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Hi Rojan, Thanks for the follow up comments. I think your understanding on this proposal is mostly correct. However, it is somewhat misleading when you say the AP is allowed to transmit at any time without performing contention…. It’s not “at any time” but is specifically given to the immediate response time (+ SIFS). I think there are two issues that are involved in this discussion. One is collision issue and the other is fairness issue. For the collision issue, I think having a CCA before resuming the transmission can resolve the issue. Of course, as Yongho mentioned, it is still TBD the level of CCA for better protection. For the fairness issue, regardless of the time before resuming the transmission, this transmission is happening during the TXOP that the AP has already obtained. (If this proposal is not fair to other, then with the same logic PIFS recovery
is also considered to be not fair.) So, I think fairness is not a critical issue to be considered here. Regarding your suggestion, EIFS is not meant to resolve a fairness issues among multiple STAs but is introduced to avoid possible interference during an on-going transmission sequence. In this sense, it’s not quite clear to relate length
limitation with EIFS for resolving fairness issue. So, I’m still hesitating to include your suggestion into the SP. Best regards, Young Hoon From: rojan.chitrakar@xxxxxxxxxxxxxxxx <rojan.chitrakar@xxxxxxxxxxxxxxxx>
Hi Younghoon, Thanks for the reply. Let me ask this way, to make sure I understand your proposal: Say the AP on the 2nd link obtains TXOP for 5ms and the second frame in the TXOP, ending at the 2ms mark, fails. In the baseline, the AP is allowed to transmit if CS is idle at the PIFS boundary; if it cannot transmit at the
PIFS boundary, it needs to perform a full contention. Your proposal is extending this and the
AP is allowed to transmit at any time without performing contention from 2ms to 5ms (if the transmission can complete within the TXOP) as long as the CCA is idle, is this right?
If this is right, what I am asking is: shouldn’t there be a maximum duration (e.g. within EIFS starting from 2ms), that the AP can do this? Do we really want to allow the AP to resume transmission without contention for the entire remainig
TXOP? Regards, Rojan From: Young Hoon Kwon <younghoon.kwon@xxxxxxx>
Hi Rojan and Yongho, Thank you very much for the discussion. But, I don’t think fairness is an issue for this case. Before this recovery mechanism involved, the AP MLD already obtained a TXOP. And, the TXOP owner’s error recovery shall be limited to the existing TXOP duration, which is the baseline error recovery rule (10.23.2.8). This implies that if the TBD time is longer, the AP MLD has less time to transmit for the follow up frames during the remaining TXOP duration. So, if the AP MLD can initiate a new TXOP after the TBD time, then I agree that there can be a fairness issue. However, as I mentioned here, this is not the case for this proposal. Hope this can answer for your concern. Thanks, Young Hoon From: Rojan Chitrakar <rojan.chitrakar@xxxxxxxxxxxxxxxx>
Hi Yongho, Thanks for the comment. The SP says “
… the AP MLD can continue its transmission on the link within the obtained TXOP
TBD (e.g., SIFS or PIFS) time after the failed reception of the immediate response if the channel is idle. “
My question was
how long can this TBD time be? If there is no maximum specified, that means the AP is allowed to transmit without performing full contention (IFS+backoff) for the whole TXOP; whereas a 3rd party non-AP STAs need to perform a full contention.
That’s what I meant by unfair to the non-AP STAs. Best Regards, Rojan From: Yongho Seok <yongho.seok@xxxxxxxxx>
Hi Rojan, The AP MLD is still listening to a primary channel on the link even though it failed to listen to any control response from the TXOP responder. In consequence, the AP MLD updates any physical and virtual CCA if it listens to any other transmission during the waiting time for synchronizing both links. When the AP MLD checks the CCA during the TBD time (e.g., PIFS or SIFS) for accessing the failed link, in such case the CCA may be busy. If the AP MLD can't listen to the failed link during the waiting time for synchronizing both links and tries to access the link just based on the ED during PIFS, I agree that it may have some problem like a collision. In the SP, the CCA mechanism on the link is TBD. I think that the CCA mechanism should consider the packet detection etc. It should not be just the ED based channel access. In this case, I couldn't understand what is
a fairness issue. Thanks, Yongho 2020년 6월 23일
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8:39, Rojan Chitrakar <rojan.chitrakar@xxxxxxxxxxxxxxxx>님이
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