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Re: [STDS-802-11-TGBN] Requesting feedback on 11-25/0887r2 "CCA Issue in NPCA Operation"

Hi Yan.

Thank you for your reply.

My response are inline below

Best regards, 
Gwangho

2025년 9월 16일 (화) 오전 8:11, <li.yan16@xxxxxxxxxx>님이 작성:

Hi Gwangho,

    Thanks for initiating this topic.

    As i mentioned during your presentation, we can just add a note to clarify that the PHY-CCA.indication(Busy) is related to current operating channel. For example:

    When an OBSS PPDU is detected on BSS PCH, a PHY-CCA.indication(Busy) primitive generates and indicates the BSS PCH is busy.  And then the STA switches to NPCA PCH via PHY-CONFIG.request primitive indicating NPCA PCH. Since the previous PHY-CCA.indication(Busy) primitive only indicates the BSS PCH is busy other than the NPCA PCH. Therefore, the STA could access the channel without any limitation. 

Gwangho: 

When an OBSS PPDU is received and the PHY generates a PHY-CCA.indication(Busy) primitive, even if a PHY-CONFIG.request primitive is subsequently generated to change the Primary channel to the NPCA PCH, the previous CCA state may be maintained. As described in the Baseline text presented in Slide 4 of my contribution, the PHY shall maintain the CCA state as Busy until the end of the previously received PPDU.

17.3.12 Receive PHY
In the event that a change in the RSSI causes the status of the CCA to return to the IDLE state before the complete reception of the PSDU, as indicated by the PHY LENGTH field, the error condition shall be reported to the MAC using a PHY-RXEND.indication(CarrierLost) primitive and the PHY receiver shall return to the RX IDLE state. The CCA of the OFDM PHY shall indicate a busy medium for the intended duration of the transmitted PPDU.

This requirement also applies to the HE PHY.

27.3.24 HE receive procedure
If signal loss occurs during reception prior to completion of the PSDU reception, the error condition PHY-RXEND.indication(CarrierLost) shall be reported to the MAC. After waiting for the end of the PPDU as determined by Equation (27-146), the PHY shall set the PHY-CCA.indication(IDLE) primitive and return to the RX IDLE state.

As noted in your comment, even if the Primary channel is newly configured to NPCA PCH during PPDU reception, the PHY is a single entity, and therefore, due to the ongoing busy-hold procedure, the PHY may not be able to generate a PHY-CCA.indication(Idle) primitive for the NPCA PCH until the PPDU on the BSS PCH is complete.

To address this issue, the CCA state must ultimately be reset. This can be achieved by generating a PHY-CCARESET.request primitive. (Although another possible method is using the PHY-ABORT.request primitive, I could not find any behavior in the standard that explicitly describes the use of this primitive.)

In summary, I believe that when the Primary channel changes during NPCA operation, there is still a need to reset the CCA state, and this should be explicitly specified, for example, by generating a PHY-CCARESET.request primitive.

    BTW, according to your contribution, it's a little bit confusing to send a PHY-CCARESET.request primitive during the OBSS PPDU, because BSS PCH is indeed busy and you do not indicate which PCH(BSS PCH or NPCA PCH) this primitive applies to

Gwangho:
The CCA-RESET.request primitive instructs the PHY to reset the CCA state, and this operation is not limited to a specific channel. Once the PPDU being received on the BSS PCH is no longer relevant after switching to the NPCA PCH, it does not need to be maintained as Busy. Since an NPCA STA performing channel access on the NPCA PCH will still conduct CCA, the energy detection of the OBSS PPDU on the PCH will be sensed during that period. Therefore, even if the  CCA state is reset after switching to the NPCA PCH, the OBSS PPDU remains protected as intended by the baseline.

    In genral, when you operates on BSS PCH, PHY-CCA.indication(Busy)  primitive only indicates the BSS PCH is busy.

                     when you operates on NPCA PCH, PHY-CCA.indication(Busy)  primitive only indicates the NPCA PCH is busy

                    Such primitive does not case any influence to the PCH on which the STA does not currently operate




Best Regards！

Yan Li

Original
From: 이광호 <gwangho.lee@xxxxxxxxxx>
Date: 2025年09月16日 14:21
Subject: [STDS-802-11-TGBN] Requesting feedback on 11-25/0887r2 "CCA Issue in NPCA Operation"

Hi everyone.


I presented a contribution today (25/0887r2, "CCA Issue in NPCA Operation") during PM1.

I would like to request your feedback on this contribution.
If you have any feedback or questions, please feel free to reply to this thread


Best Regards,

Gwangho Lee (KNUT)

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