wlanEHTOFDMInfo

OFDM information for EHT transmission

Since R2023a

Syntax

info = wlanEHTOFDMInfo(field,cfg)

info = wlanEHTOFDMInfo(field,cfg,ruNumber)

info = wlanEHTOFDMInfo(___,OversamplingFactor=osf)

Description

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.

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).

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

Get OFDM Information from EHT-LTF Field

Create a non-OFDMA EHT MU configuration object with three users and a 320 MHz channel 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 RUs in 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 RUs. Display the number of tones in each RU.

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

    52

    52

   132

Get OFDM Information from EHT MU Waveform Using Oversampling

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

field — Field for which to return OFDM information

"L-LTF" | "L-SIG" | "RL-SIG" | "U-SIG" | "EHT-SIG" | "EHT-LTF" | "EHT-Data"

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

cfg — PHY format configuration

wlanEHTMUConfig object | wlanEHTTBConfig object | wlanEHTRecoveryConfig object

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

ruNumber — Number of RU or MRU of interest

positive integer

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

osf — Oversampling factor

1 (default) | scalar greater than or equal to 1

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

info — OFDM information

structure

OFDM information, returned as a structure containing these fields.

Name	Values	Description	Data Types
FFTLength	Positive integer	Length of the fast Fourier transform (FFT)	double
SampleRate	Positive scalar	Sample rate of the waveform	double
CPLength	Positive integer	Cyclic prefix length, in samples	double
NumTones	Nonnegative integer	Number of active subcarriers	double
NumSubchannels	Positive integer	Number of 20 MHz subchannels	double
ActiveFrequencyIndices	Column 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
ActiveFFTIndices	Column vector of integers in the interval [1, FFTLength]	Indices of active subcarriers within the FFT	double
DataIndices	Column vector of integers in the interval [1, NumTones]	Indices of data within the active subcarriers	double
PilotIndices	Column vector of integers in the interval [1, NumTones]	Indices of pilots within the active subcarriers	double

Data Types: struct

Algorithms

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, which increases 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 N_FFT subcarriers made up of N_g guardband subcarriers on either side of N_st occupied bandwidth subcarriers.

References

[1] IEEE P802.11be/D5.0. “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. Amendment 8: Enhancements for Extremely High Throughput (EHT).” Draft Standard for Information Technology — Telecommunications and Information Exchange between Systems — Local and Metropolitan Area Networks — Specific Requirements.

Extended Capabilities

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

Version History

Introduced in R2023a

R2024b: Generate C/C++ code for EHT blind recovery

You can now generate C and C++ code using MATLAB^® Coder™ when you specify the cfg input as a wlanEHTRecoveryConfig object.

R2023b: EHT recovery support

You can specify the cfg input as a wlanEHTRecoveryConfig object.