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info

Provide dimensioning information for OFDM demodulator

Description

S = info(obj) returns a structure with fields that identify the input and output signal dimensions for the comm.OFDMDemodulator System object™, obj.

example

Examples

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Create an OFDM demodulator System object™ with default properties. Modify some of the properties. Inspect the object configuration by using the info object function.

ofdmDemod = comm.OFDMDemodulator
ofdmDemod = 
  comm.OFDMDemodulator with properties:

               FFTLength: 64
    NumGuardBandCarriers: [2x1 double]
         RemoveDCCarrier: false
         PilotOutputPort: false
      CyclicPrefixLength: 16
      OversamplingFactor: 1
              NumSymbols: 1
      NumReceiveAntennas: 1

info(ofdmDemod)
ans = struct with fields:
         InputSize: [80 1]
    DataOutputSize: [53 1]

Modify the number of subcarriers, symbols, and receive antennas. Also enable the pilot output.

ofdmDemod.FFTLength = 128;
ofdmDemod.PilotOutputPort = 1;
ofdmDemod.NumSymbols = 2;
ofdmDemod.NumReceiveAntennas = 2;

Verify that the number of subcarriers and the number of symbols changed. Reinspect the input and output signal dimensions by using the info object function. Notice the addition of the pilot output dimensions to the information structure. because the number of receive antennas is greater than 1, the data and pilot output dimensions are 3D arrays rather than matrices.

ofdmDemod
ofdmDemod = 
  comm.OFDMDemodulator with properties:

               FFTLength: 128
    NumGuardBandCarriers: [2x1 double]
         RemoveDCCarrier: false
         PilotOutputPort: true
     PilotCarrierIndices: [4x1 double]
      CyclicPrefixLength: 16
      OversamplingFactor: 1
              NumSymbols: 2
      NumReceiveAntennas: 2

info(ofdmDemod)
ans = struct with fields:
          InputSize: [288 2]
     DataOutputSize: [113 2 2]
    PilotOutputSize: [4 2 2]

Input Arguments

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System object to return dimensional information for, specified as a comm.OFDMDemodulator System object.

Data Types: object

Output Arguments

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Dimensions for OFDM demodulator signals, returned as a structure with fields that identify the dimensions of the input and output signals for the OFDM demodulator object, obj.

Demodulator input signal dimensions, specified as a column vector. The element values are computed as [(NCPTotal + (NFFT×NSym)),NR], based on the configuration of the input obj.

For variable definitions, see List of Variables.

Data Types: double

Dimensions of output data signal, specified as a column vector. The element values are computed as [NData,NSym,NR], based on the configuration of the input obj.

For variable definitions, see List of Variables.

Data Types: double

Dimensions of the pilot output signal, specified as a column vector. The element values are computed as [NPilot,NSym,NR], based on the configuration of the input obj.

For variable definitions, see List of Variables.

Data Types: double

More About

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List of Variables

These variables describe the dimensions of the input and output signals for the comm.OFDMDemodulator System object.

VariableDescription

NData

Number of data subcarriers, such that NData = NFFTNleftGNrightGNDCNullNPilotNCustNull.

NFFT

Number of subcarriers, obj.FFTLength.

NleftG and NrightG

Left and right guard bands specified by obj.NumGuardBandCarriers.

NDCNull

Number of DC null subcarriers specified as either 0 or 1, obj.InsertDCNull.

NPilot

Number of pilot subcarriers.

  • When you set obj.PilotOutputPort to 1, NPilot = size(obj.PilotCarrierIndices,1).

  • When you set obj.PilotOutputPort to 0,

    NPilot = 0 for the calculation of NData.

.

NCustNull

Number of subcarriers used for custom nulls. This variable applies only when the obj.PilotCarrierIndices is a 3D array.

NSym

Number of symbols, obj.NumSymbols.

NR

Number of receive antennas, obj.NumReceiveAntennnas.

NCPTotal

Cyclic prefix length over all the symbols.

  • NCP represents the cyclic prefix length as determined by obj.CyclicPrefixLength.

  • When obj.CyclicPrefixLength is a scalar, NCPTotal = NCP × NSym.

  • When obj.CyclicPrefixLength is a row vector, NCPTotal = ∑ NCP.

Version History

Introduced in R2014a

See Also

Objects

Functions