoid beam collision.

Hitachi Ltd.

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Omni BS

# of activated beams simultaneously

Spectral Efficiency CDF of Ec/Io

without BS cooperation

with BS cooperation

Simulation Results : Effect of BS cooperation

1 2 3 4 5 6

Spect

ral Effi

ciency

[b

it/s

/Hz]

1.0

0.0

2.0

3.0

4.0

Achieve efficiency nearly direct proportion to number of beams. Avoid collisions and reduced probability of lower Ec/Io cases.

-5

Ec/Io [dB]0 5 10-10

0.0

1.0

0.8

0.6

0.4

0.2

Omni BS

without BS cooperation

with BScooperation

~3.6 [bit/s/Hz]

~1.9 [bit/s/Hz]

Hitachi Ltd.

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x12x6

x3x2x1

0.1

1

10

100

Spect

ral Effi

ciency

[b

it/s

/Hz]

40100 20 30 40Eb/No [dB]

3dB

6dB

10dB

14dB

20dB

Requirement : 4 [bit/s/Hz]

Effect of SDMA with BS cooperation

Very close to requirement (~3.6[bit/s/Hz]) Can achieve requirement with additional 2x2 MIMO.

Effect of SDMAwith BS cooperation

Additional 2x2 MIMO

Hitachi Ltd.

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Conclusion

From the viewpoint of spectral efficiency, spatial multiplexing and interference reduction are key features of future air interface evolution systems.

To achieve requirement(4bit/s/Hz), BS cooperation SDMA with additional 2x2 MIMO is good selection. So, signals for SDMA, MIMO, and BS cooperation are needed for future air interface evolution systems.

Hitachi Ltd.

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References“Hitachi Requirements for Future RAN Evolution”, 3GPP2 Air Interface Evolution Technical Experts Meeting, March 2005

http://www.cdg.org/technology/cdma_technology/capacity/capacity_comparison_paper.asp, CDMA Development Group

“Recommended Minimum Performance Standards for cdma2000 Spread Spectrum Base Stations Release C”, 3GPP2 C.S0010-C, January 2005

“A Study of Space-Time Packet Scheduler with Exchanging Beam Schedule Information”, Proc. of IEEE VTC 2004-Fall, September 2004

[1] [2] [3] [4]

This work was partly supported by National Institute of Information and Communications Technology (NICT).

Acknowledgment