MT LDPC Encoder

Download PDF

Updated2023-02-17
4 minute(s) read

MT LDPC Encoder

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.

Inputs/Outputs

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.

input bit stream

The incoming bit stream to be mapped to LDPC symbols.

error in

Error conditions that occur before this node runs.

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

Standard Error Behavior

Default value: No error

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 value: TRUE

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.

output bit stream

Bit sequence encoded by this node.

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 ].

error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

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
$m = n \times j \div k$
)
the rate of (n,j,k) LDPC Code is
$R \geq 1 - (j \div k)$

Then

H = (\begin{matrix} 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 \end{matrix})

H = (\begin{matrix} 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 \end{matrix})

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.

LabVIEW Modulation Toolkit

Table of Contents

MT LDPC Encoder

Inputs/Outputs

parity check matrix in

input bit stream

error in

reset?

parity check matrix out

output bit stream

error out

Low-Density Parity Check (LDPC) Encoding

Log in to get a better experience