[ns] backoff decrement and transmission in 802.11e tkn code
rmoraes at fe.up.pt
Wed Mar 15 06:05:17 PST 2006
I have no knowledge about the TKN implementation. However, I don´t agree with
the interpretation of item 2. Because, when the backoff counter reach 0, the
station can transmit immediately, i.e., in the next slot time. The station
doesn´t wait for another AIFS interval.
> According to section 18.104.22.168 in the IEEE 802.11e standard,
> one and only one of the following actions is allowed at slot boundaries:
> - decrement of backoff timer, or
> - initiate transmission, or
> - backoff procedure due to internal collision, or
> - do nothing.
> Backoff counter is resumed one slot time before the AIFS expiration.
> However, since a single MAC operation per slot is permitted
> (backoff decrement or packet transmission),
> when the backoff counter decrements to 0, the station cannot
> transmit immediately, but has to wait for a further backoff
> slot if the medium is idle, or a further AIFS expiration if
> the medium is busy.
> I think that 802.11e TKN code is a good implementation of IEEE 802.11e.
> However, it seems that the implementation conforms to the requirement
> 1, but do not to the requirement 2.
> Am I correct?
> The following paper can be a good guide.
> Giuseppe Bianchi, "Understanding 802.11e Contention-Based
> Prioritization Mechanisms and Their Coexistence with Legacy 802.11
> Stations", IEEE Network, 2005
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