Documentation

wlanLLTF

Generate L-LTF waveform

所有的页面崩溃

Syntax

y = wlanLLTF(cfg)

Description

example

y= wlanLLTF(cfg)generates anL-LTF[1]time-domain waveform for the specified configuration object.

Examples

collapse all

Open Live Script

Generate the L-LTF for a 40 MHz single antenna VHT packet.

cfgVHT = wlanVHTConfig('ChannelBandwidth',“CBW40”); y = wlanLLTF(cfgVHT); size(y)
ans =1×2320 1
plot(abs(y)) xlabel('Samples') ylabel('Amplitude')

The output L-LTF waveform contains 320 time-domain samples for a 40 MHz channel bandwidth.

Input Arguments

collapse all

Format configuration, specified as awlanVHTConfig,wlanHTConfig, orwlanNonHTConfigobject. For a specified format, thewlanLLTFfunction uses only the object properties indicated.

Transmission Format Configuration Object Applicable Object Properties

VHT

 wlanVHTConfig

ChannelBandwidth,NumTransmitAntennas

HT

 wlanHTConfig

ChannelBandwidth,NumTransmitAntennas

non-HT

See note.		 wlanNonHTConfig

ChannelBandwidth,NumTransmitAntennas
Note:

  1. For non-HT format, when channel bandwidth is 5 MHz or 10 MHz,NumTransmitAntennasis not applicable because only one transmit antenna is permitted.

Example:wlanVHTConfig

Output Arguments

collapse all

L-LTFtime-domain waveform, returned as anNS-by-NTmatrix.NSis the number of time-domain samples, andNTis the number of transmit antennas.

NSis proportional to the channel bandwidth. The time-domain waveform consists of two symbols.

ChannelBandwidth NS
'CBW5','CBW10','CBW20' 160
“CBW40” 320
'CBW80' 640
'CBW160' 1280

Data Types:double
Complex Number Support:Yes

More About

collapse all

L-LTF

The legacy long training field (L-LTF) is the second field in the 802.11™ OFDM PLCP legacy preamble. The L-LTF is a component of VHT, HT, and non-HT PPDUs.

Channel estimation, fine frequency offset estimation, and fine symbol timing offset estimation rely on the L-LTF.

The L-LTF is composed of a cyclic prefix (CP) followed by two identical long training symbols (C1 and C2). The CP consists of the second half of the long training symbol.

The L-LTF duration varies with channel bandwidth.

Channel Bandwidth (MHz) Subcarrier Frequency Spacing,ΔF(kHz) Fast Fourier Transform (FFT) Period (TFFT= 1 /ΔF) Cyclic Prefix or Training Symbol Guard Interval (GI2) Duration (TGI2=TFFT/ 2) L-LTF Duration (TLONG=TGI2+ 2 ×TFFT)
20, 40, 80, and 160 312.5 3.2 μs 1.6 μs 8 μs
10 156.25 6.4 μs 3.2 μs 16 μs
5 78.125 12.8 μs 6.4 μs 32 μs

Algorithms

TheL-LTFis two OFDM symbols long and follows the L-STF of the preamble in the packet structure for the VHT, HT, and non-HT formats. For algorithm details, refer to IEEE Std 802.11ac™-2013[1], Section 22.3.8.2.3 and IEEE Std 802.11-2012[2], Section 20.3.9.3.4.

References

[1] 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.

[2]IEEE Std 802.11™-2012 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.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

See Also

||||||

Introduced in R2015b

[1]IEEE®Std 802.11-2012 Adapted and reprinted with permission from IEEE. Copyright IEEE 2012. All rights reserved.

WLAN Toolbox Documentation
金宝app

Try MATLAB, Simulink, and Other Products

Get trial now