wlanS1GOFDMInfo

OFDM Information for S1G transmission

Syntax

info = wlanS1GOFDMInfo(field,cfg)

info = wlanS1GOFDMInfo(field,cfg,OversamplingFactor=osf)

Description

info = wlanS1GOFDMInfo(field,cfg) returns info, a structure containing orthogonal frequency-division multiplexing (OFDM) information for the input field of a sub-1-Ghz (S1G) transmission parameterized by configuration object cfg.

info = wlanS1GOFDMInfo(field,cfg,OversamplingFactor=osf) returns OFDM information for the specified oversampling factor. For more information about oversampling, see FFT-Based Oversampling.

Examples

Demodulate S1G-SIG Field and Get OFDM Information

Generate a WLAN waveform for an S1G transmission.

cfg = wlanS1GConfig;
bits = [1;0;0;1];
waveform = wlanWaveformGenerator(bits,cfg);

Obtain the field indices and extract the S1G-SIG field.

ind = wlanFieldIndices(cfg);
rx = waveform(ind.S1GSIG(1):ind.S1GSIG(2),:);

Perform OFDM demodulation on the S1G-SIG field.

sym = wlanS1GDemodulate(rx,'S1G-SIG',cfg);

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

info = wlanS1GOFDMInfo('S1G-SIG',cfg);
data = sym(info.DataIndices,:,:);
pilots =  sym(info.PilotIndices,:,:);

Get OFDM Information for S1G-Data Field

Get OFDM information for the S1G-Data field in a transmission with specified channel bandwidth and oversampling factor.

Create a WLAN S1G format configuration object, specifying the channel bandwidth.

cfg = wlanS1GConfig('ChannelBandwidth','CBW1');

Specify an oversampling factor.

osf = 1.5;

Return and display the OFDM information for the S1G-Data field.

info = wlanS1GOFDMInfo('S1G-Data',cfg,OversamplingFactor=osf);
disp(info)

                 FFTLength: 48
                SampleRate: 1500000
                  CPLength: 12
            NumSubchannels: 1
                  NumTones: 26
    ActiveFrequencyIndices: [26×1 double]
          ActiveFFTIndices: [26×1 double]
               DataIndices: [24×1 double]
              PilotIndices: [2×1 double]

Input Arguments

field — Field for which to return OFDM information

'S1G-LTF1' | 'S1G-SIG' | 'S1G-LTF2N' | 'S1G-SIG-A' | 'S1G-SIG-B' | 'S1G-DLTF' | 'S1G-Data'

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

• 'S1G-LTF1' – Return OFDM information for the first S1G long training field (S1G-LTF1).

• 'S1G-SIG' – Return OFDM information for the S1G signaling (S1G-SIG) field.

• 'S1G-LTF2N' – Return OFDM information for the subsequent S1G long training fields (S1G-LTF2N).

• 'S1G-SIG-A' – Return OFDM information for the S1G signal A (S1G-SIG-A) field.

• 'S1G-SIG-B' – Return OFDM information for the S1G signal B (S1G-SIG-B) field.

• 'S1G-DLTF' – Return OFDM information for the S1G beamformed LTF (D-LTF).

• 'S1G-Data' – Return OFDM information for the S1G-Data field.

Data Types: char | string

cfg — PHY format configuration

wlanS1GConfig object

Physical layer (PHY) format configuration, specified as a wlanS1GConfig object.

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.

Extended Capabilities

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

Version History

Introduced in R2019a