1. doc.: IEEE 802.11-07/0612r3 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 802.11. 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 802.11. 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 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at.http:// ieee802.org/guides/bylaws/sb-bylaws.pdfstuartk@ok-brit.compatcom@ieee.org Date: 2007-07-16

2. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 2 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 20.3.11.2.1 and 20.3.11.2.2 at page 286 need to be modified.

3. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 3 Overview Based on our simulations for different Nb: –For non-compressed steering feedback, Nb = 2 bits may be preferable (in terms of goodput) for some scenarios. –In these cases, compared with Nb=4,5,8, Nb=2 achieves almost the same packet error rate while reducing the amount of feedback by a factor greater than 2—translates to throughput improvement. We suggest to interpret the Nb values in MIMO control field differently for CSI feedback and non-compressed steering feedback –Reinterpret the set of possible Nb values for non-compressed steering feedback in the “Coefficient Size” subfield of MIMO control field, to more appropriately reflect actual performance.

4. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 4 Proposed Solutions CID 857: counter (refer to 11-07-0613r2 for details) Summary of the resolution –In D2.02, 7.3.1.29, table n14, keep the current 4 possible Nb values for CSI feedback, and reinterpret the Nb=5 to Nb=2 for non-compressed steering feedback. –Update Nb values in 20.3.11.2.2 correspondingly. Coefficient Size Indicates the number of bits in the representation of the real and imaginary parts of of each element in the matrix: For CSI feedback: Set 0 for Nb=4 Set 1 for Nb=5 Set 2 for Nb=6 Set 3 for Nb=8 For Non-compressed beamforming matrix feedback: Set 0 for Nb=2 Set 1 for Nb=4 Set 2 for Nb=6 Set 3 for Nb=8

5. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 5 Simulation Settings Channel DNLOS, MCSs with Nss=1 4 TX, 1 RX Antenna, fast fading—e.g. mobile outdoor Explicit TxBF with Non-compressed Steering feedback, Ng=1 (no tone grouping) RF Impairments & channel estimation error PER vs. SNR is plotted PHY layer goodput is plotted: –PHY preamble and non-compressed steering feedback treated as overhead –Explicit feedback with lowest rate (MCS 0) — 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.

6. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 6 PER v.s. SNR for MCS 7, Nrx=1, Ntx=4, Channel D NLOS

7. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 7 Goodput v.s. SNR for MCS7, Nrx=1, Ntx=4, Channel D NLOS, 5 ms sounding interval

8. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 8 Goodput MCS7 1x4 Cont’d: Zooming In >2 dB gain over Nb=4 ~2.5 dB gain over Nb=5

9. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 9 PER v.s. SNR for MCS 4, Nrx=1, Ntx=4, Channel D NLOS

10. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 10 Goodput v.s. SNR for MCS 4, Nrx=1, Ntx=4, Channel D NLOS, 5 ms sounding interval

11. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 11 Goodput MCS4 1x4 Cont’d: Zooming In 1.5 dB gain over Nb=4 ~2 dB gain over Nb=5

12. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 12 PER v.s. SNR for MCS0, Nrx=1, Ntx=4, Channel D NLOS

13. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 13 Goodput v.s. SNR for MCS0, Nrx=1, Ntx=4, Channel D NLOS, 5 ms sounding interval

14. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 14 Goodput MCS0 1x4 Cont’d: Zooming In 1.3 dB gain over Nb=4 >1.5 dB gain over Nb=5

15. doc.: IEEE 802.11-07/0612r3 Submission May 2007 H. Zhang., et al.Slide 15 Conclusions For non-compressed feedback, Nb=2 outperforms Nb=5 in goodput for the considered cases. Choosing between Nb = 4,5,6 does not offer significant advantages – in terms of PER vs. SNR or goodput. Given that Nb=4, 6 already exist, Nb=5 will rarely be used. A larger span of possible Nb values (2,4,6,8) gives more design flexibility for non-compressed steering feedback.