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.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

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, 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 N_FFT subcarriers comprising 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.