[ns] backoff decrement and transmission in 802.11e tkn code
jongman.heo at gmail.com
Wed Mar 15 04:40:22 PST 2006
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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