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Hi, To address some of the clarification questions we uploaded R4 with minor changes to SP text: https://mentor.ieee.org/802.11/dcn/20/11-20-1009-04-00be-multi-link-hidden-terminal-followup.pptx The revised SP text now reads as (changes relative to R3 are highlighted) : Do you agree
to add the following to 11be SFD R1: if during a transmission of a STA (STA-1) of a non-STR non-AP MLD, another STA (STA-2) of the same MLD cannot detect its medium state when required (due to STA-1’s
UL transmission interference), STA-2 shall start a MediumSyncDelay timer at the end of
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the MediumSyncDelay timer expires after a duration value that is either assigned by AP or specified in spec or if at least either of the following events happens:
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any received PPDU with a valid MPDU
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a received PPDU with a valid TxOP_duration whichever happens first
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while the MediumSyncDelay timer is running the STA is only allowed to attempt to initiate up to number of TxOPs assigned by the AP (at least 1) and shall attempt to initiate that TxOP with the transmission of an RTS frame using
regular EDCA backoff using baseline CCA but a TBD ED threshold value
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The TBD ED threshold value has a default value specified in the spec (e.g., -62dBm) but can also be assigned by the AP MLD within a limited range such as between -82dBm and
-62dBm
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If the channel was busy immediately after the blind period, additional TBD rules to use RTS may apply. Note:
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If either the intra-BSS NAV or the inter-BSS NAV is non-zero in STA-2 at the end of transmission of STA-1, STA-2 does not transmit any PPDU using EDCA until the NAV expires.
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If either the intra-BSS NAV or the inter-BSS NAV is non-zero in STA-2 at the end of transmission of STA-1, there could be further TBD conditions and requirements to expire the MediumSyncDelay timer. Please let us know of any concerns. Regards, Dibakar From: Das, Dibakar <dibakar.das@xxxxxxxxx> Hi Ming, Not sure how you came to the conclusion that this scheme allows a STA to transmit even when its NAV is set. If the STA has already set its NAV, clearly it cannot transmit during that time. Regards, Dibakar From: Ganming (Ming) <ming.gan@xxxxxxxxxx>
Hi Dibakar, It indeed breaks the existing regulatory. The baseline is that the STA can not do EDCA channel access no matter what ED threshold it uses if the NAV is not zero. Before
or during the blindness period, the STA could be set a NAV by other frame. However, it allows the STA to do channel access even if it has nonzero NAV in this case. Moreover, allowing this TBD threshold may change lots of MAC schemes. The problem of non-STR blindness could be addressed by other baseline scheme. Best wishes Ming Gan
发件人:
Das, Dibakar [mailto:dibakar.das@xxxxxxxxx]
Hi Ming, In our understanding this scheme does not break any existing regulatory scheme because unlike PIFS type mechanism it just reuses EDCA and does not give additional advantage to the STA relative to
baseline. Maybe you can clarify specifically what breaks. The actual number of TBDs is not very high. ED threshold and number of RTS is expected to be configured by AP so only its signaling is TBD. Inter/intra NAV is part
of an additional rule that we can consider when we discuss Sharan’s presentation; nothing breaks without it. So, at its core, the solution is as simple as the NAVsync rule in baseline + allowing one or more RTS transmissions (so as not to lose MLO benefits)
+ having an AP-configured ED threshold while the timer is running. We think this is an R1 feature if we consider non-STR blindness as a problem.
Regards, Dibakar From: Ganming (Ming) <ming.gan@xxxxxxxxxx>
Hello Dibakar Thanks for preparing this sp. In my mind, it is a little bit hurry. This sp changes the exiting Channel Access rule, allowing EDCA channel access in case of non-zero
NAV, and may violate regulation like PIFS access for multi-link. I think we should consider some schemes which follow the existing EDCA rule first and then consider those fancy schemes. Moreover, there are lots of TBD in this sp, like exception, ED threshold,
inter/intra NAV, the number of RTS/TXOP, RTS rule and so on. It seems to need more discussion. By the way, do you consider this in r2? Best wishes, Ming Gan
发件人:
Das, Dibakar [mailto:dibakar.das@xxxxxxxxx]
Hi all, We have made revisions to the submission 1009 based on the feedback received offline and uploaded r3: https://mentor.ieee.org/802.11/dcn/20/11-20-1009-03-00be-multi-link-hidden-terminal-followup.pptx Summary of the discussion:
The basic idea is a STA starts a timer following a blindness event so as to avoid collision with a hidden transmission. During this time, the STA (1) can still attempt to initiate a TXOP by transmitting
limited number of RTS frames so as to regain some channel access benefits and (2) in managed BSS scenarios use a lower ED threshold that is configured by AP. During offline discussion Yunbo and Sharan pointed out that further discussion may be needed for the
case when (a) the STA detects medium to be busy right after blindness event ends or (b) the NAV is non-zero at the end of the blindness event. As such we revised the text so we could discuss those points in later contributions from others. The revised SP reads as below with the changes highlighted in green. Let me know if you have concerns.:
whichever happens first
Note:
Regards, Dibakar
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