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NDP sounding

NDP sounding. Date: 2012-05-14. Authors:. Introduction. IEEE 802.11ac Null Data Packet (NDP) sounding SU: Only Immediate-SIFS feedback (after NDP) is allowed, not allow delayed or aggregated feedbacks. MU: Feedback happens SIFS after NDP, or SIFS after polling frames.

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NDP sounding

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  1. NDP sounding Date: 2012-05-14 Authors: YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

  2. YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

  3. YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

  4. Introduction • IEEE 802.11ac Null Data Packet (NDP) sounding • SU: Only Immediate-SIFS feedback (after NDP) is allowed, not allow delayed or aggregated feedbacks. • MU: Feedback happens SIFS after NDP, or SIFS after polling frames. • IEEE 802.11ac NDP sounding can be reused for 2>= MHz beam-forming in IEEE 802.11ah • But, NDP sounding frame format (>=2MHz modes) is not defined yet YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

  5. 11ac NDP sounding frame • IEEE 802.11ac has a common frame structure for SU-MIMO, MU-MIMO and NDP • Variable SIG contents in an 11ac NDP frame • The number of space-time streams (NSTS) • Channel bandwidth (20/40/80/160MHz) … L-STF L-LTF L-SIG VHT-SIG-A (Symbol 1) VHT-SIG-A (Symbol 2) VHT-STF VHT-LTF1 VHT-LTFN VHT-SIG-B YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

  6. Proposed 11ah NDP sounding frame for >= 2MHz Modes • Current 11ah spec framework supports two different frames for >= 2MH modes, short frame and long frame • We have two options for 11ah NDP sounding frame • Option 1) Short frame • It is the same with 2 MHz short frame format defined in 11ah spec framework R.3.2.1.1.A • Option 2) Long frame • It is the same with 2 MHz long frame format defined in 11ah spec framework R.3.2.1.1.B … STF LTF1 SIG (2 symbols) LTF2 LTF_N … STF LTF1 SIGA (2 symbols) D-STF D-LTF1 D-LTF_N SIG-B YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

  7. Proposed 11ah NDP sounding frame for >= 2MHz Modes • Option 1 (short frame) is more reasonable for IEEE 802.11ah NDP sounding frame • Pros : Less overhead • Cons : Less time budget, because there is no additional SIG after LTFs • Immediate feedback time budget is 320us and it may be enough to compute V and prepare BF • The immediate feedback time budget of 11ac is about 50us NDP Immediate FB frame SIFS AH-STF AH-LTF AH-SIG …. Compute V Compress V and Prepare FB SIFS (80us) + PLCP Header (40*6us) = 320 us YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

  8. Proposed 11ah NDP sounding frame for >= 2MHz Modes • Proposed SIG field in NDP sounding frame includes following bits • MCS : set to 0 • MCS values 0 – 9 are reserved for normal PPDU • MCS values 10 – 15 are reserved for NDP PPDU • Length/Duration : set to 0 • BW : set to the same value as the TXVECTOR parameter CH_BANDWIDTH in the preceding VHT NDP Announcement frame • Nsts : indicates two or more space-time streams YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

  9. Proposed 11ah NDP short MAC frame for >= 2MHz Modes • 1MHz Short MAC frames is of the same format as the current 1MHz preamble • But, all NDP short MAC frame sent in >=2MHz also has two options, short frame and long frame • For making a consistency with NDP sounding frame, it makes sense to use a short frame format for Short-ACK, Short-CTS, and all future NDP short MAC frames • Meaning that SIG field is always modulated by {QBPSK, QBPSK} STF LTF1 SIG Remaining LTFs YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

  10. Summary • IEEE 802.11ac NDP sounding can be reused for 2/4/8/16MHz beam-forming in IEEE 802.11ah • We propose Option 1 (in slide 6) as 11ah NDP sounding format • We propose SIG field of 11ah NDP sounding format in slide 8 • Also, we propose that all NDP short MAC frames in >=2MHz use the short frame format. YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

  11. Straw Poll 1 • Do you support the following 11ah NDP sounding format for >= 2MHz modes? … STF LTF1 SIG (2 symbols) LTF2 LTF_N • It is the same with 2 MHz PHY short frame format defined in 11ah spec framework R.3.2.1.1.A YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

  12. Straw Poll 2 • Do you support including the following fields described in slide 8 in the SIG field of 11ah NDP sounding format for >= 2MHz modes ? • MCS : set to 0 • Length/Duration : set to 0 • BW : set to the same value as the TXVECTOR parameter CH_BANDWIDTH in the preceding VHT NDP Announcement frame • Nsts : indicates two or more space-time streams YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

  13. Straw Poll 3 • Do you support that all NDP short MAC frames sent in >=2MHz use the short frame? • Include Short-ACK, Short-CTS, and all future NDP short MAC frames YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

  14. References [1] Draft P802.11ac_D2.0 [2] Minyoung Park, “Proposed Specification Framework for TGah”, IEEE 802.11-11/1137r6 [3] Yong Liu, “Short ACK”, IEEE 802.11-12/324r2 YonghoSeok (LG Electronics), HongyuanZhang (Marvell)

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