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OFDM Equalizer

Equalize OFDM modulated signals

  • Library:
  • Communications Toolbox / Equalizers

  • OFDM Equalizer block

Description

The OFDM Equalizer block performs frequency-domain equalization to recover OFDM modulated symbols transmitted through a channel.

This icon shows the block with all ports enabled.

OFDM Equalizer block showing optional ports.

Ports

Input

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Input signal, specified as a 3-D or 2-D array of received OFDM symbols.

  • If Data format is set to 3-D, the input signal must be specified as an NSC-by-NSymbols-by-NR array. NSC represents the number of OFDM subcarriers, NSymbols represents the number of OFDM symbols, and NR represents the number of receive antennas.

  • If Data format is set to 2-D, the input signal must be specified as an NRE-by-NR array. NRE represents the number of resource elements in an irregular subset of the OFDM subcarrier symbol grid.

Data Types: double | single
Complex Number Support: Yes

Channel estimate, specified as a 3-D array.

  • If Data format is set to 3-D, the block expects hEst to be an NSC-by-NT-by-NR or an (NSC×NSymbols)-by-NT-by-NR array.

    • If hEst is an NSC-by-NT-by-NR array, all OFDM symbols in the input signal in are equalized by the same channel estimate. NSC represents the number of OFDM subcarriers, NT represents the number of transmit antennas, and NR represents the number of receive antennas.

    • If hEst is an (NSC×NSymbols)-by-NT-by-NR array, each OFDM symbol in the input signal in is equalized by the corresponding entry in hEst. NSymbols represents the number of OFDM symbols.

  • If Data format is set to 2-D, the block expects hEst to be an NRE-by-NT-by-NR array. Each OFDM symbol in the input signal in is equalized by the corresponding entry in hEst. NRE represents the number of resource elements in an irregular subset of the OFDM subcarrier symbol grid.

Data Types: double | single
Complex Number Support: Yes

Noise variance estimate for minimum mean squared error (MMSE) equalization, specified as a nonnegative scalar.

Dependencies

The noise variance input port is used only when you set Noise variance source to Input port and Algorithm to Minimum mean squared error.

Data Types: double | single

Output

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Equalized symbols, returned as a 3-D or 2-D array.

  • If Data format is set to 3-D, the block returns an NSC-by-NSymbols-by-NT array. NSC represents the number of OFDM subcarriers, NSymbols represents the number of OFDM symbols, and NT represents the number of transmit antennas.

  • If Data format is set to 2-D, the block returns an NRE-by-NT array. NRE represents the number of resource elements in an irregular subset of the OFDM subcarrier symbol grid.

Soft channel state information, returned as a matrix with size(csi,1) = size(hEst,1) and size(csi,2) = NT = size(hEst,2). NT represents the number of transmit antennas.

Dependencies

To enable this output port, select the Output soft channel state information parameter.

Parameters

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Format of the signals, specified as 3-D or 2-D.

When this parameter is set to 3-D, OFDM subcarriers and OFDM symbols use two separate dimensions in the representation of in and out.

  • The in input must be an NSC-by-NSymbols-by-NR array.

  • The out output is returned as an NSC-by-NSymbols-by-NT array.

When this parameter is set to 2-D, OFDM subcarriers and OFDM symbols use one combined dimension in the representation of in and out.

  • The in input must be an NRE-by-NR array.

  • The out output is returned as an NRE-by-NT array.

NSC represents the number of OFDM subcarriers. NSymbols represents the number of symbols. NRE represents the number of resource elements in an irregular subset of the OFDM subcarrier symbol grid. NT represents the number of transmit antennas. NR represents the number of receive antennas.

Equalization algorithm, specified as Minimum mean squared error or Zero-forcing.

  • When this parameter is set to Minimum mean squared error, the block equalizes using the MMSE algorithm.

  • When this parameter is set to Zero-forcing, the block equalizes using the zero-forcing algorithm. When using the zero-forcing algorithm, the noiseVar port value is ignored.

Source of noise variance, specified as one of these values:

  • Input port — Specify this value to use the noiseVar input port to specify the noise variance estimate for MMSE equalization.

  • Property — Specify this value to use the Noise variance parameter to specify the noise variance estimate for MMSE equalization.

Noise variance estimate for MMSE equalization, specified as a nonnegative scalar.

Dependencies

The noise variance setting is used only when you set Noise variance source to Property and Algorithm to Minimum mean squared error.

Data Types: double | single

Select this parameter to enable output port csi containing the soft channel state information.

Type of simulation to run, specified as Interpreted execution or Code generation.

  • Interpreted execution — Simulate the model by using the MATLAB® interpreter. This option requires less startup time than the Code generation option, but the speed of subsequent simulations is slower. In this mode, you can debug the source code of the block.

  • Code generation — Simulate the model by using generated C code. The first time you run a simulation, Simulink® generates C code for the block. The C code is reused for subsequent simulations unless the model changes. This option requires additional startup time, but the speed of the subsequent simulations is faster than Interpreted execution.

Block Characteristics

Data Types

double | single

Multidimensional Signals

no

Variable-Size Signals

yes

Extended Capabilities

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

Version History

Introduced in R2022b