wlanVHTLTFDemodulate

(To be removed) Demodulate VHT-LTF waveform

wlanVHTLTFDemodulate will be removed in a future release. Use wlanVHTDemodulate instead. For more information on updating your code, see Version History. (since R2026a)

Syntax

sym = wlanVHTLTFDemodulate(rx,cfg)

sym = wlanVHTLTFDemodulate(rx,cbw,numSTS)

sym = wlanVHTLTFDemodulate(___,symOffset)

Description

sym = wlanVHTLTFDemodulate(rx,cfg) returns a demodulated VHT-LTF waveform y by demodulating time-domain input signal rx for very high throughput (VHT) transmission parameters cfg.

sym = wlanVHTLTFDemodulate(rx,cbw,numSTS) specifies channel bandwidth cbw and number of space-time streams numSTS.

sym = wlanVHTLTFDemodulate(___,symOffset) specifies the OFDM symbol offset as a fraction of the cyclic prefix length.

Examples

Demodulate Received VHT-LTF Signal

Create a VHT format configuration object.

vht = wlanVHTConfig;

Generate a VHT-LTF signal.

txVHTLTF = wlanVHTLTF(vht);

Add white noise to the signal.

rxVHTLTF = awgn(txVHTLTF,1);

Demodulate the received signal.

y = wlanVHTLTFDemodulate(rxVHTLTF,vht);

Input Arguments

rx — Received time-domain signal

complex-valued matrix

Received time-domain signal, specified as a complex-valued matrix of size N_s-by-N_r.

• N_s is the number of time-domain samples. If N_s is not an integer multiple of the OFDM symbol length, L_s, for the specified field,then the function ignores the remaining mod(Ns,Ls) symbols.

• N_r is the number of receive antennas.

Data Types: double | single
Complex Number Support: Yes

cfg — VHT format configuration

wlanVHTConfig object

VHT format configuration, specified as a wlanVHTConfig object.

cbw — Channel bandwidth

'CBW20' | 'CBW40' | 'CBW80' | 'CBW160'

Channel bandwidth, specified as 'CBW20', 'CBW40', 'CBW80', or 'CBW160'. If the transmission has multiple users, the same channel bandwidth is applied to all users.

Data Types: char | string

numSTS — Number of space-time streams

integer from 1 to 8 | 1-by-N_Users vector of integers from 1 to 4

Number of space-time streams in the transmission, specified as a scalar or vector.

• For a single user, the number of space-time streams is an integer scalar from 1 to 8.

• For multiple users, the number of space-time streams is a 1-by-N_Users vector of integers from 1 to 4, where the vector length, N_Users, is an integer from 1 to 4.

Example: [1 3 2] indicates that one space-time stream is assigned to user 1, three space-time streams are assigned to user 2, and two space-time streams are assigned to user 3.

Note

The sum of the space-time stream vector elements must not exceed eight.

symOffset — OFDM symbol sampling offset

0.75 (default) | scalar in the interval [0, 1]

OFDM symbol sampling offset, as a fraction of the cyclic prefix length, specified as a scalar in the interval [0, 1].

The value that you specify indicates the start location for OFDM demodulation relative to the beginning of the cyclic prefix.

Example: 0.45

Data Types: double | single

Output Arguments

sym — Demodulated frequency-domain signal

complex-valued array

Demodulated frequency-domain signal, returned as a complex-valued array of size N_sc-by-N_sym-by-N_r.

• N_sc is the number of active occupied subcarriers in the demodulated field.

• N_sym is the number of OFDM symbols.

• N_r is the number of receive antennas.

Data Types: double | single
Complex Number Support: Yes

More About

VHT-LTF

The very high throughput long training field (VHT-LTF) is between the VHT-STF and VHT-SIG-B portion of the VHT packet. This diagram¹ shows the VHT-LTF in a VHT packet.

Receivers use this field 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 modulation and coding scheme (MCS). Each symbol is 4 μs long. The VHT-LTF consists of eight symbols at most.

For a detailed description of the VHT-LTF, see Section 21.3.8.3.5 of IEEE^® Std 802.11™-2020.

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™.

Version History

Introduced in R2015b

R2026a: To be removed

wlanVHTLTFDemodulate will be removed in a future release. Use wlanVHTDemodulate instead. There are differences between the two functions that require updates to your code. See the Update Code for VHT Reception topic for more information.

R2024a: Single precision support

This function supports single-precision values for its numeric input arguments.