Thread Links | Date Links | ||||
---|---|---|---|---|---|
Thread Prev | Thread Next | Thread Index | Date Prev | Date Next | Date Index |
--- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
Hello Matt, I think you make a reasonable argument, and I've checked with the commenter and he agrees.
So I propose to resolve CID 2187 as follows: REJECTED In the case of reaching
backoff = 0, if a STA for some reason does NOT initiate a transmission, then it should always instead do a new
backoff. If this is not done, then the STA is left with the condition that whenever the medium next becomes free, then: a) it will have permission to initiate that suspended transmission. b) any number of other STAs might have reached the same condition in the meantime because they had the same event occur while this STA was waiting for a free medium The result is that multiple STA all can initiate at exactly the same time - that is, if the gating condition is the end of some activity on the air, then all of the waiting STAs will see that same gating condition
at the same time. And all of them will then start a suspended transmission at the same time. I.e. this
behavior will cause an alignment of their states which, absent this condition, would have been randomly aligned states. E.g. if five STA are waiting to transmit with different
backoff values then as long as the primary is idle, they all count
backoff and each reaches ZERO at a different time, yet each chooses to not transmit because when it reaches 0, it sees a busy on some secondary Then, at some point, that secondary becomes IDLE and then all five STAs come blasting out at the same time. So whenever a
backoff=0 is not used and there is a non-empty TX queue, then a new
backoff should be invoked. However, we still have a problem, because 10.23.2.4 only allows "Invoke the
backoff procedure due to an internal collision." not "Invoke the
backoff procedure because you could but chose not to transmit." So some changes are going to be necessary in 10.23.2.4 anyway. Is there agreement that in the "could but chose not to transmit" case the
backoff does not change CW[AC] (i.e. not doubled, not reset), since it is neither failure nor success? 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:
Matthew Fischer <matthew.fischer@xxxxxxxxxxxx>
Mark, Thanks. I finally found that definition that you cite. I see that this definition matches the language that is being replaced by TXOP, so ok, sort of. That is, I can see the logical equivalence of "initiate frame exchange" with TXOP, so the substitution seems ok, but I do not like this definition of TXOP. I.e. the definition looks like a moment in time, but there are things like TXOP duration and TXOP limit. The definition claims to be more than a moment, as in "interval" but then the definition sounds like someone can initiate frame exchanges at any time within a TXOP, but that's not true. There are limitations. But maybe the definition does not need to mention that, so I probably don't care too much about it. BUT I still question the other change: Specifically, in the case of reaching backoff = 0, if a STA for some reason does NOT initiate a transmission, then it should always instead do a new backoff. If this is not done, then the STA is left with the condition that whenever the medium next becomes free, then: a) it will have permission to initiate that suspended transmission. b) any number of other STAs might have reached the same condition in the meantime because they had the same event occur while this STA was waiting for a free medium The result is that multiple STA all can initiate at exactly the same time - that is, if the gating condition is the end of some activity on the air, then all of the waiting STAs will see that same gating condition
at the same time. And all of them will then start a suspended transmission at the same time. I.e. this behavior will cause an alignment of their states which, absent this condition, would have been randomly aligned states. E.g. if five STA are waiting to transmit with different backoff values then as long as the primary is idle, they all count backoff and each reaches ZERO at a different time, yet each chooses to not transmit because when it reaches 0, it sees a busy on some secondary Then, at some point, that secondary becomes IDLE and then all five STAs come blasting out at the same time. I.e. the proposed language does create a spoiled party This is why I believe that whenever a backoff=0 is not used and there is a non-empty TX queue, then a new backoff should be invoked. Note that if the TX queue is empty, and backoff = 0, then no new backoff is needed because the gating event for transmission initiation is not a common network event. I.e. the gating event for transmission in this case is the entry of a new item into an empty TX queue at a single STA and that is a random event observed by only that one STA. Matthew Fischer Nice Guy Broadcom Inc. +1 408 543 3370 office On Sun, Aug 28, 2022 at 7:59 AM Mark Rison <m.rison@xxxxxxxxxxx> wrote:
To unsubscribe from the STDS-802-11-TGM list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-11-TGM&A=1 |