Which statements accurately describe IEEE 802.11 EDCA collision handling in a WMM-compliant
infrastructure WLAN? (Choose 2)

A.
When frames collide within a QoS STA, data frames from lower priority ACs behave (as it relates to
contention) as if there were an external collision on the wireless medium.

B.
Collisions between contending EDCAFs within a QoS STA are resolved within the QoS STA

C.
When a frame transmission on the wireless medium fails, the transmitter may not transmit another
frame from any AC or to any destination until the frame experiencing a failure is successfully transmitted
or the max retry count for that frame is reached.

D.
The WMM specification requires use of RTS/CTS as part of the EDCAF within each QoS STA to avoid
internal collisions between ACs.

E.
After frames collide within a QoS STA and the lower priority AC subsequently gains a TXOP, the retry
bit in the MAC header must be set to 1 to indicate a retry.