![]() The levels of priority in EDCA are called access categories (ACs). A TXOP time interval of 0 means it is limited to a single MAC service data unit (MSDU) or MAC management protocol data unit (MMPDU). The use of TXOPs reduces the problem of low rate stations gaining an inordinate amount of channel time in the legacy 802.11 DCF MAC. If a frame is too large to be transmitted in a single TXOP, it should be fragmented into smaller frames. A TXOP is a bounded time interval during which a station can send as many frames as possible (as long as the duration of the transmissions does not extend beyond the maximum duration of the TXOP). ![]() In addition, EDCA provides contention-free access to the channel for a period called a Transmit Opportunity (TXOP). The exact values depend on the physical layer that is used to transmit the data. This is accomplished through the TCMA protocol, which is a variation of CSMA/CA using a shorter arbitration inter-frame space (AIFS) for higher priority packets. With EDCA, high-priority traffic has a higher chance of being sent than low-priority traffic: a station with high priority traffic waits a little less before it sends its packet, on average, than a station with low priority traffic. ![]() ![]() ( March 2014) ( Learn how and when to remove this template message) Please help to ensure that disputed statements are reliably sourced. Relevant discussion may be found on Talk:IEEE 802.11e-2005. This section's factual accuracy is disputed. ![]()
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