Generate VHT-STF waveform
Create a VHT configuration object with an 80 MHz channel bandwidth. Generate and plot the VHT-STF waveform.
cfgVHT = wlanVHTConfig; cfgVHT.ChannelBandwidth = 'CBW80'; vstfOut = wlanVHTSTF(cfgVHT); size(vstfOut); plot(abs(vstfOut)) xlabel('Samples') ylabel('Amplitude')
The 80 MHz waveform is a single OFDM symbol with 320 complex time-domain output samples. The waveform contains the repeating short training field pattern.
cfg— Format configuration
Format configuration, specified as a
osf— Oversampling factor
1(default) | scalar greater than or equal to 1
Oversampling factor, specified as a scalar greater than or equal to 1. The oversampled cyclic prefix length must be an integer number of samples. The resultant inverse fast Fourier transform (IFFT) length must be even.
y— VHT-STF time-domain waveform
VHT-STF time-domain waveform, returned as an NS-by-NT matrix. NS is the number of time-domain samples, and NT is the number of transmit antennas.
NS is proportional to the channel bandwidth.
See VHT-STF Processing for waveform generation details.
Complex Number Support: Yes
The very high throughput short training field (VHT-STF) is a single OFDM symbol (4 μs in length) that is used to improve automatic gain control estimation in a MIMO transmission. It is located between the VHT-SIG-A and VHT-LTF portions of the VHT packet.
The frequency domain sequence used to construct the VHT-STF for a 20 MHz transmission is identical to the L-STF sequence. Duplicate L-STF sequences are frequency shifted and phase rotated to support VHT transmissions for the 40 MHz, 80 MHz, and 160 MHz channel bandwidths. As such, the L-STF and HT-STF are subsets of the VHT-STF.
For a detailed description of the VHT-STF, see section 126.96.36.199.4 of IEEE® Std 802.11™-2016.
An oversampled signal is a signal sampled at a frequency that is higher than the Nyquist rate. WLAN signals maximize occupied bandwidth by using small guardbands, which can pose problems for anti-imaging and anti-aliasing filters. Oversampling increases guardband width relative to the total signal bandwidth, thereby increasing the number of samples in the signal.
This function performs oversampling by using a larger IFFT and zero pad when generating an OFDM waveform. This diagram shows the oversampling process for an OFDM waveform with NFFT subcarriers comprising Ng guardband subcarriers on either side of Nst occupied bandwidth subcarriers.
 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.