Generate L-STF waveform
y = wlanLSTF(cfg)
Generate the L-STF waveform for a 40 MHz single antenna VHT packet.
Create a VHT configuration object. Use this object to generate the L-STF waveform.
cfgVHT = wlanVHTConfig('ChannelBandwidth','CBW40'); y = wlanLSTF(cfgVHT); size(y)
ans = 1×2 320 1
plot(abs(y)) xlabel('Samples') ylabel('Amplitude')
The output L-STF waveform contains 320 samples for a 40 MHz channel bandwidth.
cfg— Format configuration
|Transmission Format||Applicable Object Properties|
y— L-STF time-domain waveform
(L-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. The time-domain waveform consists of two symbols.
Complex Number Support: Yes
The legacy short training field (L-STF) is the first field of the 802.11™ OFDM PLCP legacy preamble. The L-STF is a component of VHT, HT, and non-HT PPDUs.
The L-STF duration varies with channel bandwidth.
|Channel Bandwidth (MHz)||Subcarrier Frequency Spacing, ΔF (kHz)||Fast Fourier Transform (FFT) Period (TFFT = 1 / ΔF)||L-STF Duration (TSHORT = 10 × TFFT / 4)|
|20, 40, 80, and 160||312.5||3.2 μs||8 μs|
|10||156.25||6.4 μs||16 μs|
|5||78.125||12.8 μs||32 μs|
Because the sequence has good correlation properties, it is used for start-of-packet detection, for coarse frequency correction, and for setting the AGC. The sequence uses 12 of the 52 subcarriers that are available per 20 MHz channel bandwidth segment. For 5 MHz, 10 MHz, and 20 MHz bandwidths, the number of channel bandwidths segments is 1.
The L-STF is two OFDM symbols long and is the first field in the packet structure for the VHT, HT, and non-HT OFDM formats. For algorithm details, refer to IEEE Std 802.11ac™-2013 , Section 220.127.116.11.2.
 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 802.11-2012 Adapted and reprinted with permission from IEEE. Copyright IEEE 2012. All rights reserved.