Generate VHT-LTF waveform
Create a VHT configuration object with an 80 MHz channel bandwidth.
cfgVHT = wlanVHTConfig; cfgVHT.ChannelBandwidth = 'CBW80';
Generate a VHT-LTF waveform.
vltfOut = wlanVHTLTF(cfgVHT); size(vltfOut)
ans = 1×2 320 1
The 80 MHz waveform is a single OFDM symbol with 320 complex output samples.
y— VHT-LTF time-domain waveform
VHT-LTF time-domain waveform, returned as an (NS × NVHTLTF)-by-NT matrix. NS is the number of time-domain samples per NVHTLTF, where NVHTLTF is the number of OFDM symbols in the VHT-LTF. NT is the number of transmit antennas.
NS is proportional to the channel bandwidth.
See VHT-LTF Processing for waveform generation details.
Complex Number Support: Yes
The very high throughput long training field (VHT-LTF) is located between the VHT-STF and VHT-SIG-B portion of the VHT packet.
It is used for MIMO channel estimation and pilot subcarrier tracking. The VHT-LTF includes one VHT long training symbol for each spatial stream indicated by the selected MCS. Each symbol is 4 μs long. A maximum of eight symbols are permitted in the VHT-LTF.
The VHT-LTF is defined in IEEE® Std 802.11ac™-2013, Section 220.127.116.11.5.
The VHT-LTF is used for MIMO channel estimation and pilot subcarrier tracking. The number of OFDM symbols in the VHT-LTF (NVHTLTF) is derived from the total number of space-time streams (NSTS_Total). NSTS_Total = ΣNSTS(u) for user u, u = 0,…, NUsers–1 and NSTS(u) is the number of space-time streams per user.
For algorithm details refer to IEEE Std 802.11ac-2013 , Section 18.104.22.168.
 IEEE Std 802.11ac™-2013 IEEE Standard for Information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Specific requirements — Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications — Amendment 4: Enhancements for Very High Throughput for Operation in Bands below 6 GHz.
 IEEE Std 802.11ac-2013 Adapted and reprinted with permission from IEEE. Copyright IEEE 2013. All rights reserved.