info

Provide dimensioning information for OFDM demodulator

Syntax

S = info(obj)

Description

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

Examples

Create and Modify OFDM Demodulator

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

obj — System object to return dimensional information for

comm.OFDMDemodulator

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

Data Types: object

Output Arguments

S — Dimensions for OFDM demodulator signals

structure

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.

InputSize — Demodulator input data dimensions

column vector

Demodulator input signal dimensions, specified as a column vector. The element values are computed as [(N_CPTotal + (N_FFT×N_Sym)),N_R], based on the configuration of the input obj.

For variable definitions, see List of Variables.

Data Types: double

OutputDataSize — Dimensions of output data signal

column vector

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

For variable definitions, see List of Variables.

Data Types: double

OutputPilotSize — Dimensions of pilot output signal

column vector

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

For variable definitions, see List of Variables.

Data Types: double

More About

List of Variables

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

Variable	Description
NData	Number of data subcarriers, such that NData = NFFT − NleftG − NrightG − NDCNull − NPilot − NCustNull.
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