wlanS1GDemodulate

Demodulate fields of S1G waveform

Syntax

sym = wlanS1GDemodulate(rx,field,cfg)

sym = wlanS1GDemodulate(___,Name=Value)

Description

sym = wlanS1GDemodulate(rx,field,cfg) recovers a demodulated frequency-domain signal by orthogonal frequency-division multiplexing (OFDM) demodulating received time-domain signal rx. The function demodulates rx by using S1G transmission parameters cfg and signal field value field.

sym = wlanS1GDemodulate(___,Name=Value) specifies additional options using one or more name-value arguments in combination with the previous syntax.

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,:,:);

Demodulate S1G-Data field for OFDM Symbol Offset

Generate a WLAN waveform for an S1G transmission with the specified modulation and coding scheme (MCS).

cfg = wlanS1GConfig(MCS=7);
bits = [0;0;0;1];
waveform = wlanWaveformGenerator(bits,cfg);

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

ind = wlanFieldIndices(cfg);
rx = waveform(ind.S1GData(1):ind.S1GData(2),:);

Perform OFDM demodulation on the S1G-Data field, specifying an OFDM symbol offset of 0.

field = 'S1G-Data';
sym = wlanS1GDemodulate(rx,field,cfg,OFDMSymbolOffset=0);

Input Arguments

rx — Received time-domain signal

complex-valued matrix

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

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

• N_r is the number of receive antennas.

Data Types: double
Complex Number Support: Yes

field — Field to be demodulated

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

Field to be demodulated, specified as one of these values.

• 'S1G-LTF1' — Demodulate the first S1G long training field (S1G-LTF1).

• 'S1G-SIG' — Demodulate the S1G signaling (S1G-SIG) field.

• 'S1G-LTF2N' — Demodulate the subsequent S1G long training fields (S1G-LTF2N).

• 'S1G-SIG-A' — Demodulate the S1G signal A (S1G-SIG-A) field.

• 'S1G-SIG-B' — Demodulate the S1G signal B (S1G-SIG-B) field.

• 'S1G-Data' — Demodulate the S1G-Data field.

Data Types: char | string

cfg — PHY format configuration

wlanS1GConfig object

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

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Example: symOffset=0.5

OFDMSymbolOffset — OFDM symbol sampling offset

0.75 (default) | scalar in the interval [0, 1]

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

OversamplingFactor — Oversampling factor

1 (default) | scalar greater than 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. For more information, see FFT-Based Oversampling.

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

Output Arguments

sym — Demodulated frequency-domain signal

complex-valued array

Demodulated frequency-domain signal, returned as a complex-valued array of size N_sc-by-N_sym-by-N_r.

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

• N_sym is the number of OFDM symbols.

• N_r is the number of receive antennas.

Data Types: double
Complex Number Support: Yes

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

R2024a: FFT-based oversampling

The function now supports FFT-based oversampling. To specify an oversampling factor, use the OversamplingFactor name-value argument.