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wlanEHTOFDMInfo

OFDM information for EHT transmission

Since R2023a

Description

example

info = wlanEHTOFDMInfo(field,cfg) returns info, a structure containing OFDM information for the input field in an extremely high-throughput (EHT) transmission parameterized by configuration object cfg.

example

info = wlanEHTOFDMInfo(field,cfg,ruNumber) specifies the resource unit (RU) or multiple resource unit (MRU) of interest, ruNumber. Use this syntax only when you want to return OFDM information for the EHT-Data field or the EHT long training field (EHT-LTF).

example

info = wlanEHTOFDMInfo(___,OversamplingFactor=osf) specifies the oversampling factor in addition to any input argument combination from the previous syntaxes. For more information about oversampling, see FFT-Based Oversampling.

Examples

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Get OFDM information from the EHT-LTF field in a non-OFDMA configuration.

Create a non-OFDMA EHT MU configuration object with three users and a 320 MHz bandwidth.

cfg = wlanEHTMUConfig("CBW320",NumUsers=3);

Display the OFDM information from the EHT-LTF field.

field = "EHT-LTF";
info = wlanEHTOFDMInfo(field,cfg);
disp(info)
                 FFTLength: 4096
                SampleRate: 320000000
                  CPLength: 1024
            NumSubchannels: 16
                  NumTones: 3984
    ActiveFrequencyIndices: [3984x1 double]
          ActiveFFTIndices: [3984x1 double]
               DataIndices: [3920x1 double]
              PilotIndices: [64x1 double]

Get OFDM information for each RU in an EHT MU configuration.

Create an OFDMA EHT MU configuration object. Set the allocation index to 43. This setting specifies a configuration with three users. Two users each have a 52-tone RU. The third user has a 106+26-tone MRU.

cfg = wlanEHTMUConfig(43);

Get the OFDM information from the EHT-Data field for the three resource units. Display the number of tones in each one.

for ruNumber = 1:numel(cfg.RU)
           info = wlanEHTOFDMInfo("EHT-Data",cfg,ruNumber);
           disp(info.NumTones)
end
    52

    52

   132

Create a non-OFDMA EHT MU configuration object with a channel bandwidth of 320 MHz.

cfg = wlanEHTMUConfig("CBW320");

Get the OFDM information from its EHT-LTF twice: once using the default settings, and once using an oversampling factor of 2.

info1 = wlanEHTOFDMInfo("EHT-LTF",cfg);
info2 = wlanEHTOFDMInfo("EHT-LTF",cfg,OversamplingFactor=2);

Display the sample rates. An oversampling factor of 2 doubles the rate.

disp(info1.SampleRate)
   320000000
disp(info2.SampleRate)
   640000000

Input Arguments

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

  • "L-LTF" — Return OFDM information for the legacy long training field (L-LTF).

  • "L-SIG" — Return OFDM information for the legacy signal (L-SIG) field.

  • "RL-SIG" — Return OFDM information for the repeated legacy signal (RL-SIG) field.

  • "U-SIG" — Return OFDM information for the universal signal (U-SIG) field.

  • "EHT-SIG" — Return OFDM information for the EHT signal (EHT-SIG) field.

  • "EHT-LTF" — Return OFDM information for the EHT long training field (EHT-LTF).

  • "EHT-Data" — Return OFDM information for the EHT-Data field.

Data Types: char | string

Physical layer (PHY) format configuration, specified as an object of type wlanEHTMUConfig, wlanEHTTBConfig, or wlanEHTRecoveryConfig.

Number of the RU or MRU of interest, specified as a positive integer. This input specifies the location of the RU or MRU in the channel. For example, consider a 20 MHz transmission with one 106+26-tone MRU, one 52+26-tone MRU, and one 26-tone RU, in order of absolute frequency. For this allocation:

  • RU 1 corresponds to the 106+26-tone MRU at the lowest absolute frequency (size 106+26, index 1).

  • RU 2 corresponds to the 52+26-tone MRU at the next lowest absolute frequency (size 52+26, index 2).

  • RU 3 corresponds to the 26-tone RU at the highest absolute frequency (size 26, index 3).

Note

  • For an OFDMA-type EHT MU PPDU, this input is required when the field input is "EHT-LTF" or "EHT-Data".

  • For a non-OFDMA-type EHT MU PPDU, this input is not required, regardless of the value of the field input.

  • For an EHT TB PPDU, this input is not required.

  • This input is not required when field is equal to "L-LTF", "L-SIG", "RL-SIG", U-SIG", or "EHT-SIG".

  • This input is not required when you specify cfg as a wlanEHTRecoveryConfig object.

Data Types: single | double

Oversampling factor, specified as a scalar greater than or equal to 1. The oversampled cyclic prefix length must be an integer number of samples.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Output Arguments

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OFDM information, returned as a structure containing these fields.

NameValuesDescriptionData Types
FFTLengthPositive integerLength of the fast Fourier transform (FFT)double
SampleRatePositive scalarSample rate of the waveformdouble
CPLengthPositive integer

Cyclic prefix length, in samples

double
NumTonesNonnegative integer

Number of active subcarriers

double
NumSubchannelsPositive integerNumber of 20 MHz subchannelsdouble
ActiveFrequencyIndicesColumn vector of integers in the interval [–FFTLength/2, (FFTLength/2 – 1)]Indices of active subcarriers. Each element of this field is the index of an active subcarrier, such that the direct current (DC) or null subcarrier is at the center of the frequency band.double
ActiveFFTIndicesColumn vector of integers in the interval [1, FFTLength]Indices of active subcarriers within the FFTdouble
DataIndicesColumn vector of integers in the interval [1, NumTones]Indices of data within the active subcarriersdouble
PilotIndicesColumn vector of integers in the interval [1, NumTones]Indices of pilots within the active subcarriersdouble

Data Types: struct

Algorithms

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FFT-Based Oversampling

An oversampled signal is a signal sampled at a frequency that is higher than the Nyquist rate. WLAN signals maximize occupied bandwidth by using small guardbands, which can pose problems for anti-imaging and anti-aliasing filters. Oversampling increases the guardband width relative to the total signal bandwidth, thereby increasing the number of samples in the signal.

This function performs oversampling by using a larger IFFT and zero pad when generating an OFDM waveform. This diagram shows the oversampling process for an OFDM waveform with NFFT subcarriers comprising Ng guardband subcarriers on either side of Nst occupied bandwidth subcarriers.

FFT-based oversampling

Extended Capabilities

Version History

Introduced in R2023a

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