1. Hitachi Ltd. 1 Hitachi Technical Approaches for Future RAN Evolution 3GPP2 Air 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.

2. Hitachi Ltd. 2 Hitachi Technical Approaches for Future RAN Evolution 3GPP2 Air Interface Evolution(AIE) - Technical Experts Meeting(TEM), 10-11 March 2005, Denver, USA Hitachi, Ltd.

3. Hitachi Ltd. 3 0.01 0.1 1 10 Spectral Efficiency [bit/s/Hz] 100203040 Eb/No [dB] IS-95 CDMA 1x GSM AMPS 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]

4. Hitachi Ltd. 4 Requirement : 4 [bit/s/Hz] 0.01 0.1 1 10 Spectral Efficiency [bit/s/Hz] 100203040 Eb/No [dB] IS-95 GSM 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 1x EVDO Shannon limit EVDO (~Peak rate)

5. Hitachi Ltd. 5 Shannon limit Requirement : 4 [bit/s/Hz] 0.01 0.1 1 10 Spectral Efficiency [bit/s/Hz] 100203040 Eb/No [dB] IS-95 GSM 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 1x EVDO EVDO (~Peak rate) Interference bound (Freq. reuse = 1)

6. Hitachi Ltd. 6 Requirement : 4 [bit/s/Hz] 0.01 0.1 1 10 Spectral Efficiency [bit/s/Hz] 100203040 Eb/No [dB] IS-95 GSM AMPS CDMA 1x EVDO EVDO (~Peak rate) Two types of air interface evolutions are needed. To achieve requirement 2: Interference Reduction 1: Spatial Multiplexing Target

7. Hitachi Ltd. 7 0.1 1 10 100 Spectral Efficiency [bit/s/Hz] 40100203040 Eb/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

8. Hitachi Ltd. 8 0.1 1 10 100 Spectral Efficiency [bit/s/Hz] 40100203040 Eb/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

9. Hitachi Ltd. 9 x12 x6 x3 x2 x1 0.1 1 10 100 Spectral Efficiency [bit/s/Hz] 40100203040 Eb/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

10. Hitachi Ltd. 10 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 number of antennas per MS). Need to select combination of spatial multiplexing and interference reduction. Spatial multiplexing around 6 seems to be good. 1 2 3 6 12 20dB 14dB 10dB 6dB 3dB12 1100 252 310 66 BS (*1) MS (*2) Interference Reduction Spatial Multiplexing Antennas (ideal case) 1MS with 2antennas (MIMO case) 2MSs with 1antenna (SDMA case)

11. Hitachi Ltd. 11 Spatial Multiplexing SDMA MS Spatially 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.

12. Hitachi Ltd. 12 Directional Gain [dB] 0 -5 -10 -15 -20 -25 -30 -35 -40 -150 -120 -90 -60 -300 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

13. Hitachi Ltd. 13 Omni BS # of activated beams simultaneously Spectral Efficiency with SDMA 12345 Spectral Efficiency [bit/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] 0510-10 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]

14. Hitachi Ltd. 14 x12 x6 x3 x2 x1 0.1 1 10 100 Spectral Efficiency [bit/s/Hz] 40100203040 Eb/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.

15. Hitachi Ltd. 15 BS cooperation CDF of Ec/Io shows increasing interference due to beam collision and therefore effects of spatial multiplexing are saturated. BS cooperation approach can reduce probability of beam collision and reduce inter-cell interference[4]. BS1 BS2 Receive data from BS2-beam3 without interference Receive data from BS1-beam4 without 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.

16. Hitachi Ltd. 16 Omni BS # of activated beams simultaneously Spectral Efficiency CDF of Ec/Io without BS cooperation with BS cooperation Simulation Results : Effect of BS cooperation 123456 Spectral Efficiency [bit/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] 0510-10 0.0 1.0 0.8 0.6 0.4 0.2 Omni BS without BS cooperation with BS cooperation ~3.6 [bit/s/Hz] ~1.9 [bit/s/Hz]

17. Hitachi Ltd. 17 x12 x6 x3 x2 x1 0.1 1 10 100 Spectral Efficiency [bit/s/Hz] 40100203040 Eb/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 SDMA with BS cooperation Additional 2x2 MIMO

18. Hitachi Ltd. 18 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.

19. Hitachi Ltd. 19 References “Hitachi Requirements for Future RAN Evolution”, 3GPP2 Air Interface Evolution Technical Experts Meeting, March 2005 http://www.cdg.org/technology/cdma_technology/capacity/ca pacity_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