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MT LDPC Encoder (G Dataflow)

Version:
    Last Modified: February 7, 2018

    Performs LDPC encoding on the input bit stream based on the parity check matrix. The parity check matrix can be generated by MT LDPC Generate Regular Parity Check Matrix, MT LDPC Generate Irregular Parity Check Matrix, or you can provide it as an input to MT LDPC Encoder.

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    parity check matrix in

    The sparse parity check matrix generated by MT LDPC Generate Regular Parity Check Matrix or MT LDPC Generate Irregular Parity Check Matrix. You can also set a parity check matrix that is not rank deficient in this parameter.

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    input bit stream

    The incoming bit stream to be mapped to LDPC symbols.

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    error in

    Error conditions that occur before this node runs.

    The node responds to this input according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Default: No error

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    reset?

    A Boolean that determines whether the internal state of the encoder is cleared.

    TRUE Clears any buffered bits from previous iterations.
    FALSE Continues encoding from the previous iteration. Any buffered bits from the previous iteration are added to the beginning of the input bit stream prior to encoding.

    Default: TRUE

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    parity check matrix out

    The preprocessed parity check matrix that is used by the encoder for encoding. You must provide this parity check matrix to the decoder.

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    output bit stream

    Bit sequence encoded by this node.

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    Note  

    The encoder places the generated parity bits at the end of the output bit stream array by default. Hence, the encoded word format is [ message bits | parity bits ].

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    error out

    Error information.

    The node produces this output according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Low-Density Parity Check (LDPC) Encoding

    Low-density parity check (LDPC) is a linear error-correcting coding scheme that uses a parity check matrix that provides only a few ones with respect to a much larger number of zeros.

    The main advantage of the parity check matrix is that it provides a performance that is almost equal to the capacity of many different channels and linear time complex algorithms for decoding. Furthermore, parity check matrices are suited for implementations that make heavy use of parallelism.

    An LDPC code is a block code that has a parity check matrix H, every row and column of which is sparse. A Regular Gallager Code is an LDPC code in which every column of H has a weight, j, and every row has a weight, k. Regular Gallager codes are constructed at random, subject to these constraints.

    For example, if
    • the number of ones in each column (j) = 3
    • the number of ones in each row (k) = 6
    • the number of columns (n) = 12
    • the number of rows (m) = 6 (because m = n × j ÷ k )
    • the rate of (n,j,k) LDPC Code is R 1 ( j ÷ k )
    Then
    H = ( 1 1 1 0 0 1 1 0 0 0 1 0 1 1 1 1 1 0 0 0 0 0 0 1 0 0 0 0 0 1 1 1 0 1 1 1 1 0 0 1 0 0 0 1 1 1 0 1 0 1 0 1 1 0 1 1 1 0 0 0 0 0 1 0 1 1 0 0 1 1 1 0 )

    If the number of ones per column or row is not constant, the code is an irregular LDPC code. Usually, irregular LDPC codes outperform regular LDPC codes.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: Not supported

    Web Server: Not supported in VIs that run in a web application


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