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nrOFDMInfo

Get OFDM information

Description

example

info = nrOFDMInfo(carrier) provides dimensional information relevant to orthogonal frequency-division multiplexing (OFDM) modulation for the specified carrier configuration parameters.

info = nrOFDMInfo(nrb,scs) provides OFDM information for the specified number of resource blocks, nrb, and subcarrier spacing scs.

example

info = nrOFDMInfo(___,Name,Value) specifies options by using one or more name-value pair arguments in addition to the input arguments in any of 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);

Set carrier configuration parameters, specifying a subcarrier spacing of 60 kHz and extended cyclic prefix.

scs = 60;
cpl = 'Extended';

Set the number of resource blocks to 150.

Generate and display OFDM information.

nrb = 150;
info = nrOFDMInfo(nrb,scs,'CyclicPrefix',cpl)
info = struct with fields:
                   Nfft: 4096
             SampleRate: 245760000
    CyclicPrefixLengths: [1024 1024 1024 1024 1024 1024 1024 1024 1024 ... ]
          SymbolLengths: [5120 5120 5120 5120 5120 5120 5120 5120 5120 ... ]
              Windowing: 116
           SymbolPhases: [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ... ]
         SymbolsPerSlot: 12
       SlotsPerSubframe: 4
          SlotsPerFrame: 40

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

carrier = nrCarrierConfig('NSizeGrid',106);

Generate and display OFDM information for the specified sample rate.

sr = 1e8;
info = nrOFDMInfo(carrier,'SampleRate',sr)
info = struct with fields:
                   Nfft: 3200
             SampleRate: 100000000
    CyclicPrefixLengths: [250 225 225 225 225 225 225 250 225 225 225 ... ]
          SymbolLengths: [3450 3425 3425 3425 3425 3425 3425 3450 3425 ... ]
              Windowing: 112
           SymbolPhases: [0 0 0 0 0 0 0 0 0 0 0 0 0 0]
         SymbolsPerSlot: 14
       SlotsPerSubframe: 1
          SlotsPerFrame: 10

Input Arguments

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

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

Data Types: double

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

Data Types: double

Name-Value 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: 'SampleRate','1e9' specifies a sample rate of 1×109 Hz.

Cyclic prefix length, specified as the comma-separated pair consisting of 'CyclicPrefix' and 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 pair argument together with the carrier input.

Data Types: char | string

Number of fast Fourier transform (FFT) points, specified as the comma-separated pair consisting of 'Nfft' and 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 × NRB)/Nfft, where NRB 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

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. 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

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 TS 38.101-1 Annexes F.5.3 and F.5.4, TS 38.101-2 Annexes F.5.3 and F.5.4, and TS 38.104 Annexes B.5.2 and C.5.2. 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 real number. This input corresponds to f0, defined in TS 38.211 Section 5.4.

Data Types: double

Output Arguments

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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 numbers in the interval [-π, π]

Phase compensation of each OFDM symbol, in radians

The nrOFDMModulate 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

For more information on these fields, see the Use Custom OFDM Sample Rate and Custom FFT Size example.

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