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wlanHTOFDMInfo

Return OFDM information for HT format

Syntax

info = wlanHTOFDMInfo(field,cfg)
info = wlanHTOFDMInfo(field,cbw,gi)
info = wlanHTOFDMInfo(field,cbw)

Description

example

info = wlanHTOFDMInfo(field,cfg) returns a structure, info, containing orthogonal frequency-division multiplexing (OFDM) information for the input field, field, and the high-throughput (HT) format configuration object cfg.

example

info = wlanHTOFDMInfo(field,cbw,gi) returns OFDM information for the specified channel bandwidth cbw and guard interval gi. To return OFDM information for the HT-Data field when the format configuration is unknown, use this syntax.

example

info = wlanHTOFDMInfo(field,cbw) returns OFDM information for the specified channel bandwidth cbw. To return OFDM information for any field other than HT-Data when the format configuration is unknown, use this syntax.

Examples

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Perform OFDM demodulation on the HT-LTF and extract the data and pilot subcarriers.

Generate a WLAN waveform for a HT format configuration.

cfg = wlanHTConfig;
bits = [1; 0; 0; 1];
waveform = wlanWaveformGenerator(bits,cfg);

Obtain the field indices and extract the HT-LTF.

ind = wlanFieldIndices(cfg);
rx = waveform(ind.HTLTF(1):ind.HTLTF(2),:);

Perform OFDM demodulation on the HT-LTF.

sym = wlanHTLTFDemodulate(rx,cfg);

Return OFDM information, extracting the data and pilot subcarriers.

info = wlanHTOFDMInfo('HT-LTF',cfg);
data = sym(info.DataIndices,:,:);
pilots =  sym(info.PilotIndices,:,:);

Obtain OFDM information for the HT-Data field.

Specify the channel bandwidth and guard interval duration.

cbw = 'CBW40';
gi = 'Long';

Return and display the OFDM information for the HT-Data field.

info = wlanHTOFDMInfo('HT-Data',cbw,gi);
disp(info);
                 FFTLength: 128
                  CPLength: 32
            NumSubchannels: 2
                  NumTones: 114
    ActiveFrequencyIndices: [114x1 double]
          ActiveFFTIndices: [114x1 double]
               DataIndices: [108x1 double]
              PilotIndices: [6x1 double]

Obtain OFDM information for the L-LTF for a specified value of channel bandwidth.

Specify a channel bandwidth of 40 MHz.

cbw = 'CBW40';

Return and display the OFDM information for the L-LTF.

info = wlanHTOFDMInfo('L-LTF',cbw);
disp(info);
                 FFTLength: 128
                  CPLength: [64 0]
            NumSubchannels: 2
                  NumTones: 104
    ActiveFrequencyIndices: [104x1 double]
          ActiveFFTIndices: [104x1 double]
               DataIndices: [96x1 double]
              PilotIndices: [8x1 double]

Input Arguments

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Field for which to return OFDM information, specified as one of these values.

  • 'L-LTF': demodulate the legacy long training field (L-LTF).

  • 'L-SIG': demodulate the legacy signal (L-SIG) field.

  • 'HT-SIG': demodulate the HT signal (HT-SIG) field.

  • 'HT-LTF': demodulate the HT long training field (HT-LTF).

  • 'HT-Data': demodulate the HT-Data field.

Data Types: char | string

Physical layer (PHY) format configuration, specified as a wlanHTConfig object.

Channel bandwidth, specified as one of these values.

  • 'CBW20': indicates a channel bandwidth of 20 MHz.

  • 'CBW40': indicates a channel bandwidth of 40 MHz.

Data Types: char | string

Guard interval duration, in microseconds, specified as 'Short' or 'Long'.

Data Types: double

Output Arguments

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OFDM information, returned as a structure containing the following fields.

Length of the fast Fourier transform (FFT), returned as a positive integer.

Data Types: double

Cyclic prefix length, in samples, returned as a positive integer.

Data Types: double

Number of active subcarriers, returned as a nonnegative integer.

Data Types: double

Number of 20-MHz subchannels, returned as a positive integer.

Data Types: double

Indices of active subcarriers, returned as a column vector of integers in the interval [-FFTLength/2, FFTLength/2 – 1]. Each entry of ActiveFrequencyIndices is the index of an active subcarrier such that the DC or null subcarrier is at the center of the frequency band.

Data Types: double

Indices of active subcarriers within the FFT, returned as a column vector of positive integers in the interval [1, FFTLength].

Data Types: double

Indices of data within the active subcarriers, returned as a column vector of positive integers in the interval [1, NumTones].

Data Types: double

Indices of pilots within the active subcarriers, returned as a column vector of integers in the interval [1, NumTones].

Data Types: double

Data Types: struct

Extended Capabilities

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

Introduced in R2019a