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wlanHEDemodulate

Demodulate fields of HE waveform

Description

example

sym = wlanHEDemodulate(rx,field,cfg) recovers a demodulated frequency-domain signal by orthogonal frequency-division multiplexing (OFDM) demodulating received high-efficiency (HE) time-domain signal rx. The function demodulates rx by using HE transmission parameters cfg and signal field value field.

example

sym = wlanHEDemodulate(rx,field,cfg,ruNumber) specifies the number of a resource unit. To demodulate either the HE-Data field or the HE long training field (HE-LTF), use this syntax.

sym = wlanHEDemodulate(rx,field,cbw,hegi,ru) specifies channel bandwidth cbw, guard interval hegi, and resource unit determined by the size and index specified in ru. If ru is not specified, the function returns the demodulated signal assuming a full band configuration. To demodulate the HE-Data field when the PHY format is unknown, use this syntax.

sym = wlanHEDemodulate(rx,field,cbw,hegi,ltfType,ru) specifies the HE-LTF type. If ru is not specified, wlanHEDemodulate returns the demodulated signal assuming a full band configuration. To demodulate the HE-LTF when the PHY format is unknown, use this syntax.

example

sym = wlanHEDemodulate(rx,field,cbw) recovers the frequency-domain signal for the specified field and channel bandwidth. To demodulate the L-LTF, L-SIG, RL-SIG, HE-SIG-A, or HE-SIG-B field when the PHY format configuration is unknown, use this syntax.

sym = wlanHEDemodulate(___,'OFDMSymbolOffset',symOffset) specifies the OFDM symbol sampling offset as a fraction of the cyclic prefix length in addition to any combination of arguments from the previous syntaxes.

Examples

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Perform OFDM demodulation on the HE-SIG-A field and extract the data and pilot subcarriers.

Generate a WLAN waveform for an HE SU transmission.

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

Obtain the field indices and extract the HE-SIG-A field.

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

Perform OFDM demodulation on the HE-SIG-A field.

sym = wlanHEDemodulate(rx,'HE-SIG-A',cfg);

Get the OFDM information, then extract the data and pilot subcarriers.

info = wlanHEOFDMInfo('HE-SIG-A',cfg);
data = sym(info.DataIndices,:,:);
pilots =  sym(info.PilotIndices,:,:);

Demodulate the HE-LTF for each RU in an HE MU waveform.

Create a WLAN HE-MU-format configuration object, specifying the allocation index, HE-LTF type, and guard interval.

AllocationIndex = 16;
cfg = wlanHEMUConfig(16,'HELTFType',2,'GuardInterval',1.6);

Generate a waveform for the specified information bits and format configuration object.

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

Generate field indices and extract the HE-LTF.

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

Demodulate the HE-LTF for each RU and display the size of the array containing the demodulated symbols in each case.

info = ruInfo(cfg);
allRUs = info.NumRUs;
for ruNumber = 1:allRUs
    sym = wlanHEDemodulate(rx,'HE-LTF',cfg,ruNumber);
    disp(size(sym));
end
    52     1

    52     1

   106     1

Perform OFDM demodulation on the legacy long training field (L-LTF) of a received signal, specifying a channel bandwidth of 80 MHz.

Retrieve the L-LTF from a very-high-throughput (VHT) waveform with a channel bandwidth of 80 MHz.

cbw = 'CBW80'; % Specify the channel bandwidth
rx = wlanLLTF(wlanVHTConfig('ChannelBandwidth',cbw));

Get the frequency-domain signal by demodulating the L-LTF.

sym = wlanHEDemodulate(rx,'L-LTF',cbw);

Input Arguments

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

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

  • Nr is the number of receive antennas.

Data Types: double
Complex Number Support: Yes

Field to be demodulated, 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.

  • 'RL-SIG' – Demodulate the repeated legacy signal (RL-SIG) field.

  • 'HE-SIG-A' – Demodulate the HE signal A (HE-SIG-A) field.

  • 'HE-SIG-B' – Demodulate the HE signal B (HE-SIG-B) field.

  • 'HE-LTF' – Demodulate the HE long training field (HE-LTF).

  • 'HE-Data' – Demodulate the HE-Data field.

Data Types: char | string

Physical layer (PHY) format configuration, specified as an object of type wlanHESUConfig, wlanHEMUConfig, or wlanHETBConfig.

Number of the RU of interest, specified as a positive integer. The RU number specifies the location of the RU within the channel. For example, consider an 80-MHz transmission with two 242-tone RUs and one 484-tone RU, in order of absolute frequency. For this allocation:

  • RU number 1 corresponds to the 242-tone RU in the 20-MHz subchannel at the lowest absolute frequency (size 242, index 1).

  • RU number 2 corresponds to the 242-tone RU in the 20-MHz subchannel at the next lowest absolute frequency (size 242, index 2).

  • RU number 3 corresponds to the 484-tone RU in the 40-MHz subchannel at the highest absolute frequency (size 484, index 2).

Data Types: double

Channel bandwidth, specified as one of these values.

  • 'CBW20' – Channel bandwidth of 20 MHz

  • 'CBW40' – Channel bandwidth of 40 MHz

  • 'CBW80' – Channel bandwidth of 80 MHz

  • 'CBW160' – Channel bandwidth of 160 MHz

Data Types: char | string

Guard interval duration, in microseconds, specified as 0.8, 1.6, or 3.2.

Data Types: double

HE-LTF type, specified as 1, 2, or 4.

Data Types: double

RU size and index, specified as a 1-by-2 vector of positive scalars. Specify ru in the form [size,index], where size must be 26, 52, 106, 242, 484, 996, or 1992 in accordance with the specified channel bandwidth. For example, an 80-MHz transmission has four possible 242-tone RUs (one for each 20-MHz subchannel). RU number 242-1 (size = 242 and index = 1) is the lowest absolute frequency within the 80-MHz channel. RU number 242-4 is the highest absolute frequency.

Data Types: double

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

Output Arguments

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Demodulated frequency-domain signal, returned as a complex-valued array of size Nsc-by-Nsym-by-Nr.

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

  • Nsym is the number of OFDM symbols.

  • Nr is the number of receive antennas.

Data Types: double
Complex Number Support: Yes

Extended Capabilities

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

Introduced in R2019a