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nrOFDMModulate

Generate OFDM modulated waveform

Description

example

[waveform,info] = nrOFDMModulate(carrier,grid) generates waveform, a time-domain waveform, by performing orthogonal frequency-division multiplexing (OFDM) modulation of carrier resource array grid for carrier configuration parameters carrier. The function also returns info, a structure containing OFDM information.

[waveform,info] = nrOFDMModulate(grid,scs,initNSlot) modulates the carrier resource array with subcarrier spacing scs and initial slot number initNSlot.

example

[waveform,info] = nrOFDMModulate(grid,scs,initNSlot,'CyclicPrefix',cpl) specifies cyclic prefix length cpl.

example

[waveform,info] = nrOFDMModulate(___,Name,Value) specifies options by using one or more name-value pair arguments in addition to any combination of input arguments from the previous syntaxes.

Examples

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Generate a waveform by performing OFDM modulation of a resource array that contains sounding reference signals (SRSs). The resource array spans an entire frame.

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

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

Configure SRS parameters, setting the slot periodicity to 2 and the offset to zero.

srs = nrSRSConfig('SRSPeriod',[2 0]);

Get OFDM information for the specified carrier configuration.

info = nrOFDMInfo(carrier);

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

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

Perform OFDM modulation on the resource array for the specified carrier configuration.

[waveform,info] = nrOFDMModulate(carrier,grid);

Generate a waveform by performing OFDM modulation of a resource array that contains physical downlink shared channel (PDSCH) demodulation reference signal (DM-RS) symbols.

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.

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

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

initNSlot = carrier.NSlot;
cpl = 'extended';
[waveform,info] = nrOFDMModulate(grid,scs,initNSlot,'CyclicPrefix',cpl);
disp(info)
                   Nfft: 1024
             SampleRate: 61440000
    CyclicPrefixLengths: [1x48 double]
          SymbolLengths: [1x48 double]
              Windowing: 36
           SymbolPhases: [1x48 double]
         SymbolsPerSlot: 12
       SlotsPerSubframe: 4
          SlotsPerFrame: 40

Generate a waveform by performing OFDM modulation of a resource array that contains PDSCH DM-RS symbols.

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

carrier = nrCarrierConfig('NSizeGrid',106);

Configure PDSCH and generate the corresponding symbols and indices.

p = 4;
pdsch = nrPDSCHConfig('NumLayers',p);
sym = nrPDSCHDMRS(carrier,pdsch);
ind = nrPDSCHDMRSIndices(carrier,pdsch);

Create a carrier resource array and map the PDSCH symbols.

grid = nrResourceGrid(carrier,p,'OutputDataType','single');
grid(ind) = sym;

Generate OFDM modulated waveform, specifying the sample rate.

sr = 1e8;
[waveform,info] = nrOFDMModulate(carrier,grid,'SampleRate',sr);

Input Arguments

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Carrier configuration parameters for a specific OFDM numerology, specified as an nrCarrierConfig object. The function uses only these properties of this input.

Number of RBs in the carrier resource grid, specified as an integer from 1 to 275. The default value of 52 corresponds to the maximum number of RBs of a 10 MHz carrier with 15 kHz SCS.

Data Types: double

Subcarrier spacing in kHz, for all channels and reference signals of the carrier, specified as 15, 30, 60, 120, or 240.

Data Types: double

Slot number, specified as a nonnegative integer. You can set NSlot to a value larger than the number of slots per frame. For example, you can set this value using transmission loop counters in a MATLAB® simulation. In this case, you may have to ensure that the property value is modulo the number of slots per frame in a calling code.

Data Types: double

Cyclic prefix length, specified as one of these options.

  • '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, extended cyclic prefix length applies for only 60 kHz subcarrier spacing.

Data Types: char | string

Carrier resource array, specified as a complex-valued array of size K-by-N-by-P.

  • K is the number of subcarriers.

  • N is the number of OFDM symbols.

  • P is the number of transmit antennas.

Data Types: single | double | aveform
Complex Number Support: Yes

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

Data Types: double

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

Data Types: double

Cyclic prefix length, specified as one of these options:

  • '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.

Data Types: char | string

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example: 'CyclicPrefix','extended' specifies extended cyclic prefix length.

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

If you do not specify this input, or if you specify 'Nfft',[], the function sets a default value satisfying these conditions.

  • The value of this input is an integer power of 2.

  • The maximum occupancy is 85%.

  • The minimum value of this input is 128.

Data Types: double

Waveform sample rate, specified as the comma-separated pair consisting of 'SampleRate' and either 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 Nfft × SCS.

  • Nfft is the value of the 'Nfft' input.

  • SCS is the subcarrier spacing specified in the SubcarrierSpacing property of the config input for the first function syntax, or the scs input for the other syntaxes.

Data Types: double

Number of time-domain samples over which the function applies raised cosine windowing and overlapping of OFDM symbols, specified as the comma-separated pair consisting of 'Windowing' and either a nonnegative integer or [].

If you do not specify this input, or if you specify 'Windowing',[], the function sets this input to the maximum value E that does not impact error vector magnitude (EVM) tests, as specified in Annexes F.5.3 and F.5.4 of TS 38.101-1 [1], Annexes F.5.3 and F.5.4 of TS 38.101-2 [2], and Annexes B.5.2 and C.5.2 Annex TS 38.104 [3]. E is equal to value of floor((NCPW) × info.NfftNFFT, nominal), where NCP, W, and NFFT, nominal are the values in the table columns labeled "Cyclic prefix length", "EVM window length", and "FFT size", respectively.

Data Types: double

Carrier frequency, in Hz, specified as the comma-separated pair consisting of 'CarrierFrequency' and a nonnegative scalar. This input corresponds to f0, defined in TS 38.211 Section 5.4 [4].

Data Types: double

Output Arguments

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OFDM modulated waveform, returned as a complex-valued matrix of size T-by-P.

  • T is the number of time-domain samples in the waveform.

  • P is the number of transmit antennas.

Data Types: single | double
Complex Number Support: Yes

OFDM information, returned as a structure containing these fields.

FieldsValuesDescription
NfftPositive integerNumber of FFT points
SampleRatePositive scalarWaveform sample rate
CyclicPrefixLengths1-by-N vector of positive integers, where N is the number of OFDM symbols in a subframe.Cyclic prefix lengths of each OFDM symbol, in samples
SymbolLengths1-by-N vector of positive integersOFDM symbol lengths, in samples
WindowingPositive integerNumber of time-domain samples over which the function applies raised cosine windowing and overlapping of OFDM symbols
SymbolPhases1-by-N vector of scalars in the interval [-π, π]

Phase compensation of each OFDM symbol, in radians

The function applies this compensation during modulation to account for phase terms per OFDM symbol, as specified in TS 38.211 Section 5.4 [4]. The nrOFDMDemodulate function inverts this phase compensation during demodulation.

SymbolsPerSlotPositive integerNumber of OFDM symbols in a slot
SlotsPerSubframePositive integerNumber of slots in a 1 ms subframe
SlotsPerFramePositive integerNumber of slots in a 10 ms frame

Data Types: struct

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

Introduced in R2020b