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11ah Preamble for 2MHz and Beyond

11ah Preamble for 2MHz and Beyond. Authors:. Date: 2011-11-07. Abstract. This presentation proposes the preamble format for 11ah 2MHz, and wider BW packets, including 4MHz, 8MHz and 16MHz.

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11ah Preamble for 2MHz and Beyond

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  1. 11ah Preamble for 2MHz and Beyond Authors: Date: 2011-11-07 Hongyuan Zhang, et. Al.

  2. Abstract This presentation proposes the preamble format for 11ah 2MHz, and wider BW packets, including 4MHz, 8MHz and 16MHz. Hongyuan Zhang, et. Al.

  3. 11ac and 11n preambles apply a mixed-mode preamble, which is composed by a legacy portion for legacy device to decode the signal field, and a (V)HT portion. • Legacy portion and (V)HT portion have AGC fields separately. • 11ac also relies on MM preamble for transmitting MU packets. • 11n also defines a green field preamble, in which only HT portion is present, and preamble duration is shorter • Extra protection is required for GF transmissions. Background HT-MM: Legacy portion HT portion L-STF L-LTF L-SIG HT-SIG HT-STF HTLTF1 HTLTF2 HTLTF3 HTLTF4 HT-DATA 2 symb 2 symb 1 symb 2 symb 1 symb 1 symb … HT-GF: HT-STF HTLTF1 HT-SIG HTLTF2 HTLTF3 HTLTF4 HT-DATA 2 symb 2 symb 2 symb 1 symb 1 symb … Hongyuan Zhang, et. Al.

  4. 2/4/8/16MHz signals are basically downclocked versions of 11ac 20/40/80/160MHz. • 11ah is a “green field” system, therefore a green field type of preamble is preferred, at least for regular single user (SU) packet. • Downlink MU-MIMO may be an optional feature for 11ah, its benefit may be limited to WiFi offloading use cases—therefore MU preamble should not burden regular SU frame format • Different from 11ac, in which a common preamble format was defined for both MU and SU • Therefore we propose a different MU “mixed mode” frame format for >=2MHz, which is similar to 11ac MU packet format. Overview: 802.11ah Preamble for >=2MHz Hongyuan Zhang, et. Al.

  5. I. SU Preamble for >=2MHz • The general structure for SU packet is similar to 11n green field preamble, as below. • Each field is explained in subsequent slides. QBPSK … STF LTF1 SIG LTF2 LTF_NLTF DATA (2 symbols) (2 symbols ) (2 symbols) (1 symbol each) DGI LTS LTS Hongyuan Zhang, et. Al.

  6. In data tones of LTF, the mapping from NSTS space-time streams to NLTF LTFs is the same as in 11n green field preamble, with the P matrix. LTF Fields Hongyuan Zhang, et. Al.

  7. Use the same tone design as in 11n, i.e. in each 2MHz, STF occupies 12 non-zero tones in {±4 ±8 ±12 ±16 ±20 ±24}. As in 11n greenfield, the same preamble expression is for both open-loop and SU-Beamformed packets, therefore STF field is beamformed in a SU beamformedpacket. None-zero tones are mapped to space-time streams using the first column of P matrix, the same way as in 11n GF preamble. STF Field Hongyuan Zhang, et. Al.

  8. 2 symbols, each modulated using Q-BPSK, same as in 11n green field preamble. • 52 data tones, modulated using 11n/11ac MCS0. • Note that 11n HTSIG uses 48 data tones. • Data tones are mapped to multiple space-time streams using the first column of P matrix—the same as in 11n GF preamble. • SIG field subfield definitions are TBD • Specific for 11ah, not necessarily the same as 11n/11ac. SIG Field Hongyuan Zhang, et. Al.

  9. Propose MU packets using a “mixed-mode” format II. MU Preamble for >=2MHz “Omni” Portion MU Portion … STF LTF1 SIGA MU-STF MU-LTF1 MU-LTF_NLTF SIGB DATA (2 symbols) (2 symbols as 11n GF) (2 symbols) (1 symbol) (1 symbol each) DGI LTS LTS Hongyuan Zhang, et. Al.

  10. LTF1 and SIG field both have 52 data tones. • Different from the legacy portion of 11n MM preamble and 11ac preamble. • STF/LTF1/SIG fields applies single stream in each subcarrier (without the 1st column P matrix mapping as seen in SU preamble), similar to the legacy portion of 11n MM preamble and 11ac preamble. • SIG field subfield definition is different from SU, and the two symbols in SIG field are modulated using QBPSK and BPSK respectively • Refer to later “auto-detection” slide. Omni Portion Hongyuan Zhang, et. Al.

  11. MU-STF is the same as (downclocked) 11ac VHT-STF. • Modulation flows of MU-STF, MU-LTFs, and SIGB are the same as 11ac MU packets. • i.e. all streams for all users are trained by MU-LTFs. • Up to 4 space-time stream across all users (refer to [2]). MU Portion Hongyuan Zhang, et. Al.

  12. For >=2MHz SU and MU packets, the 1st SIG symbol is always QBPSK • Used for autodetection between 1MHz and 2MHz preamble—refer to [1]. • The 2nd SIG symbol is used for autodetection between SU and MU packets. Auto-Detections QBPSK QBPSK LTF1 GI SIG1 GI SIG2 64FFT SIG for SU: QBPSK BPSK LTF1 GI SIGA1 GI SIGA2 64FFT SIG for MU: Refer to [1] for 1MHz and 2MHz autodetection 1MHz LTF1: (refer to [1]) DGI LTS LTS GI LTS GI LTS Hongyuan Zhang, et. Al.

  13. For 4MHz, 8MHz, and 16MHz packets, the STF/LTF/SIG field designs are similar to 11ac 40/80/160MHz. • STF/SIG fields are repeated and phase rotated (same as in 11ac) over each 2MHz subband. • LTF signs in the tones of each 2MHz subband, when overlapping with the tones with a stand-alone 2MHz LTF, have the same values as the corresponding signs in 2MHz LTF. Wider BW Hongyuan Zhang, et. Al.

  14. Do you agree with the “green field” type preamble structure for >=2MHz SU packets, as shown in slide 5? Straw Poll - 1 Hongyuan Zhang, et. Al.

  15. Do you agree with the MU preamble structure for >=2MHz packets, as shown in slide 9? Straw Poll - 2 Hongyuan Zhang, et. Al.

  16. Do you agree with the SU/MU autodetection mechanism, as shown in slide 12? Straw Poll - 3 Hongyuan Zhang, et. Al.

  17. [1] 11-11-1482-00-00ah-preamble-format-for-1-MHz [2] 11-11-1275-01-00ah-spatial-stream-support References Hongyuan Zhang, et. Al.

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