No. The operation of backoff decrement in 802.11e EDCA is significantly different from 802.11 DCF.
In DCF, transmission occurs whenever the backoff counters reach zero. In EDCA, however, transmission occurs on the first slot boundary after the backoff counter has reached zero. STAs wait for a further AIFS expiration if only the medium is busy. As I said, at slot boudaries, decrement of backoff timer and initiation of transmission can not be performed simultaneously. Jongman Heo. 2006/3/15, [EMAIL PROTECTED] <[EMAIL PROTECTED]>: > > > 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 9.9.1.3 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. > > > > > > So, > > > > 1. > > Backoff counter is resumed one slot time before the AIFS expiration. > > > > 2. > > 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? > > > > > > ps. > > 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 > > > > > > > > -- ============================= Jongman Heo
