1. Date:03 June, 2009 Abstract: This contribution contains detailed proposal for implementing subband OFDMA in DO Rev. C 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. OFDMA Multiuser Interlace and Preamble for DO Rev. C Recommendation : Review and Adopt Source:Shu Wang VIA Telecom Contact:shuwang@via-telecom.comshuwang@via-telecom.com C30-20090603-004

2. OFDMA Multiuser Interlace and Preamble for DO Rev. C Shu Wang shuwang@via-telecom.com VIA Telecom

3. Proposal Highlights Flexible Preamble for OFDMA Multiuser Interlace.  The transmission of MIMO/OFDM interlace or OFDMA multiuser Interlace is indicated through common spatial pilots.  No change on the existing dedicated spatial pilots (DSP) design for single-band OFDM Interlace.  For OFDMA multiuser interlace, one additional OFDMA preamble is sent to signal the served ATs in the same interlace. No change on RL DRC reporting.

4. Introduction CDM DO capacity is known to be interference limited.  Though CDM with IC is capacity-approaching, the implementation is challenging, especially on FL. OFDMA helps bring new dimensions in optimizing DO network.  Frequency selectivity gain for better packing efficiency.  Subband interference avoidance for better cell-edge user experience.  Additional scheduling flexibility for improving the balance between VoIP capacity and sector throughput. For implementing OFDMA in DO Rev. C, OFDMA multiuser interlace and preamble design are proposed.

5. Considerations for Frame Structure Upgrade In DO Rev. A/B, the data portion in each interlace can be  Unicast data as in traditional EV-DO, IS-856  Broadcast/Multicast data, CDM or OFDM The existing EV-DO Rev. A/B forward link frame structure and pilot pattern shall be maintained for the strictly backward compatibility. For DO Rev. C, it is recommended to replace a certain number of DO Rev. A/B interlaces with either DO Rev. C CDM interlaces or DO Rev. C OFDM Interlaces.

6. Qualcomm MIMO/OFDM Single-User Packet With MIMO single-user packet (SUP), the whole bandwidth is used to serve one AT or one packet in each interlace. The common spatial pilots (CSPs) are transmitted without beamforming.  CSP is divided into N layers,max subsets of pilots each contains N csp pilots.  the power spectral density on CSPs is a parameter with a nominal value of 1% of the total power per antenna element. The dedicated spatial pilots (DSP) are used to indicates which AT is served and help the demodulation of MIMO signals.  In the existing Qualcomm’s design, only one DSP pattern is used in each interlace. The preamble overhead is a function of requested DRC with up to 4 layers transmission.

7. Subband OFDMA Multiuser Interlace There is a tradeoff between control overhead and achievable performance in terms of throughput and delay. One MAC-ID preamble is enough to signal the AT to be served at either high throughput or low delay region. For a balance in between, it is necessary to serve more than one ATs in the same interlace. For better support of both high-data rate AT/services and delay- sensitive ATs/services, it is necessary for AN to serve multiple ATs in one interlace.  OFDMA is a way for efficiently multiplexing more than one ATs in single interlace.  A flexible preamble design is necessary to accommodate the dynamic nature of multiuser scheduling.

8. DO Preambles In DO Rev. A/B, the preamble is a Walsh sequence which is TDM’d with traffic channel. In DO Rev. C OFDM, the MIMO preamble is proposed to be signalled through OFDM dedicated spatial pilots (DSPs) instead.  The preamble information is the 8 bits MAC-ID and potentially 2 extra bits for rate indicator.  In DO Rev. C OFDM-MIMO, the DRCs are defined for every rank.  If the signalled (DRC, M) is below TH DRC, only the 8-bit MAC-ID is signalled. In the proposed DO Rev. C OFDMA interlace, more than one MAC- ID will be transmitted to signal all served ATs in the same interlace.  For each OFDM subband, one MAC-ID is used to indicate either a single-user packet or a DO Rev. A/B multiuser packet to be sent in this subband.  For single-user MIMO/OFDM, one MAC-ID with optional 2-bit rate indicator is enough to signal the AT to be served.  For Multiuser MIMO or SDMA, two MAC-IDs with optional 2-bit rate indicator are necessary to signal the two ATs to be served.

9. Subband OFDMA Preamble Overview OFDMA Pattern Indication. It is coded and signaled through the location of common spatial pilots (CSPs).  CSP is sent with a nominal value of 1% of the total power per antenna element.  It is proposed to signal 3 additional subband patterns in addition to the existing Qualcomm’s single-band MIMO/OFDM OFDMA Preamble. Every OFDMA preamble containing a 8-bit MAC- ID and an optional 2-bit rate indicator is coded and sent through one set of DSPs in the first slot to indicate the AT(s) to be served in the interlace.  Each OFDMA preamble is sent through 120 OFDM tones. It is 15 OFDM tones per OFDM symbol with 4 OFDM symbols per slot.  It takes 15/180 = 1/12 of Tx power for every 8 or 10 bits of each preamble.  One additional OFDMA preamble is sent through another set of tone positions to support Subband OFDMA and Multiuser MIMO.

10. Subband OFDMA Pattern (1/2) A 3-bit interlace type indicator, OFDMA_PATTERN, indicates the subband allocation information for the next or current interlace.  OFDMA_PATTERN = ‘000’ – single-band OFDM/MIMO  OFDMA_PATTERN = ‘001’ – subband OFDMA/MIMO with two equal subbands.  OFDMA_PATTERN = ‘010’ -- subband OFDMA/MIMO with one subband of one ¼ bandwidth and one subband of three ¼ bandwidth.  OFDMA_PATTERN = ‘011’ – two-user OFDM/MIMO or SDMA.  The other values are reversed Only two-subband OFDMA pattern is proposed for each carrier. The granularity of MIMO/OFDM is improved from one interlace (about 25% of DO FL channel resource) to ¼ of interlace (about 6.25% of DO FL channel resource).

11. Subband OFDMA Pattern (2/2)

12. OFDMA Preambles (1/2) The AT assignment is signalled through OFDMA preambles sent in the first slot of the OFDMA interlace.  For a single-user OFDM interlace, only one OFDMA preamble is transmitted in the first slot.  For a multiuser OFDMA interlace, two preambles are sent in the first slot. Each OFDMA preamble are carried through one set of pilots, which is either layer 1 DSPs if MIMO is used, or OFDMA pilots if no MIMO AT is scheduled.  The OFDMA pilots share the same pattern and modulation as the layer 1 DSPs.  Each set of the OFDMA pilot has 120 OFDM tones evenly distributed in the 4 symbols of the first slot of each interlace.  Each set of the OFDM pilots carries a 8-bit MAC ID. The DSP tones for each OFDMA preamble are equi-spaced for better channel estimation and are randomly allocated across sectors.  Pilot offset f: The position of the first pilot tone on the first layer, which is a function of Sector ID and the MAC-ID of the first subband or the first served AT.  DSP size j(M): The number of DSP per layer, for instance, 10 for M=3  DSP spacing q(M): 180 / j(M )  DPS location DSP(n,m): Tone locations for layer n in OFDM symbol m The transmitted modulation symbols on DSPs are scrambled with a pseudo-random sequence that is a function of  sector ID,  slot index,  sub-packet index,  the served user preamble information, which a 8-bit MAC-ID and an optional 2-bit rate indicator.  the layer index (n).

13. OFDMA Preambles (2/2) In each subband, the transmitted packet can be either a MIMO/OFDM packet or a non-MIMO OFDM packet.  A non-MIMO OFDM packet may be either a single-user OFDM packet or a multiuser OFDM packet. MIMO DSP spacing is 12 tones when the rank is 1, 6 tones when the rank is 2 or 3, and 5 tones when the rank is 4. The offset between OFDMA pilot tones is around 3 when the subband size is 2.

14. Summary Subband OFDMA multiuser packeting can help increase the spectral efficiency of DO networks. The subband OFDMA multiuser packet preamble is embedded in the common spatial pilots and dedicated spatial pilots.  It uses the common spatial pilots to signal subband allocation.  It uses the dedicated spatial pilots in the first slot to signal the AT assignment.  No change on DRC reporting.