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A-MPDU status

Bit Number
u32 reference number, u16 flags, u8 delimiter CRC value, u8 reserved
Required Alignment
4 bytes

The presence of this field indicates that the frame was received as part of an a-MPDU.

The reference number is generated by the capture device and is the same across each subframe of an A-MPDU. Since the capture device might be capable of capturing multiple channels or data from multiple (concurrent) captures could be merged, the reference number is not guaranteed to be unique across different channels. As a result, applications should use the channel information together with the reference number to identify the subframes belonging to the same A-MPDU.

The following flags are defined:

0x0001 driver reports 0-length subframes
0x0002 frame is 0-length subframe (valid only if 0x0001 is set)
0x0004 last subframe is known (should be set for all subframes in an A-MPDU)
0x0008 this frame is the last subframe
0x0010 delimiter CRC error
0x0020 delimiter CRC value known: the delimiter CRC value field is valid
0xffc0 reserved

Within an A-MPDU, the subframe index can be determined by the application so it is not included, but depending on the driver reporting this may miss 0-length subframes.