VHT long training field (802.11ac) (VHT-LTF)
VHT-LTF is the long VHT training field used in VHT mode, Very High Throughput, of 802.11acWLANs.
The VHT-LTF data field consists of a sequence of symbols that initiate the demodulation of the rest of the frame, starting with the VHT signal B field. Depending on the number of streams transmitted, it consists of 1, 2, 4, 6, or 8 symbols; the number of symbols required is rounded up to the next higher value, so that a connection with five streams would require six symbols. The content of this field is also used for the channel estimation process, on which beamforming depends.