September 2015 doc IEEE 802 11 150602 r

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 HE-LTF Sequence for UL MU-MIMO Date: 2015 -09 -13 Authors: Name Affiliation Address Phone Qinghua Li quinghua. li@intel. com Xiaogang Chen Robert Stacey Po-Kai Huang Email Intel Chitto Ghosh 2111 NE 25 th Ave, Hillsboro OR 97124, USA xiaogang. c. chen@intel. com +1 -408 -765 -9698 robert. stacey@intel. com po-kai. huang@intel. com chittabrata. ghosh@intel. com Rongzhen Yang rongzhen. yang@intel. com Hongyuan Zhang hongyuan@marvell. com Yakun Sun yakunsun@marvell. com Lei Wang Liwen Chu Jinjing Jiang Marvell 5488 Marvell Lane, Santa Clara, CA, 95054 Leileiw@marvell. com +408 -222 -2500 liwenchu@marvell. com jinjing@marvell. com Yan Zhang yzhang@marvell. com Rui Cao ruicao@marvell. com Submission Slide 1 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Authors (continued) Name Affiliation Address Phone Email Jie Huang jiehuang@marvell. com Sudhir Srinivasa sudhirs@marvell. com Saga Tamhane Mao Yu Marvell (Cont’d) 5488 Marvell Lane, Santa Clara, CA, 95054 408 -222 -2500 sagar@marvell. com my@marvel. . com Edward Au edwardau@marvell. com Hui-Ling Lou hlou@marvell. com Ron Porat rporat@broadcom. com Matthew Fischer mfischer@broadcom. com 170 W Tasman Dr, San Jose, CA 95134 brianh@cisco. com pmonajem@cisco. com Sriram Venkateswaran Broadcom Tu Nguyen Vinko Erceg Brian Hart Pooya Monajemi Submission Cisco Systems Slide 2 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Authors (continued) Name Phone Email Wookbong Lee wookbong. lee@lge. com Kiseon Ryu kiseon. ryu@lge. com Jinyoung Chun jiny. chun@lge. com Jinsoo Choi js. choi@lge. com jeongki. kim@lge. com giwon. park@lge. com Dongguk Lim dongguk. lim@lge. com Suhwook Kim suhwook. kim@lge. com Eunsung Park esung. park@lge. com Han. Gyu Cho hg. cho@lge. com thomas. derham@orange. com Jeongki Kim Giwon Park Thomas Derham Submission Affiliation LG Electronics Orange Address 19, Yangjae-daero 11 gil, Seocho-gu, Seoul 137130, Korea Slide 3 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Authors (continued) Name Affiliation Phone Email +44 1223 434633 f. tong@samsung. com +82 -31 -279 -9028 hyunjeong. kang@samsung. com (972) 761 7437 k. josiam@samsung. com +44 1223 434600 m. rison@samsung. com (972) 761 7470 rakesh. taori@samsung. com +82 -10 -8864 -1751 s 29. chang@samsung. com Yasushi Takatori takatori. yasushi@lab. ntt. co. jp Yasuhiko Inoue inoue. yasuhiko@lab. ntt. co. jp asai. yusuke@lab. ntt. co. jp Koichi Ishihara ishihara. koichi@lab. ntt. co. jp Akira Kishida kishida. akira@lab. ntt. co. jp yamadaakira@nttdocomo. com Fei Tong Hyunjeong Kaushik Josiam Mark Rison Samsung Rakesh Taori Sanghyun Chang Yusuke Asai NTT Haralabos Papadopoulos Submission Innovation Park, Cambridge CB 4 0 DS (U. K. ) Maetan 3 -dong; Yongtong-Gu Suwon; South Korea 1301, E. Lookout Dr, Richardson TX 75070 Innovation Park, Cambridge CB 4 0 DS (U. K. ) 1301, E. Lookout Dr, Richardson TX 75070 Maetan 3 -dong; Yongtong-Gu Suwon; South Korea 1 -1 Hikari-no-oka, Yokosuka, Kanagawa 239 -0847 Japan 3 -6, Hikarinooka, Yokosuka-shi, Kanagawa, 239 -8536, Japan Akira Yamada Fujio Watanabe Address NTT DOCOMO 3240 Hillview Ave, Palo Alto, CA 94304 Slide 4 watanabe@docomoinnovations. com hpapadopoulos@docomoinnovat ions. com Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Authors (continued) Name Affiliation Address Phone Email Phillip Barber The Lone Star State, TX pbarber@broadbandmobilete ch. com Peter Loc peterloc@iwirelesstech. com Le Liu F 1 -17, Huawei Base, Bantian, Shenzhen 5 B-N 8, No. 2222 Xinjinqiao Road, Pudong, Shanghai 10180 Telesis Court, Suite 365, San Diego, CA 92121 NA 303 Terry Fox, Suite 400 Kanata, Ottawa, Canada F 1 -17, Huawei Base, Bantian, Shenzhen 10180 Telesis Court, Suite 365, San Diego, CA 92121 NA F 1 -17, Huawei Base, Bantian, SHenzhen 303 Terry Fox, Suite 400 Kanata, Ottawa, Canada 5 B-N 8, No. 2222 Xinjinqiao Road, Pudong, Shanghai +86 -18601656691 liule@huawei. com jun. l@huawei. com +86 -18665891036 Roy. luoyi@huawei. com linyingpei@huawei. com pangjiyong@huawei. com zhigang. rong@huawei. com Rob. Sun@huawei. com david. yangxun@huawei. com yangyunsong@huawei. com +86 -18565826350 Lanzhou 1@huawei. com Junghoon. Suh@huawei. com +86 -18601656691 zhangjiayin@huawei. com Jun Luo Yingpei Lin Jiyong Pang Zhigang Rob Sun David X. Yang Yunsong Yang Zhou Lan Junghoon Suh Jiayin Zhang Submission Huawei Slide 5 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Authors (continued) Name Affiliation Address Qualcomm Straatweg 66 -S Breukelen, 3621 BR Netherlands 5775 Morehouse Dr. San Diego, CA, USA 1700 Technology Drive San Jose, CA 95110, USA 5775 Morehouse Dr. San Diego, CA, USA Straatweg 66 -S Breukelen, 3621 BR Netherlands 1700 Technology Drive San Jose, CA 95110, USA 5775 Morehouse Dr. San Diego, CA, USA 1700 Technology Drive San Jose, CA 95110, USA Albert Van Zelst Alfred Asterjadhi Bin Tian Carlos Aldana George Cherian Gwendolyn Barriac Hemanth Sampath Menzo Wentink Richard Van Nee Rolf De Vegt Sameer Vermani Simone Merlin Tevfik Yucek VK Jones Youhan Kim Submission Slide 6 Phone Email allert@qti. qualcomm. com aasterja@qti. qualcomm. com btian@qti. qualcomm. com caldana@qca. qualcomm. com gcherian@qti. qualcomm. com gbarriac@qti. qualcomm. com hsampath@qti. qualcomm. com mwentink@qti. qualcomm. com rvannee@qti. qualcomm. com rolfv@qca. qualcomm. com svverman@qti. qualcomm. com smerlin@qti. qualcomm. com tyucek@qca. qualcomm. com vkjones@qca. qualcomm. com youhank@qca. qualcomm. com Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Authors (continued) Name Affiliation Address Phone Email No. 1 Dusing 1 st Road, Hsinchu, Taiwan +886 -3 -567 -0766 james. yee@mediatek. com alan. jauh@mediatek. com Chingwa Hu chinghwa. yu@mediatek. co m Frank Hsu frank. hsu@mediatek. com James Yee Alan Jauh Mediatek 2860 Junction Ave, San +1 -408 -526 -1899 Jose, CA 95134, USA Thomas Pare Chao. Chun Wang James Wang Jianhan Liu Mediatek USA thomas. pare@mediatek. com chaochun. wang@mediatek. c om james. wang@mediatek. com Jianhan. Liu@mediatek. com Tianyu Wu tianyu. wu@mediatek. com Russell Huang russell. huang@mediatek. co m Eric Wong +1 -408 -9745967 ericwong@apple. com Chris Hartman Joonsuk Kim joonsuk@apple. com Guoqing Li +1 -408 -974 -9164 guoqing_li@apple. com Aon Mujtaba Submission Apple Cupertino, CA Slide 7 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Authors (continued) Name Affiliation Address Phone Weimin Xing Kaiying Lv Email Xing. weimin@zte. com. c n lv. kaiying@zte. com. cn ZTE Corp. Ke Yao. ke@zte. com. cn Bo Sun. bo 1@zte. com. cn Yonggang Fang Submission ZTE TX yfang@ztetx. com Slide 8 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Background • P matrix coded HE-LTF was adopted in last meeting [1] – Maximize legacy reuse • Adding details, we propose HE-LTF sequences for uplink multiuser MIMO Submission Slide 9 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Problem Statement • In uplink multiuser MIMO, different UL users have different carrier frequency offsets • AP may want to estimate the CFOs for demodulating data and mitigating multiuser interference • For the CFO estimation, per-stream phase offsets at different LTF symbol instants need to be obtained Submission Slide 10 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Proposed Solution • Assign orthogonal LTF sequences to different streams within the UL MU-MIMO burst – Exploit frequency domain correlation – Per-stream channel responses can be estimated for each LTF symbol – CFO can be estimated by checking the phase difference between the channel estimates obtained at different LTF symbols • Additional benefit — No need to insert pilot tones in LTF symbols Submission Slide 11 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Generating LTF sequences • Generated from P matrix – Scramble a common sequence by different rows of P matrix • Piecewise orthogonal – Sub-sequences with any K (e. g. 4) contiguous entries are orthogonal Submission Slide 12 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Cyclic Orthogonality • Orthogonal sequences of any length can be generated by exploiting cyclic orthogonality among P matrix rows – E. g. 2 users with 26 tones and K=4 [1 -1] X User 1 L 2 X L 3 L 4 … L 21 L 22 L 1 L 23 L 24 L 3 L 4 … L 21 L 22 L 25 L 26 [1 1] X X User 2 X X L 23 L 24 L 25 L 26 orthogonal Submission Slide 13 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Orthogonal Tone Blocks • By exploiting cyclic orthogonality, we have many orthogonal tone blocks generating data samples for CFO estimation User 1 S 1(1 ) S 1(2 ) S 1(3 ) S 1(4 ) S 1(5 ) S 1(6 ) S 1(7 ) S 1(8 ) S 1(9 ) … User 2 S 2(1 ) S 2(2 ) S 2(3 ) S 2(4 ) S 2(5 ) S 2(6 ) S 2(7 ) S 2(8 ) S 2(9 ) … Orthogonal tone block 1 Submission Orthogonal … tone block 2 Slide 14 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 LTF symbols of stream k Stream index Sequence common to all streams Tone index LTF symbol index Subcarrier 1 Subcarrier 2 Time LTF symbol 1 Submission LTF symbol 2 Slide 15 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 LTF symbols of multiple streams • Orthogonal sequences are applied to different streams on each tone block Orthogonal sequences Submission Slide 16 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 CFO Estimation • Channel response remains roughly constant over each tone block • Phase response is estimated from each tone block • CFO is estimated by averaging the phase rotation rate over tone blocks and Rx antennas Orthogonal sequences Submission Slide 17 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 One P matrix for all • Since the 8× 8 P matrix consists of orthogonal 2× 2 and 4× 4 sub-matrixes, we can use the rows of 8× 8 P matrix to define LTF sequences for up to 8 streams Submission Slide 18 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Simulation Assumptions • • • Uplink MU-MIMO 8 Rx antennas at AP, 4/6 STAs each sending 1 stream MCS 7/MCS 4; 20 MHz bandwidth; Ch. DNLo. S/UMi. NLo. S CFO error is modeled as +CFO/-CFO with fixed value Timing offset is uniformly distributed over [0, Toff ns] for each STA CSD value follows 11 ac & 11 ax larger CSD(TBD) Per STA pilot tracking is enabled CFO is estimated and compensated for the proposed new LTF sequence Channel smoothing is not applied 4 x/2 x (3. 2 us/1. 6 us GI) LTF is used Submission Slide 19 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 CFO Tolerance Tolerate +/- 400 Hz CFO within negligible degradation to ideal and >3 d. B improvement over legacy Submission Slide 20 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Timing Offset Tolerance 3 d. B Within 1 d. B Tolerate 1 μs timing offset at 10% PER with sub-d. B degradation to ideal and 3 d. B improvement over legacy Submission Slide 21 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Robust to Frequency Selectivity Work fine in outdoor channels Submission Slide 22 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 With per-stream CSD Work fine with CSD Submission Slide 23 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 2 x LTF 10 Ch. D 4 STA 2 x 0 Freqoff 0 Hz/ 11 ac LTF Freqoff 400 Hz/ new LTF Freqoff 400 Hz/ 11 ac LTF -1 PER 10 2 d. B 10 10 -2 -3 20 22 24 26 SNR(d. B) 28 30 32 Work fine with 2 x LTFs Submission Slide 24 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 UL transmission with beamforming • 20 MHz channel • STA: 2 Tx ant. with ideal beamforming • AP: 8 Rx ant. • 4 STAs 0. 3 d. B • • Rank inverse in BF may cause phase discontinuity, which will break the orthogonality in frequency domain. The observation is rank inverse does not occur frequently. Even it happens, only limited samples are affected. Submission Slide 25 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 UL transmission with power offset • • • 0. 2 d. B • • STA: 1 Tx ant. AP: 8 Rx ant. 4 STAs received with 0 d. B power 1 STA received with 10 d. B power 1 STA received with 6 d. B power 0. 2 d. B Stronger stream may leak power to the weaker stream due to non-ideal orthogonality; The CFO estimation is not impacted too much if the power leakage is within moderate range. – We see some obvious impact for power offset > 10 d. B Submission Slide 26 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 PAPR Issue • Use fixed point simulation to evaluate if the dynamic range increase in HELTF impacts the overall performance (10/6 bits quantization is considered); • The PAPR increase in the masked LTF has marginal impact to the overall performance. – PAPR in the data part is the bottleneck. Submission Slide 27 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Summary • UL MU-MIMO CFO estimation is enabled by assigning orthogonal LTF sequences to different streams – Optimal performance – Maximum reuse of legacy design – Low complexity • Propose to use the rows of 8× 8 P matrix as the masking sequences for generating the orthogonal HE-LTF sequences for UL MU-MIMO Submission Slide 28 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Reference [1] “Specification Framework for TGax, ” doc. : IEEE 802. 11 -15/0132 r 4, Section 3. 2, March 2015 Submission Slide 29 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Straw Poll 1 • Do you agree to add to TGax Specification Framework Document? – The HE-LTF sequences for UL MU-MIMO shall be generated as follows. For each stream, a common sequence shall be masked repeatedly in a piece-wise manner by a distinct row of an 8 x 8 orthogonal matrix. When the length of the LTF sequence is not divisible by 8, the last M elements of the LTF sequence (M being the remainder after the division of LTF length by 8) shall be masked by the first M elements of the orthogonal matrix row. – Yes – No – Abstain Submission Slide 30 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Straw Poll 2 • Do you agree to add to TGax Specification Framework Document? – The orthogonal matrix used to mask the HE-LTF sequence in SP 1 is the 8 x 8 Pmatrix used in 11 ac. Submission Slide 31 Qinghua Li, Xiaogang Chen, et al.

September, 2015 doc. : IEEE 802. 11 -15/0602 r 6 Backup Submission Slide 32 Qinghua Li, Xiaogang Chen, et al.

September, 2015 Submission doc. : IEEE 802. 11 -15/0602 r 6 Slide 33 Qinghua Li, Xiaogang Chen, et al.