Cyclic Shift Delay (csd) was introduced since 802. 11n


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Date: 2016-05-16

  • Date: 2016-05-16




















Cyclic Shift Delay (CSD) was introduced since 802.11n

  • Cyclic Shift Delay (CSD) was introduced since 802.11n

    • De-couple the same STF signals transmitted on multiple antennas /streams for better Rx AGC setting
    • Provide diversity in data field and pilot tracking
  • In this presentation we propose the CSD design for 11ax



Following 11ac design rational

  • Following 11ac design rational

    • Per stream CSD
      • Mandatory for HE modulated fields
      • Also applicable to pre-HE modulated fields when beam_change=0 (HE SU only)
    • Per antenna CSD
      • Mandatory for pre-HE modulated fields when beam_change=1
      • Not specified for the HE portion and the pre-HE portion when beam_change=0. Can be applied as part of Q matrix


Propose to reuse the 11ac per stream CSD values for all HE PPDU

  • Propose to reuse the 11ac per stream CSD values for all HE PPDU

    • CSD value: [0 -400 -200 -600 -350 -650 -100 -750] ns
    • Harmonize the CSD values across all the modes
    • AGC performance difference is minor despite the duration difference between 0.8us STF (11ac and non-triggered 11ax PPDU) and 1.6us HE-STF (triggered PPDU)
  • For UL MU MIMO transmission, the per stream CSD value is based on global stream index

    • DL MU MIMO, which inherits from 11ac, already uses global stream index


When beam_change=1, Pre-HE Modulated Fields are modulated the same way as legacy

  • When beam_change=1, Pre-HE Modulated Fields are modulated the same way as legacy

  • When beam_change=0, Pre-HE Modulated Fields shall be modulated the same as HE-LTF1

    • Per antenna CSD is not specified since its impact is absorbed in the Q matrix


In UL MU transmission, per antenna CSD application uses the local index

  • In UL MU transmission, per antenna CSD application uses the local index

    • Number of Tx antennas is unknown to other STAs in UL MU transmission
    • Consistent with other modes, clean spec and implementation


Do you agree to add to 11ax SFD

  • Do you agree to add to 11ax SFD

  • 11ax shall reuse the 11ac per stream CSD values for all HE PPDU



Do you agree to add to 11ax SFD

  • Do you agree to add to 11ax SFD

  • In UL MU-MIMO transmission the per stream CSD value is based on global stream index



Do you agree to add to 11ax SFD

  • Do you agree to add to 11ax SFD

  • 11ax per antenna CSD in Pre HE modulation shall

    • reuse the 11ac per antenna CSD values when beam change =1
    • not be specified (absorbed in the Q matrix) when beam_change=0


Do you agree to add in 11ax SFD

  • Do you agree to add in 11ax SFD

  • In UL MU transmission the per antenna CSD value is based on the antenna index of each STA (i.e. local index)








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