Created an attachment (id=584) [details]
Proposed fix

When the last receive was OK, we say, tat access grant start is m_lastRxEnd +
m_sifs. When we call GetAccessGrantStartFor (), we add Aifsn * m_slotTime. So,
we start to calculate backoff AIFS later after rxEnd.

When the last receive was not ok, we may start to calculate backoff EIFS after
rxEnd.
In GetAccessGrantStart we add EifsNoDifs to last Rx end. In
GetAxxessGrantStartFor () we add as in previous case Aifsn * m_slotTime. So,
instead real EIFS we wait EIFS-SIFS