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)
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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)
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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
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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
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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)
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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
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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]
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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.
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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.
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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]
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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
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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.
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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