doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 1 Comment Resolution on TX Beamforming CSI/Steering Feedback Quantization Bitwidth N b Notice: This document has been prepared to assist IEEE It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE Working Group. If you have questions, contact the IEEE Patent Committee Administrator at. Date:

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 2 CID 344 Since the antenna configuration is constraint to 4x4, we don't need N_b to be as high as 8 bits. Remove 8, and leave the max to be 6 bits. CID 857 Currently the coefficient size Nb in MIMO control field in Figure n21 has 4 options {4,5,6,8}. Would be good to allow more resolution choices for steering matrix precision (for example Nb = 3 or Nb = 7). Use additional reserved bit in MIMO control field so that Nb field is 3 bits long. Then Nb = number represented by 3 bits + 1. Then shift "Codebook information" and "remaining matrix segment" subfields to the right by 1 bit. Also the Nb values in Clause and at page 286 need to be modified.

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 3 Overview Based on our simulations for different Nb: –For CSI feedback, Nb=4 performs optimal or near optimal (in terms of goodput) in most of the cases. –For non-compressed steering feedback, Nb = 3 and 4 perform similarly (in terms of goodput) in most of the cases; and Nb = 2 may be preferable (in terms of goodput) for some scenarios. –For both CSI and non-compressed steering feedback, Nb = 8 and Nb=6 result in similar PER performance. Nb=8 performs slightly better than Nb=4 in PER. We suggest to differentiate the Nb values for CSI feedback and non-compressed steering feedback, given that their performance changes on different feedback bitwidth are NOT similar. Therefore we suggest to keep current set of Nb values for CSI feedback. We suggest to modify the set of possible Nb values for non-compressed steering feedback to more appropriately reflect actual performances. This will also provide more flexibility towards balancing the feedback overhead with performances over different configurations, eg. SNR range of a location, Doppler effects, different MCS, steering calculation approaches, etc. –This requires the maximum possible dynamic range of Nb values Nb = 8 may be desirable in some applications requiring high resolution feedback (e.g. Calibration exchange for implicit TxBF), therefore it should be kept as one option.

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 4 Proposed Solutions CID 344: reject (refer to r0) CID 857: counter (refer to r0) Summary of the resolution (refer to r0 for details) –In D2.02, , table 24a, keep the current 4 possible Nb values for CSI feedback, and reinterpret the 4 possible Nb values to be {4,2,6,8} for non-compressed steering feedback. –Update Nb values in correspondingly.

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 5 Simulation Settings Channel D/B NLOS, MCSs with Nss=1 and 2 Explicit TxBF with CSI Feedback or with Non-compressed Steering, Ng=1 (no tone grouping) RF Impairments added PERs are plotted PHY layer goodput is plotted: –PHY preamble and CSI feedback treated as overhead –Lowest rate (MCS 0) on CSI feedback—assume error-free –Burst transmission (SIFS interval) assumed for steered packets –Fast fading case (fd=6 Hz) : TxBF sounding interval is set in the range where the channel Doppler does not affect PER significantly.

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 6 I. CSI Feedback

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 7 PER v.s. SNR for MCS 6, Nrx=1, Ntx=3, Channel D NLOS SNR (dB) PER

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 8 Goodput v.s. SNR for MCS 6, Nrx=1, Ntx=3, 5ms sounding interval * Nb=3 wins out for most SNRs, * Nb=2 preferred at high SNR.

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 9 Goodput v.s. SNR for MCS 6, Nrx=1, Ntx=3, 10ms sounding interval * Nb=3 wins out at most SNRs, * Nb=2 performs well at high SNR. * No significant differences between 5 and 10 ms sounding intervals

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 10 PER v.s. SNR for MCS 9, Nrx=2, Ntx=3, Channel D NLOS

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 11 Goodput v.s. SNR for MCS 9, Nrx=2, Ntx=3, Channel D NLOS, 10 ms sounding interval * Nb=4 wins out at most SNRs, * Nb=3 preferred at high SNR.

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 12 PER v.s. SNR for MCS 12, Nrx=2, Ntx=3, Channel D NLOS

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 13 Goodput v.s. SNR for MCS 12, Nrx=2, Ntx=3, Channel D NLOS, 10 ms sounding interval * Nb=4 wins out for most SNRs,

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 14 PER v.s. SNR for MCS 15, Nrx=2, Ntx=3, Channel B NLOS

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 15 Goodput v.s. SNR for MCS 15, Nrx=2, Ntx=3, Channel B NLOS, 10 ms sounding interval * Nb=4 is favorable

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 16 II. Non-compressed Steering Feedback

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 17 PER v.s. SNR for MCS 1, Nrx=1, Ntx=3, Channel D NLOS

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 18 Goodput v.s. SNR for MCS 1, Nrx=1, Ntx=3, Channel D NLOS, 10 ms sounding interval * Nb=2~4 perform similar, and are favorable through all SNR

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 19 PER v.s. SNR for MCS 6, Nrx=1, Ntx=3, Channel D NLOS

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 20 Goodput v.s. SNR for MCS 6, Nrx=1, Ntx=3, Channel D NLOS, 10 ms sounding interval * Nb=2, 3, 4 performs similar and are favorable through all SNR

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 21 PER v.s. SNR for MCS 14, Nrx=2, Ntx=3, Channel D NLOS

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 22 Goodput v.s. SNR for MCS 14, Nrx=2, Ntx=3, Channel D NLOS, 10 ms sounding interval * Nb=3 desirable until intermediate SNR * Nb=2 desirable at high SNR

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 23 PER v.s. SNR for MCS 23, Nrx=4, Ntx=4, Channel D NLOS

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 24 Goodput v.s. SNR for MCS 23, Nrx=4, Ntx=4, Channel D NLOS, 10 ms sounding interval * Nb=3 desirable until intermediate SNR * Nb=2 desirable at high SNR

doc.: IEEE /0612r0 Submission May 2007 H. Zhang., et al.Slide 25 Conclusions For feedback limited cases (i.e., fast-fading), smaller Nb (4, 3, or 2) may achieve higher goodput than larger Nb. Non-compressed steering FB is less sensitive to reduced Nb values, Nb=3,2 could be even more desirable in this case. Nb = 8 may perform only slightly better than Nb=4 on PER. Different range of Nb values (2~8) will give more design flexibility for non-compressed steering feedback (w.r.t. channel Doppler, SNR, MCS, the steering calculation approaches, etc). When optimal link adaptation is involved, goodput results could be different, but smaller Nb values will be still desirable in some cases (e.g. non-compressed steering feedback with one data stream)