1. Date:11 May, 2009 Abstract: This contribution contains the recommendations for DO Rev. C FL MIMO Notice Contributors grant 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. 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 contributors 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 Contributors. Contributors specifically reserves the right to amend or modify the material contained herein and nothing herein shall be construed as conferring or offering licenses or rights with respect to any intellectual property of Contributors other than provided in the copyright statement above. Recommendations for DO Rev. C FL MIMO Recommendation : review and adopt Source:Shu Wang VIA Telecom Contact:shuwang@via-telecom.comshuwang@via-telecom.com C30-20090511-030

2. Recommendations for DO Rev. C MIMO Shu Wang shuwang@via-telecom.com VIA Telecom

3. Recommendation for DO Rev. C MIMO/OFDMA Antenna Configurations:  Forward Link  Baseline: 2x2 or 4x2  Optional: 4x4  Reverse Link  Baseline: 1x2 or 1x4  Optional: 2x2 or 2x4 MIMO Techniques:  Single-User MIMO  per N x 307.2kHz and interlace with N = 1, 2,3, 4.  When N=4, it is single-user OFDM-MIMO  Multiuser OFDM-MIMO  per 1.2288MHz and interlace Benefits  Increase user capacity  Improve sector throughput

4. Introduction In theory, the achievable capacity of a MIMO channel grows linearly with the minimum of transmit and receive antenna sizes. In reality, the achievable spatial multiplexing gain of a 1.2288Hz depends on both channel scatttering and AT antenna array size instead of the geometric limitation, min{ N tx, N rx }. In addition, there is an dilemma between sector throughput and VoIP user capacity in FL.  BE throughput is reduced with the increase of VoIP user capacity. For improving user capacity and sector throughput, it is recommended to include OFDM/OFDMA MIMO techniques into DO Rev. C.  Multiuser OFDM-MIMO for mitigating the rank deficiency issue and improving sector throughput.  Single-User OFDMA- MIMO for providing additional balance between VoIP user capacity and sector throughput

5. The Impact of MIMO on DO VoIP The introduce of CL-MTD may help increase DO VoIP user capacity.  It alleviates the existing RL limitation on VoIP capacity. The introduce of FL-MIMO interlace/subtype might, however, limit DO VoIP user capacity if it is not treated carefully.  A FL MIMO 8-subpack interlace might reduce the scheduling opportunity for up to 32 VoIP ATs.  Assume 2-slot early termination and 8-user MUP for VoIP. Source: Alcatel-Lucent and Qualcomm

6. Multi-ANTenna AT It is non-trivial to “ squeeze ” more and more antennas and RFs into a mobile phone with considering  Power consumption.  Mechanical limitation.  Multiple radio interfaces there already: GPS, bluetooth, WiFi, …  Antenna spacing requirement.  For more spatial diversity gain, the separation should be larger than 0.5λ  For 2GHz, the wavelength is about 15cm or 5.9 inch.  Operating frequency bands. On the other hand, the achievable MIMO channel capacity also depends on the scattering statistics in addition to the antenna configuration.  The scattering statistics is usually quantified or captured by the angular intervals.  The antenna array configuration is characterized by the area or size limitation in the unit of wavelength and the shape.

7. Rank Deficiency Without the limitation of AT size, the achievable spatial multiplexing gain may still be limited by the spatial scattering condition.  In the case of a 4x4 MIMO, the typical rank distribution where less than 1% of the users are able to use rank 4. Most users have either rank 1 or 2. For an AT with the physical size of a few times of wavelength, e.g., about 0.5~3, the achievable spatial multiplexing gain is limited by the angle spread, AT size and C/I ratio.  This is the case for practical multi-antenna mobile devices.  The expected spatial multiplexing gain mostly is less than 3.

8. Challenges and Recommendations This inherent rank deficiency of MIMO channel can be mitigated through extending DO Rev. A/B’s multiuser packet concept and adding  frequency diversity: OFDMA-MIMO  multiuser diversity: multiuser OFDM-MIMO The impact of MIMO on DO Rev. C VoIP capacity can be balanced through finer MIMO transmission granularity.  MIMO block can be transmitted in the unit of one subband of an interlace instead of the whole 1.2288MHz of one interlace. The benefits of extending the multi-user packet packing include  Improve sector throughput  Increase VoIP user capacity in DO Rev. C

9. OFDMA-MIMO Each AT reports DRC for desired subband(s). For example,  For each single-antenna AT, it reports DRC/PMI for each of the four subbands.  For each dual-antenna AT, it reports two DRC/PMI for each of two subbands. Four bits indicate the data rate request and 3 bits indicate the desired serving sector. The channel has 64-ary bi-orthogonal modulation. The DRC is sent on the Walsh codes W 8 32 and W 24 32 and multiplexed on the I and Q branches, which is similar to the DRC report in the MCW mode.

10. Multiuser MIMO Each AT reports DRCs/PMIs for the desired subband(s).  For each single-antenna AT, it reports DRC/PMI for each of the four subbands.  For each dual-antenna AT, it reports two DRC/PMI for each of two subbands. The AN does the MIMO spatial multiplexing based on the PMI feedbacks from multiple ATs.  Optional: transmitted DRCs/PMIs may be broadcasted through FL preamble.

11. Summary We recommend to include the following options into DO Rev. C MIMO.  Single-User MIMO  per N x 307.2kHz and interlace with N = 1, 2,3, or 4.  When N=4, it is single-user OFDM-MIMO  Multiuser OFDM-MIMO  per 1.2288MHz and interlace