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wlanVHTLTF

Generate VHT-LTF waveform

Description

example

y = wlanVHTLTF(cfg) generates a VHT-LTF [1] time-domain waveform for the specified configuration object. See VHT-LTF Processing for waveform generation details.

Examples

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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.

Input Arguments

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Format configuration, specified as a wlanVHTConfig object.

Output Arguments

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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.

ChannelBandwidthNS
'CBW20'80
'CBW40'160
'CBW80'320
'CBW160'640

See VHT-LTF Processing for waveform generation details.

Data Types: double
Complex Number Support: Yes

More About

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VHT-LTF

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.

For a detailed description of the VHT-LTF, see section 21.3.8.3.5 of IEEE® Std 802.11™-2016.

Algorithms

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VHT-LTF Processing

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.

NSTS_TotalNVHTLTF
11
22
34
44
56
66
78
88

For algorithm details refer to IEEE Std 802.11ac™-2013 [1], Section 22.3.4.7.

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.

Extended Capabilities

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

Introduced in R2015b

[1] IEEE Std 802.11ac-2013 Adapted and reprinted with permission from IEEE. Copyright IEEE 2013. All rights reserved.