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Re: [STDS-802-11-TGBE] question on 11-21/1229r2

Hi Zinan,

You are right about TF padding, but there is an upper bound for the padding duration and it’s used to full fill TF processing which is different with the concern of the implementation in the CR. for non-TB sounding, STA can chose a rate that fit its hardware limitation such that the STA could response within SIFS. This is exactly the point to add a capability for TB sounding where AP can poll with a high rate which cannot be full filled within SIFS.

 

For capability element, IMO, it’s better to keep PHY related ones within PHY capability element.

 

BRs,

Xiaogang.

 

From: Zinan Lin <Zinan.Lin@xxxxxxxxxxxxxxxx>
Sent: Thursday, October 7, 2021 8:22 AM
To: Chen, Xiaogang C <xiaogang.c.chen@xxxxxxxxx>; STDS-802-11-TGBE@xxxxxxxxxxxxxxxxx
Subject: question on 11-21/1229r2

 

Hi Xiaogang,

 

Thank you for presenting 11-21/1229r2 in the last week’s Joint meeting. It is an interesting topic.

 

Regarding CID 5770, I am still confused by the motivation of adding TB Sounding Feedback Rate Limit subfield in the EHT PHY Capabilities element.

a.       I am not sure why the STA has to indicate its TB Sounding Feedback Rate Limit capability to the AP

                                       i.      For TB-based sounding, non-AP STAs can start process CSI feedback after NDP frame. Other solutions are available for AP to provide extra processing time for non-AP STAs. For example, in 11ax, there is a Padding field in Trigger frame (Figure 9-64a—Trigger frame format and 26.5.2.2.3 Padding for a triggering frame in 802.11ax D8.0) ) and User Info field with AID12 4095 as padding field (Table 9-29h—AID12 subfield encoding). Both of these can be used to give the non-AP STA more processing time.

                                     ii.      For non-TB based sounding, STA can choose the MCS/Nss to transmit the feedback. Note the STA needs to start processing CSI feedback and responding right after NDP within SIFS time in this case.

 

b.       There are only two reserved bits remained in EHT PHY Capabilities element. Why it has to use the precious bit in EHT PHY Capabilities element to indicate the TB Sounding Feedback Rate Limit? 

                                       i.      There are 11 reserved bits in EHT MAC Capabilities element. Is it better to use the reserved bit in EHT MAC Capabilities element if this capability has to be indicated to the AP?

 

 

Best regards,

Zinan

 

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