nrOFDMDemodulate

R2026b

Demodulate OFDM waveform

Syntax

grid = nrOFDMDemodulate(carrier,waveform)

grid = nrOFDMDemodulate(waveform,nrb,scs,initialNSlot)

grid = nrOFDMDemodulate(___,Name=Value)

Description

grid = nrOFDMDemodulate(carrier,waveform) recovers a carrier resource array by demodulating waveform, an OFDM modulated waveform, for carrier configuration parameters carrier.

example

grid = nrOFDMDemodulate(waveform,nrb,scs,initialNSlot) demodulates waveform for nrb, the specified number of resource blocks, subcarrier spacing scs, and initial slot number initialNSlot.

grid = nrOFDMDemodulate(___,Name=Value) specifies options by using one or more name-value arguments in addition to the input arguments in any of the previous syntaxes. For example, CyclicPrefixFraction=0.75 specifies the start location for demodulation relative to the cyclic prefix length.

example

Examples

collapse all

Demodulate OFDM Waveform

Open Live Script

Recover a transmitted carrier resource array by demodulating an OFDM waveform.

Set carrier configuration parameters, specifying 106 resource blocks (RBs) in the carrier resource array.

carrier = nrCarrierConfig(NSizeGrid=106);

Generate physical downlink shared channel (PDSCH) demodulation reference signal (DM-RS) symbols and indices.

p = 2;
pdsch = nrPDSCHConfig(NumLayers=p);
sym = nrPDSCHDMRS(carrier,pdsch);
ind = nrPDSCHDMRSIndices(carrier,pdsch);

Create a carrier resource array containing the PDSCH DM-RS symbols.

txGrid = nrResourceGrid(carrier,p);
txGrid(ind) = sym;

Generate OFDM modulated waveform.

[txWaveform,~] = nrOFDMModulate(carrier,txGrid);

Pass the waveform through a simple 2-by-1 channel.

H = [0.6; 0.4];
waveform = txWaveform*H;

Recover the carrier resource array by demodulating the received OFDM waveform.

grid = nrOFDMDemodulate(carrier,waveform);

Demodulate OFDM Waveform with Extended Cyclic Prefix

Open Live Script

Recover a resource array that contains PDSCH DM-RS symbols by demodulating an OFDM waveform.

Set carrier configuration parameters, specifying a subcarrier spacing of 60 kHz.

scs = 60;
carrier = nrCarrierConfig(SubcarrierSpacing=scs);

Generate PDSCH DM-RS symbols and indices.

p = 2;
pdsch = nrPDSCHConfig(NumLayers=p);
sym = nrPDSCHDMRS(carrier,pdsch);
ind = nrPDSCHDMRSIndices(carrier,pdsch);

Create a carrier resource array containing the PDSCH DM-RS symbols.

txGrid = nrResourceGrid(carrier,p);
txGrid(ind) = sym;

Generate an OFDM modulated waveform, specifying the subcarrier spacing, initial slot number, and cyclic prefix length.

initialNSlot = carrier.NSlot;
cpl = 'extended';
[txWaveform,info] = nrOFDMModulate(txGrid,scs,initialNSlot,CyclicPrefix=cpl);

Pass the waveform through a simple 2-by-1 channel.

H = [0.9; 0.95];
waveform = txWaveform*H;

Recover the carrier resource array by demodulating the received OFDM waveform.

nrb = carrier.NSizeGrid;
grid = nrOFDMDemodulate(waveform,nrb,scs,initialNSlot,CyclicPrefix=cpl);

Demodulate OFDM Waveform with Specified Sample Rate

Open Live Script

Recover a transmitted resource array that contains sounding reference signals (SRSs) and spans an entire frame by demodulating an OFDM waveform.

Set carrier configuration parameters, specifying a subcarrier spacing of 30 kHz and 24 resource blocks in the carrier resource array.

carrier = nrCarrierConfig(SubcarrierSpacing=30,NSizeGrid=24);

Configure SRS parameters, setting the slot periodicity and offset.

srs = nrSRSConfig(SRSPeriod=[4 0]);

Get OFDM information for the specified carrier configuration.

info = nrOFDMInfo(carrier);

Produce the frame resource array by creating and concatenating slot resource arrays.

frameGrid = [];
for nslot = 0:(info.SlotsPerFrame - 1)
    carrier.NSlot = nslot;
    slotGrid = nrResourceGrid(carrier);
    ind = nrSRSIndices(carrier,srs);
    sym = nrSRS(carrier,srs);
    slotGrid(ind) = sym;
    frameGrid = [frameGrid slotGrid];
end

Generate the OFDM modulated waveform.

[txWaveform,~] = nrOFDMModulate(carrier,frameGrid);

Pass the waveform through a simple channel.

H = 0.86;
waveform = txWaveform*H;

Recover the carrier resource array by demodulating the received OFDM waveform, specifying the sample rate.

sr = info.SampleRate;
grid = nrOFDMDemodulate(carrier,waveform,SampleRate=sr);

Input Arguments

collapse all

`carrier` — Carrier configuration parameters
`nrCarrierConfig` object

Carrier configuration parameters for a specific OFDM numerology, specified as an nrCarrierConfig object. Only these object properties are relevant for this function.

`waveform` — OFDM modulated waveform
complex-valued matrix

OFDM modulated waveform, specified as a complex-valued matrix of size T-by-R.

T is the number of time-domain samples in the waveform.
R is the number of receive antennas.

Data Types: double
Complex Number Support: Yes

`nrb` — Number of resource blocks
integer from 1 to 275

Number of resource blocks, specified as an integer from 1 to 275.

Data Types: double

`scs` — Subcarrier spacing in kHz
`15` | `30` | `60` | `120` | `240` | `480` | `960`

Subcarrier spacing in kHz, specified as 15, 30, 60, 120, 240, 480, or 960.

Data Types: double

`initialNSlot` — Initial slot number
nonnegative integer

Initial slot number, in 0-based form, specified as a nonnegative integer. The function selects the appropriate cyclic prefix lengths for OFDM demodulation by using the value of initialNSlot mod S, where S is the number of slots per subframe.

Data Types: double

Name-Value Arguments

collapse all

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: CyclicPrefixFraction=0.75 specifies the start location for demodulation relative to the cyclic prefix length.

`CyclicPrefix` — Cyclic prefix length
`'normal'` (default) | `'extended'`

Cyclic prefix length, specified as one of these values:

'normal' — Use this value to specify normal cyclic prefix. This option corresponds to 14 OFDM symbols in a slot.
'extended' — Use this value to specify extended cyclic prefix. This option corresponds to 12 OFDM symbols in a slot. For the numerologies specified in TS 38.211 Section 4.2, the extended cyclic prefix length only applies to 60 kHz subcarrier spacing.

Note

If you specify the carrier input, use the CyclicPrefix property of the carrier input to specify the cyclic prefix length. You cannot use this name-value argument together with the carrier input.

Data Types: char | string

`Nfft` — Number of FFT points
integer greater than 127 (default depends on other input values) | `[]`

Number of fast Fourier transform (FFT) points, specified as a nonnegative integer greater than 127 or []. The value you specify must result in integer-valued cyclic prefix lengths and a maximum occupancy of 100%. The occupancy is defined as the value of (12 × N_RB)/Nfft, where N_RB is the number of resource blocks.

If you do not specify this input, or if you specify Nfft=[], the function sets an integer value greater than 127 as a default value for this input. The actual default value depends on other input values.

If you do not specify the SampleRate input, or if you specify SampleRate=[], the function sets Nfft satisfying these conditions.
- Nfft is an integer power of 2.
- Nfft results in a maximum occupancy of 85%.
If you specify the SampleRate input, the function sets Nfft satisfying these conditions.
- Nfft results in integer-valued cyclic prefix lengths.
- Nfft maximises the value of gcd (Nfft × SCS, SampleRate), where SCS is specified by the carrier.SubcarrierSpacing property or the scs input.

For more information, see Configure OFDM Sample Rate and FFT Size.

Data Types: double

`SampleRate` — Waveform sample rate
positive scalar (default depends on other input values) | `[]`

Waveform sample rate, specified as a positive scalar or [].

If you do not specify this input, or if you specify SampleRate=[], then the function sets this input to the value of N_fft × SCS.

N_fft is the value of the Nfft input.
SCS is the subcarrier spacing. Depending on the function syntax you use, SCS is specified by the carrier.SubcarrierSpacing property or the scs input.

For more information, see Configure OFDM Sample Rate and FFT Size.

Data Types: double

`CarrierFrequency` — Carrier frequency in Hz
`0` (default) | real number

Carrier frequency in Hz, specified as a real number. This input corresponds to f₀, defined in TS 38.211 Section 5.4.

Data Types: double

`CyclicPrefixFraction` — FFT window position within cyclic prefix
`0.5` (default) | scalar in the interval [0, 1]

Fast Fourier transform (FFT) window position within the cyclic prefix, 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.

Data Types: double

Output Arguments

collapse all

`grid` — Carrier resource array
complex-valued array

Carrier resource array, returned as a complex-valued array of size K-by-L-by-R.

K is the number of subcarriers.
L is the number of OFDM symbols.
R is the number of receive antennas.

Data Types: double
Complex Number Support: Yes

References

[1] 3GPP TS 38.101-1. “NR; User Equipment (UE) radio transmission and reception; Part 1: Range 1 Standalone.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.

[2] 3GPP TS 38.101-2. “NR; User Equipment (UE) radio transmission and reception; Part 2: Range 2 Standalone.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.

[3] 3GPP TS 38.104. “NR; Base Station (BS) radio transmission and reception.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.

[4] 3GPP TS 38.211. “NR; Physical channels and modulation.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.

Extended Capabilities

expand all

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

Usage notes and limitations:

The SampleRate name-value argument must be compile-time constant for code generation. For example, when you call the function with SampleRate=15.36e6, include {coder.Constant("SampleRate"),coder.Constant(15.36e6)} in the -args value of the codegen function. For more information, see the coder.Constant (MATLAB Coder) class.
If you specify the SampleRate name-value argument, the nrb, scs input arguments and the Nfft name-value argument must also be compile-time constants. For example, include also {coder.Constant(nrb)} and {coder.Constant(scs)} in the -args value of the codegen function.
The SampleRate name-value argument cannot be used together with the carrier input.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Refer to the usage notes and limitations in the C/C++ Code Generation section. The same usage notes and limitations apply to GPU code generation.

GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™. (since R2024a)

The nrOFDMDemodulate function fully supports GPU arrays. To run the function on a GPU, specify the input data as a gpuArray (Parallel Computing Toolbox). For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Version History

Introduced in R2020b

expand all

R2024a: GPU array support

The nrOFDMDemodulate function now supports GPU arrays. For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

R2023a: Subcarrier spacing for FR2-2

The function now supports 480 kHz and 960 kHz subcarrier spacings, as defined in TS 38.211 Sections 4.2 and 4.3.

R2023a: C/C++ code generation updates

For C/C++ code generation, the limitation to specify CyclicPrefix, Windowing, CarrierFrequency, CyclicPrefixFraction, or Nfft name-value arguments as compile-time constants has been removed. However, if you specify the SampleRate name-value argument, the Nfft name-value argument must still be compile-time constant for code generation.

nrOFDMDemodulate

Syntax

Description

Examples

Demodulate OFDM Waveform

Demodulate OFDM Waveform with Extended Cyclic Prefix

Demodulate OFDM Waveform with Specified Sample Rate

Input Arguments

`carrier` — Carrier configuration parameters
`nrCarrierConfig` object

`waveform` — OFDM modulated waveform
complex-valued matrix

`nrb` — Number of resource blocks
integer from 1 to 275

`scs` — Subcarrier spacing in kHz
`15` | `30` | `60` | `120` | `240` | `480` | `960`

`initialNSlot` — Initial slot number
nonnegative integer

Name-Value Arguments

`CyclicPrefix` — Cyclic prefix length
`'normal'` (default) | `'extended'`

`Nfft` — Number of FFT points
integer greater than 127 (default depends on other input values) | `[]`

`SampleRate` — Waveform sample rate
positive scalar (default depends on other input values) | `[]`

`CarrierFrequency` — Carrier frequency in Hz
`0` (default) | real number

`CyclicPrefixFraction` — FFT window position within cyclic prefix
`0.5` (default) | scalar in the interval [0, 1]

Output Arguments

`grid` — Carrier resource array
complex-valued array

References

Extended Capabilities

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

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™. (since R2024a)

Version History

R2024a: GPU array support

R2023a: Subcarrier spacing for FR2-2

R2023a: C/C++ code generation updates

See Also

Functions

Objects

Topics

nrOFDMDemodulate

Syntax

Description

Examples

Demodulate OFDM Waveform

Demodulate OFDM Waveform with Extended Cyclic Prefix

Demodulate OFDM Waveform with Specified Sample Rate

Input Arguments

carrier — Carrier configuration parameters nrCarrierConfig object

waveform — OFDM modulated waveform complex-valued matrix

nrb — Number of resource blocks integer from 1 to 275

scs — Subcarrier spacing in kHz 15 | 30 | 60 | 120 | 240 | 480 | 960

initialNSlot — Initial slot number nonnegative integer

Name-Value Arguments

CyclicPrefix — Cyclic prefix length 'normal' (default) | 'extended'

Nfft — Number of FFT points integer greater than 127 (default depends on other input values) | []

SampleRate — Waveform sample rate positive scalar (default depends on other input values) | []

CarrierFrequency — Carrier frequency in Hz 0 (default) | real number

CyclicPrefixFraction — FFT window position within cyclic prefix 0.5 (default) | scalar in the interval [0, 1]

Output Arguments

grid — Carrier resource array complex-valued array

References

Extended Capabilities

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

GPU Code Generation Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

GPU Arrays Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™. (since R2024a)

Version History

R2024a: GPU array support

R2023a: Subcarrier spacing for FR2-2

R2023a: C/C++ code generation updates

See Also

Functions

Objects

Topics

`carrier` — Carrier configuration parameters
`nrCarrierConfig` object

`waveform` — OFDM modulated waveform
complex-valued matrix

`nrb` — Number of resource blocks
integer from 1 to 275

`scs` — Subcarrier spacing in kHz
`15` | `30` | `60` | `120` | `240` | `480` | `960`

`initialNSlot` — Initial slot number
nonnegative integer

`CyclicPrefix` — Cyclic prefix length
`'normal'` (default) | `'extended'`

`Nfft` — Number of FFT points
integer greater than 127 (default depends on other input values) | `[]`

`SampleRate` — Waveform sample rate
positive scalar (default depends on other input values) | `[]`

`CarrierFrequency` — Carrier frequency in Hz
`0` (default) | real number

`CyclicPrefixFraction` — FFT window position within cyclic prefix
`0.5` (default) | scalar in the interval [0, 1]

`grid` — Carrier resource array
complex-valued array

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

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™. (since R2024a)