An extremely high throughput transmission — legacy preamble, universal signal field, EHT preamble, data, and a packet extension.
Reading a capture
Its fixed preamble cost is higher again than HE's, which continues a trend worth stating plainly: every generation has made the first microseconds of a transmission more expensive and the microseconds after them cheaper. That trade is only worth taking if frames are long, which is why aggregation stopped being an optimisation and became the assumption.
Subfields
U-SIG — Two OFDM symbols carrying a version number and the parameters every generation needs, in a layout later amendments must preserve.
EHT-SIG — Per-user signalling: which stations are in this transmission, on which resource units, at which rates.
EHT-STF — Short training for the EHT portion, retuning the receiver's gain after the legacy fields.
EHT-LTF — Long training fields, one set per spatial stream, for channel estimation.
Data field — The PSDU, modulated at the rate named in the preamble.
Packet Extension — Airtime after the data that carries nothing, giving the receiver time to finish processing.