wlanHEDemodulate

Demodulate fields of HE waveform

Description

example

sym = wlanHEDemodulate(rx,field,cfg) returns demodulated frequency-domain signal sym by performing orthogonal frequency-division multiplexing (OFDM) demodulation on received time-domain signal rx parameterized by high-efficiency (HE) configuration object cfg. The function uses parameters appropriate for field, the specified signal field.

example

sym = wlanHEDemodulate(rx,field,cfg,ruNumber) returns the frequency-domain signal for the resource unit of interest, as determined by its number ruNumber. Use this syntax when specifying cfg as an HE multiuser (HE MU) configuration object to demodulate either the HE-Data field or the HE long training field (HE-LTF).

sym = wlanHEDemodulate(rx,field,cbw,hegi,ru) returns the frequency-domain signal for 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) returns the frequency-domain signal for HE-LTF type specified in ltfType. 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) returns the frequency-domain signal for the input field and channel bandwidth. To return OFDM information for any of the L-LTF, L-SIG, RL-SIG, HE-SIG-A, or HE-SIG-B fields when the PHY format configuration is unknown, use this syntax.

sym = wlanHEDemodulate(___,'OFDMSymbolOffset',symOffset) returns the frequency-domain signal for OFDM symbol sampling offset symOffset, specified as a fraction of the cyclic prefix length.

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. The size of this input must be NS-by-NR, where NS is the number of time-domain samples and NR is the number of receive antennas. 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.

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 a wlanHESUConfig object or wlanHEMUConfig object.

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: 'OFDMSymbolOffset',0.45

Data Types: double

Output Arguments

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Demodulated frequency-domain signal, returned as a complex-valued array of size sym is NSC-by-Nsym-by-NR, where:

  • 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.

Extended Capabilities

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

Introduced in R2019a