Date:30 March, 2008 Abstract: This contribution contains framework and components proposal update for DO R. 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. DO Rev. C Proposal Update Recommendation : review and adopt Source:Shu Wang VIA Telecom C

DO Rev. C Proposal Update Shu Wang, VIA Telecom

Outline HRPD Enhancements  Subband OFDMA Multiuser Packet with C/I Sensitive DRC reporting  MIMO OFDMA with Antenna Selection VoIP Capacity Improvements  Improve Delay-Limited Capacity with Frequency Diversity  C/I sensitive DRC report for cell-edge ATs  Subband hopping for high-C/I ATs Cell Edge Performance Improvements  Subband Interference Management.  Dynamic frequency reuse.  AN Macro Diversity.  simple Broadcast Multicast Services

DO Rev. C Air Interface Roadmap: A VIA’s View The adoption of multi-antenna techniques promises to improve the performance of existing DO network infrastructure in a cost efficient way.  Improved link quality: spatial diversity and beamforming  Higher Date rate: spatial multiplexing, multiuser MIMO MIMO OFDMA with antenna selection provides a balance between DO Rev. A/B and the full MIMO DO.  OFDMA can also bring additional dimensions in optimizing DO network when combined with multi-antenna techniques.  It can improve the delay-limited capacity for VoIP-liked services DO Rev. C with MIMO-OFDMA and antenna selection will be more than a spatial extension of DO Rev A/B. The additional layered transmission can help enable the simple cooperation between ANs with minimum impact on the unicast transmission of each AN.

Frequency Diversity (1/2): The Fundamentals Source: D. Tse, P. Viswanath, Fundamentals of Wireless Communication

Frequency Diversity (2/2): Lessons We Learned from Rev. B Using a single queue for N carriers in Rev B, as opposed to N independent queues in Rev A, helps improve the user experience in the presence of frequency-selective (frequency-dependent) fading. This also is very important for VoIP liked applications, where the required data rate for each user is not high but with strict low latency restriction. Source: Airvana/CDG, EV-DO Rev. B white paper.

Subband OFDMA (1/2): Strictly Backward Compatible OFDMA MUP puts the subpackets of multiple users into different subbands.  Differentiate Tx power for the subbands for higher spectral efficiency.  It provides additional support to the ATs on the cell-edge, in bad reception condition or with delay sensitive services, and the single/dual antenna ATs. Subband OFDMA is fully compatible with OFDM DO with additional features  Adaptive DRC reporting:  An AT reports DRCs for each subband only when the C/I is low and subband channel variation is large. Otherwise, a single DRC is reported instead.  An AT can feedback multiple DRCs for multiple subbands based on the MIMO operation mode.  Adaptive OFDMA Preamble: Only the most efficient OFDMA preamble structure is used by the AN, which depends on the employed OFDMA packing method.

Subband OFDMA (1/2): Frequency Reuse Strictly Backward Compatible with DO Rev. 0/A/B Seamlessly Compatible with Other OFDM DO Rev. C Proposals

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.  Operating frequency bands. MIMO with Antenna Selection is a most efficient way to realize the potentials of multi-antenna techniques.  There is little spatial diversity loss, as long as the multiplexing gain is less than a certain threshold.  The spatial multiplexing gain loss can be compensated through frequency diversity.

Reliability/Throughput Tradeoff (1/2): The Fundamentals

Reliability/Throughput Tradeoff (2/2): Implementations and Rank Deficiency In theory, MIMO capacity is achievable with  full-rank beamforming at the transmitter side  successive interference cancellation at the receiver side. There are tradeoffs between SCW and MCW MIMO.  For a signal processing perspective, a SCW receiver is much easier to be implemented. In reality, rank deficiency reduces the achievable throughput when  there is strong correlation between Tx or Rx antennas OR  the Rx antenna number is less than the Tx antenna number. MIMO with OFDMA, frequency selectivity gain is added to mitigate rank deficiency.  A higher throughput is achievable even when rank deficiency happens.

MIMO-OFDMA + Antenna Selection (1/2) Rx antenna selection is a most cost efficient multi- antenna technique to asymptotically achieve the full potentials of MIMO techniques.  It requires fewer RF chains, has less phone design limitation, lower power consumption and lower manufacturing cost. The achievable spectral efficiency can be close to those with full RF chains with following techniques.  Antenna Selection: the AT chooses some antennas for the next Rx/Tx  Beam Selection: the AT selects the best beams and feeds back the PMIs.  Subband Selection: the AT calculates PMIs for each subbands and report back the best several PMIs to AN.

MIMO-OFDMA + Antenna Selection (2/2) Each AT reports DRC for each subband, even in single-antenna or SCW mode, 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 and multiplexed on the I and Q branches, which is similar to the DRC report in the MCW mode.

Delay Sensitive Services CDM DO was designed and optimized for high throughput.  Multiuser diversity scheduling and slow power control with early termination. However, delay-sensitive services may have different requirements on air interface optimization.  One key requirement is to minimize the delays for all served users. Then it is the throughput or user capacity.  As similar in 1x, the users in bad reception condition expect more Tx power while the users in good reception condition may need less Tx power. The achievable throughputs of delay-sensitive services are generally optimized with delay-limited capacity instead of water-filling capacity.  Multiuser diversity can still be the powerful tool improving the throughput. The considerations for optimizing delay sensitive services include  Channel Sensitive Scheduling in both Time and Frequency Domain  Optimize the channel/user assignment for saving Tx power and minimizing interference.  Dynamic Forward Power Allocation in Frequency Domain  Reverse Power Control.  The PC rate for the 1x is 800Hz with no early termination, 400Hz with early termination.  Early Termination  It works well with imperfect power control and more channel fluctuation.

Delay Limited Capacity and CQI Feedback [The theory] For a single-user OFDM, the achievable delay-limited capacity in low SNR region strongly depends on the delay spread, not the path attenuations. In high SNR region, the roles are exchanged. From a multiuser scheduling perspective, one challenge is the balance between maintaining fairness for weak-channel users and maximizing throughput through strong-channel users.  The full DRC feedback for weak-channel users can help the AN with the efficient multiuser scheduling for delay sensitive services.  For the ATs with good channel reception, a single CQI feedback with necessary subband hopping is enough. In addition, with full DRC feedback for cell-edge ATs, it can help the AN not only schedule those ATs not only at a good balance between throughputs and fairness but also the interference management.

C/I Sensitive DRC Reporting DRC reporting is the mechanism to help AN with multiuser scheduling.  Typically a 4-bit DRC value is bi-orthogonally coded. DRC measurements can be obtained through both CDM time-domain pilots and OFDM frequency-domain pilots  The general C/I can be obtained from CDM pilots  The frequency selectivity can be observed through frequency-domain pilots DRC reporting can be optimized to reduce the feedback overhead for OFDMA.  Frequency selectivity gain is visible only when there is significant difference between subchannel gains.  When an AT sees the subchannel gains are pretty flat OR C/I ratios are pretty high, it may just report one DRC for all subchannels.  The packets for this AT will be transmitted with subband hopping or using all subbands for frequency diversity.  When an AT detects the variation of subbchannel gains is large AND C/I ratio is not high, it may report multiple DRCs or the DRC for the best subband instead.

Subband Hopping For the ATswith good C/I, subband DRC reporting is optional. If a high-DRC AT feedbacks only a single DRC for all subbands, AN has the following options  Option 1: The packets for high DRC will generally be transmitted through the whole MHz bandwidth or all subbands.  Option 2: The packets for high DRC can also be transmitted through one subband or multiple subbands.  The subband(s) allocated for the high DRC packet are not fixed. A predefined subband hopping is applied. If a high-DRC AT feedbacks multiple subband DRCs with significant variation, the AN may schedule the AT in good subband(s) with no subband hopping.

Cell-Edge Performance Improvements CDMA2000 1x is well-known to be interference limited, especially on cell edges: Pilot Interference, Overhead Channel Interference and Traffic Channel Interference. Multiple approaches are available for improving cell-edge performance including  Interference Management: power control and frequency reuse.  Subband OFDMA Frequency Reuse and Interference Management  Macro-diversity: cooperation between neighbor ANs.  Simple Broadcast Multicast Considerations for the AN Cooperation  Soft combining has the advantage of simple receiver design and the potential of 3 dB SNR gain.  Soft combining puts more scheduling constraints on the ANs.

Interference Management with SFR Interference management can be done in the subband level.  Interference avoidance is achievable in time domain (slots), frequency domain (subbands), space domain (sectors) and even through power allocations.  Finer granularity means higher achievable efficiency.  It help mobile do handoffs with less ping-pong. Subband frequency reuse can be done either through network planning or the full CQI report from the cell-edge ATs.

Cell Cooperation with Broadcast and Multicast Many emerging mobile services, e.g., alert service and positioning assistance service, require the same FL multicast to cover multiple sectors.  It is similar to the full-fledged BCMCS but only for small-sized data bursts, something like text message broadcast.  Its coverage is expected to be more flexible. For example, a couple of sectors or even one sector only. FL multicast in UHDR-DO is for efficiently delivering the same content to multiple users at the same time in one sector. It is desired to extend the FL multicast to cover multiple sectors with additional macro-diversity gains.

simple Broadcast Multicast Services Physical Layer:  More than one sectors can transmit the same signal streams with the same content at the same time and frequency.  For alleviating the scheduling constraints, the multicast signal stream can be transmitted through MUP and layered transmission.  The pilots for separately the channel estimation of each layer are superimposed together with special rotations  One MUP MAC ID is especially reserved with multicast capability. MAC Layer: AT assigned an unicast MAC ID and multicast MAC ID from each sector in its active set. Connection Layer  AN may assign Multicast MAC address via TCA

Pilots for Simple BCMCS For the soft combining simple BCMCS data from different sectors, the sector-specific overheads transmission are separated from the data transmission. The data can be transmitted from a separated layer, which has a layer- specific pilots.