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Thanks Tomo, Let me go through your below text and come back to you as soon as possible.
By the way, the CR was discussed before, I try to finalize it as soon as possible. Best wishes Ming Gan
发件人: *** 802.11 TGax - HEW - High Efficiency WLAN *** [mailto:STDS-802-11-TGAX@xxxxxxxxxxxxxxxxx]
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Tomo Adachi Ohayou gozaimasu, Mark-san,
Good morning, Ming and Robert. I have questions to Ming and comments to Robert, too. I would appreciate if you two could
read the following and respond. Or, for the cascading case, is it strictly limited to a Trigger frame?
That's my question. Maybe it can be a TRS Control for the very end of the cascade, if the end of the cascade is DL data, UL ack (i.e. opposite to Figure 26-5—An example of an MU cascading sequence)? Ming, could you answer to this? The question is whether a TRC Control is allowed at the AP not only at the end but also
during the cascading sequence. I thought that the non-AP STA needs to be able to act as both the recipient and the originator, in other words, to respond
with an A-MPDU including an acknowledgement and a Data or Management frame (if the basic conditions such as CS, duration, etc. are met).
OK, so how about: - support bit in Clause 9: For an HE AP: Set to 1 to indicate that the AP is capable of trans- mitting an A-MPDU that is constructed following
the MU cascade sequence rules (see 26.5.3 (MU
cascading sequence)) under MU cascade operation. Set to 0 otherwise. or Reserved
[since "is capable of" doesn't really mean anything and what's a non-AP STA supposed to do with this information?] For a non-AP HE STA: Set to 1 to indicate that the non-AP STA is capable
of receiving an A-MPDU that is constructed follow- ing the MU cascade sequence rules (see 26.5.3 (MU
cascading sequence)). Set to 0 otherwise. Mark-san, I see your point where it is highlighted in yellow.
Maybe the intention was to have the non-AP STA that is capable only sets the bit to 1 when the associated AP is capable?
Ming, could you give us your opinion?
Robert, while I scanned for
“cascad" in
clause 9, D6.1, I found the following: 9.2.4.6a.4 BSR Control The Control Information subfield in a BSR Control subfield contains buffer status information used for UL MU operation (see
26.5.3 (MU cascading sequence)). The format of the subfield is shown in Figure 9-22e (Control Information subfield format in a BSR Control subfield). I think the reference should be corrected to 26.5.2 (UL MU Operation).
Please also check
“BSRs (see 26.5.3
(MU cascading sequence))”
that appears twice in Table 9-297a—Broadcast
TWT Recommendation field for a broadcast TWT element. - behaviour in Clause 26: Unless both the AP and the non-AP STA have set the MU Cascading Support subfield to 1 in the MAC Capabilities Information field
in the HE Capabilities element they transmit, an AP shall not send to the non-AP STA an A-MPDU that contains both: * a Data or Management frame, that requires acknowledgment * a Trigger frame that solicits a Data or Management frame I am almost OK with this.
Again, in my opinion, a Trigger frame can be substituted to a triggering frame that includes the TRS Control case.
Ming, are you OK with adding the above text in 26.5.3? I think the following sentence proposed in 20/980r1 can be replaced
with the above text: An MU cascading sequence shall not be used between an AP and a non-AP STA
(#CID 20732 and 20733) unless both the AP and the non-AP STA have indicated support by setting the MU Cascading Support subfield to 1 in the MAC Capabilities Information
field in the HE Capabilities element they transmit. Best regards, tomo From: Mark Rison <m.rison@xxxxxxxxxxx>
Ohayou gozaimasu Tomo-san, Thanks for your response. >
The AP requirement is true (to be more precise, it can be a TRS Control subfield instead of a Trigger frame).
Can it? A TRS Control only solicits acks, not Data/Management frames. So it's not clear to me that this forms part of a cascading sequence. say that you must support cascading if you want to send an A-MPDU containing Data frames that have a TRS Control, because I don't think that's true: even if you don't support cascading you can send such an A-MPDU, no? I see from 26.5.2.4 and Tables 9-532 and 9-531 referred therein that we can transmit Action No Ack and QoS Null frames.
Am I wrong? Ah, yes, you're right. I should have said "only solicits things that don't solicit acks". (I assume you meant 9-530, not 9-531.) Or, for the cascading case, is it strictly limited to a Trigger frame?
That's my question. Maybe it can be a TRS Control for the very end of the cascade, if the end of the cascade is DL data, UL ack (i.e. opposite to Figure 26-5—An example of an MU cascading sequence)? I agree that the AP doesn’t
need to send a TRS Control even if it supports cascading and can send it even if it doesn’t
support cascading. I tried to express that in “can”.
> But the non-AP STA requirement is not accurate. The HE TB PPDU can be transmitted only when the AP transmitted a triggering
frame. The requirement was just "if you send a TB PPDU in response to the MU PPDU it cannot contain a Data or Management frame". But as I said I don't think this is a real requirement on the non-AP STA, it's a requirement on the AP. I think we are aligned for this.
J >
If the AP sets the MU Cascading Support subfield to 1, the AP may send to a non-AP STA that sets the MU Cascading Support subfield to
1 an A-MPDU that contains a Data/Management frame and a Trigger frame or a Data/Management frame carrying a TRC Control subfield.
If all of the following conditions is met, the non-AP STA shall respond with an HE TB PPDU including an Ack or BlockAck
frame:
-
the non-AP STA sets the MU Cascading Support subfield to 1
-
the non-AP STA receives an A-MPDU that contains a Data/Management frame and a Trigger frame or a Data/Management
frame carrying a TRC Control subfield from the AP and the Data/Management solicits immediate response But there are other conditions, e.g. CS Required, power pre-correction, TB PPDU duration, so it's not always the case that you shall respond. I think expressing things as "you cannot do X unless both sides support cascading" is safer. OK. So the basic conditions in 26.5.2.3 comes first. Then, can’t
we add that as one of the items? But it's always true. What's the *new* requirement on non-AP STAs? What is wrong or missing (incomplete) in saying that the requirement for cascading is: Unless both the AP and the non-AP STA have set the MU Cascading Support subfield to 1 in the MAC Capabilities Information field in the HE Capabilities element they transmit,
an AP shall not send to the non-AP STA a PPDU that contains both: * a Data or Management frame * a Trigger frame that solicits a Data or Management frame ? As I said, (a) I think the AP can send a PPDU that contains a Data/Management frame with a TRS Control even if cascading is not supported, and (b) I think there is no specific requirement on the non-AP STA, as long as the AP obeys the requirement above. Also (c) it matches the description of the support bit in Clause 9. If (b) above is true, why does the non-AP STA need to set the MU Cascading Support subfield?
Well, the non-AP STA needs to set this so that the AP knows that it can send an A-MPDU with both a Data/Management frame and {a Trigger frame that solicits {a Data/Management frame that solicits ack}}. I think the real question is why the AP needs to set it -- what is the STA going to do with this information? I thought that the non-AP STA needs to be able to act as both the recipient and the originator, in other words, to respond
with an A-MPDU including an acknowledgement and a Data or Management frame (if the basic conditions such as CS, duration, etc. are met).
OK, so how about: - support bit in Clause 9: For an HE AP: Set to 1 to indicate that the AP is capable of trans- mitting an A-MPDU that is constructed following
the MU cascade sequence rules (see 26.5.3 (MU
cascading sequence)) under MU cascade operation. Set to 0 otherwise. or Reserved
[since "is capable of" doesn't really mean anything and what's a non-AP STA supposed to do with this information?] For a non-AP HE STA: Set to 1 to indicate that the non-AP STA is capable
of receiving an A-MPDU that is constructed follow- ing the MU cascade sequence rules (see 26.5.3 (MU
cascading sequence)). Set to 0 otherwise. - behaviour in Clause 26: Unless both the AP and the non-AP STA have set the MU Cascading Support subfield to 1 in the MAC Capabilities Information field
in the HE Capabilities element they transmit, an AP shall not send to the non-AP STA an A-MPDU that contains both: * a Data or Management frame, that requires acknowledgment * a Trigger frame that solicits a Data or Management frame Yoroshiku onegaishimasu, Mark --
Mark RISON, Standards Architect, WLAN English/Esperanto/Français Samsung Cambridge Solution Centre Tel: +44 1223 434600 Innovation Park, Cambridge CB4 0DS Fax: +44 1223 434601 ROYAUME UNI WWW:
http://www.samsung.com/uk From:
tomo.adachi@xxxxxxxxxxxxx <tomo.adachi@xxxxxxxxxxxxx>
Hi Mark,
? Strawman: Unless both the AP and the non-AP STA have set the MU Cascading Support subfield to 1 in the MAC Capabilities Information field in the HE Capabilities element they transmit: * An AP shall not send to the non-AP STA a PPDU that contains a (Basic?) Trigger frame and a Data or Management frame * A non-AP STA shall not include a Data or Management frame in the HE TB PPDU sent in response to an HE MU PPDU that contains a Data or Management frame But I'm not sure this is right, and if this strawman AP requirement is correct then I'm not sure this non-AP STA requirement is needed; it's entirely an AP constraint (as the support bit description suggests). The AP requirement is true (to be more precise, it can be a TRS Control subfield instead of a Trigger frame).
But the non-AP STA requirement is not accurate. The HE TB PPDU can be transmitted only when the AP transmitted a triggering
frame. So second strawman: Unless both the AP and the non-AP STA have set the MU Cascading Support subfield to 1 in the MAC Capabilities Information field in the HE Capabilities element they transmit,
an AP shall not send to the non-AP STA a PPDU that contains both: * a Data or Management frame * a Trigger frame that solicits a Data or Management frame ? Again, the Trigger frame can be a TRS Control subfield instead.
In other way, I think we can say as follows to avoid negative _expression_:
If the AP sets the MU Cascading Support subfield to 1, the AP may send to a non-AP STA that sets the MU Cascading Support
subfield to 1 an A-MPDU that contains a Data/Management frame and a Trigger frame or a Data/Management frame carrying a TRC Control subfield.
If all of the following conditions is met, the non-AP STA shall respond with an HE TB PPDU including an Ack or BlockAck
frame:
-
the non-AP STA sets the MU Cascading Support subfield to 1
-
the non-AP STA receives an A-MPDU that contains a Data/Management frame and a Trigger frame or a Data/Management
frame carrying a TRC Control subfield from the AP and the Data/Management solicits immediate response Could you polish it, Mark?
Best regards, tomo From: adachi tomoko(足立
朋子 ○RDC□IT研○WSL)
Hi Mark,
The 1st sentence in the 2nd para is explaining the condition that both sides need to have the capability
support. From my understanding, the AP shall not transmit data to a STA while triggering the STA that does not have the capability.
The STA shall indicate its capability to the AP and may transmit UL data if it supports the sequence and if it has buffered
data. My apologies to rough response. I am about to stop working today.
Let me think about the description further how to explain without saying
“shall not”…
Best regards, tomo From: Mark Rison <m.rison@xxxxxxxxxxx>
Thanks for the reminder. I'm not 100% sure where we are with this. 20/0980r1 says: An MU cascading sequence is a frame exchange sequence between an AP and one or more non-AP STAs carried in an HE MU PPDU in the downlink and
HE TB PPDU in the uplink where both the HE MU PPDU and the HE TB PPDU contain at least one Data frame or Management frame. An example of an MU cascading sequence is shown in Figure 26-5 (An example of an MU cascading sequence)
where the HE MU PPDU contains a Data frame and a triggering frame and the HE TB PPDU contains an Ack or BlockAck frame and a Data frame. (#CID 20732, 20733 and 21450) An MU cascading sequence shall not be used between an AP and a non-AP STA
(#CID 20732 and 20733) unless both the AP and the non-AP STA have indicated support by setting the MU Cascading Support subfield to 1 in the MAC Capabilities Information
field in the HE Capabilities element they transmit. The A-MPDU may additionally contain one or more MPDUs and is constructed following the rules defined in 26.11 (Setting TXVECTOR parameters for an HE PPDU). So what is the intent of the second para (the one with the only normative requirement ("shall not"))? The AP has no direct control over what the non-AP STA includes it its TB PPDU, so is this actually a requirement on the non-AP STA? "A STA shall not transmit an HE TB PPDU that contains a Data or Management frame in response to an HE MU PPDU that contains a Data or Management frame unless both the AP and the non-AP STA have set the support bit."? But that's not compatible with the description of the support bit, which is entirely in terms of the downlink rules: For an HE AP: Set to 1 to
indicate that the AP is capable of trans- mitting
an A-MPDU that is constructed following the MU cascade sequence rules (see 26.5.3 (MU
cascading sequence)) under MU cascade operation. Set to 0 otherwise. For a non-AP HE STA: Set to 1 to
indicate that the non-AP STA is capable
of receiving
an A-MPDU that is constructed follow- ing the MU cascade sequence rules (see 26.5.3 (MU
cascading sequence)). Set to 0 otherwise. To make progress, I suggest that the "shall" should be expressed as the actual requirement, not a vague "shall not do cascading". Can someone fill in the blanks in: Unless both the AP and the non-AP STA have set the MU Cascading Support subfield to 1 in the MAC Capabilities Information field in the HE Capabilities element they transmit: * An AP shall not
<what?> * A non-AP STA shall not
<what?> ? Strawman: Unless both the AP and the non-AP STA have set the MU Cascading Support subfield to 1 in the MAC Capabilities Information field in the HE Capabilities element they transmit: * An AP shall not send to the non-AP STA a PPDU that contains a (Basic?) Trigger frame and a Data or Management frame * A non-AP STA shall not include a Data or Management frame in the HE TB PPDU sent in response to an HE MU PPDU that contains a Data or Management frame But I'm not sure this is right, and if this strawman AP requirement is correct then I'm not sure this non-AP STA requirement is needed; it's entirely an AP constraint (as the support bit description suggests). So second strawman: Unless both the AP and the non-AP STA have set the MU Cascading Support subfield to 1 in the MAC Capabilities Information field in the HE Capabilities element they transmit,
an AP shall not send to the non-AP STA a PPDU that contains both: * a Data or Management frame * a Trigger frame that solicits a Data or Management frame ? Thanks, Mark --
Mark RISON, Standards Architect, WLAN English/Esperanto/Français Samsung Cambridge Solution Centre
Tel: +44 1223 434600 Innovation Park, Cambridge CB4 0DS Fax: +44 1223 434601 ROYAUME UNI WWW:
http://www.samsung.com/uk From: *** 802.11 TGax
- HEW - High Efficiency WLAN *** <STDS-802-11-TGAX@xxxxxxxxxxxxxxxxx>
On Behalf Of Tomo Adachi Hi Mark, Ming,
Sorry for my late reply…
I wasn’t
attending the call when 20/0980 was discussed and thought that it will be converged.
But, is this topic still with no conclusion?
My position is that I’m
happy with the change made in 20/0980r1. I do think that there are cases when an AP sends ack/BA+Data in DL.
For more extreme case, when the data frames been exchanged have No Ack policy, only those data frames can appear in both
UL and DL. So the essential for the MU cascading is the first sentence in the first para, i.e.,
“a frame exchange
sequence between an AP and one or more non-AP STAs carried in an HE MU PPDU in the downlink and HE TB PPDU in the uplink where both the HE MU PPDU and the HE TB PPDU contain at least one Data frame or Management frame”.
And I’m
OK if the capability condition, which is the first sentence in the second para, is merged with the first para.
(You may need to clarify what
“the A-MPDU”
is for the current second sentence in the second para. My suggestion will be to say like
“The A-MPDU
*within the MU cascading sequence* may additionally contain one or more MPDUs and is constructed following the rules defined in 26.11 (Setting TXVECTOR parameters for an HE PPDU).”)
Mark may want to clarify what is required when the STA declares the support. And I agree that is missing.
My understanding is that, the STA is required to be capable of generating both ack/BA and data/management frames and transmit
them in an A-MPDU. You may think that it conflicts with what I said above, but this is because the Ack policy of the MPDUs within the MU cascading
sequence is not limited to No Ack. So, in case of the (implicit) BAR carried in the A-MPDU, the STA has to respond to it.
Mark, do you agree if the requirement on the non-AP STA side is clarified?
Best regards, tomo From: Mark Rison <m.rison@xxxxxxxxxxx>
>
Regarding MU cascading Look, we just need to agree what MU cascading is, i.e. the thing you can only do if both sides declare support for the feature. If we cannot agree, then the feature is clearly underspecified and broken. Is it a frame exchange sequence between an AP and one or more non-AP STAs
carried in an HE MU PPDU in the downlink and HE TB PPDU in the uplink and characterized by the
exchange of Control, Data and/or Management frames in both directions or is it that you transmit an A-MPDU to a non-AP STA that includes an Ack or BlockAck frame together
with a triggering frame ? And is the requirement only on tx for the AP and only on rx for the non-AP STA, per Clause 9's For an HE AP: Set to 1 to indicate that the AP is capable of trans- mitting an A-MPDU that is constructed following
the MU cascade sequence rules (see 26.5.3 (MU
cascading sequence)) under MU cascade operation. Set to 0 otherwise. For a non-AP HE STA: Set to 1 to indicate that the non-AP STA is capable
of receiving an A-MPDU that is constructed follow- ing the MU cascade sequence rules (see 26.5.3 (MU
cascading sequence)). Set to 0 otherwise. ? >
Regarding 20-0981 This was my email to Alfred: So, is this what 26.3.1 is trying to say? — Level 1: dynamic fragments shall be in non-A-MPDUs (no support for dynamic fragments in A-MPDUs that do not contain an S-MPDU) —
Level 2: dynamic fragments may be in an A-MPDU that does not contain an S-MPDU, subject to the following conditions: - There shall be no more than one dynamic fragment of any given MSDU or A-MSDU in the A-MPDU, and the MSDU or A-MSDU shall be under a block ack agreement
[i.e. you can have dynfrags for multiple MSDUs/A-MSDUs, as long as they’re all for different MSDUs/A-MSDUs, i.e. different SN+UP?] - They shall be no more than one dynamic fragment of any given MMPDU
[or maybe the intent is “no more than one dynamic fragment in a Management frame? Can you have multiple dynfrags of MMPDUs as
long as the SNs are different?] [can you have this together with dynfrags of MSDUs/A-MSDUs?] [I’m guessing what the existing text is trying to say,
because it’s not clear to me what
“each”
means and how an MMPDU can be sent under a BA agreement in “support for up to one dynamic fragment for each MSDU, each A-MSDU (if
supported by the recipient) and one MMPDU (see 26.6.3 (Multi-TID A-MPDU and ack-enabled single-TID A-MPDU)) in an A-MPDU that does not contain an S-MPDU, where the A-MPDU contains at least one dynamic fragment and is sent under an HT-immediate block ack agreement.”] — Level 3: dynamic fragments may be in an A-MPDU that does not contain an S-MPDU, subject to the following conditions: - There shall be no more than 4 dynamic fragments of any given MSDU or A-MSDU in the A-MPDU, and the MSDU or A-MSDU shall be under a block ack agreement - They shall be no more than one dynamic fragment of any given MMPDU [Ditto. Seems it’s same as level 2 except you can have
4 dynfrags for each MSDU/A-MSDU?] Thanks, Mark P.S.: The xrefs in The TWT responding STA should solicit buffer status reports from the TWT requesting
STA at the start of the TWT SP following the procedure described in 26.5.3 (MU cascading sequence) or as
described in 26.5.7 (NDP feedback report procedure). look wrong to me. --
Mark RISON, Standards Architect, WLAN English/Esperanto/Français Samsung Cambridge Solution Centre Tel: +44 1223 434600 Innovation Park, Cambridge CB4 0DS Fax: +44 1223 434601 ROYAUME UNI WWW:
http://www.samsung.com/uk From: *** 802.11 TGax
- HEW - High Efficiency WLAN *** <STDS-802-11-TGAX@xxxxxxxxxxxxxxxxx>
On Behalf Of Ganming (Ming) Hello Alfred Regarding MU cascading, I provided several solutions to address this vague issue in previous CR phases. But It seems most of people want to keep
the existing text and do not want to do any change. Finally, I chose to reject this comment. However, it did not satisfy the commenter Mark Rison such that he raised this comment again and again. In the last call, I was aware there was discussion and converged
it to ack+trigger is the essential of MU cascading. However, I still did not know the story behind it. In my opinion, it may not be exact. For example, ack+data also could be the essential of MU cascading. Regarding 20-0981, which email is making the general description clear? Mark , Alfred, could you provide your thought here? Best wishes, Ming Gan 发件人: Alfred Asterjadhi [mailto:asterjadhi@xxxxxxxxx]
Hello Ming,
Please find my thoughts inline. Regards, Alfred On Thu, Jul 2, 2020 at 8:16 AM Ganming (Ming) <ming.gan@xxxxxxxxxx> wrote:
-- Alfred Asterjadhi, PhD IEEE802.11 TGbe Chair, Qualcomm Technologies Inc. Cell #: +1 858 263 9445 Office #: +1 858 658 5302 To unsubscribe from the STDS-802-11-TGAX list, click the following link:
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