In the past days I've created a LDPC Block Code Simulator in Matlab. It is possible to enter the parity matrix H, the information sequence D which is encoded into codeword C and then add Gaussian Noise of a chosen variance which simulates the transmission channel charcteristics.

The simulator then calculates the original codeword and enables user to switch between the steps of the iterative decoding process. Each step displays the current message values that are passed between symbol and parity nodes and the next step operation.

Below are the screenshots of three steps. In this example H is 4 x 8 parity-check matrix ([1 0 1 0 1 0 0 0; 0 0 0 1 0 1 0 0; 1 0 0 1 0 0 1 0; 0 1 1 0 0 0 0 1]). The information sequence D ([1 0 1 1]) is encoded into codeword C (1 0 1 1 0 1 0 1). The original unipolar codeword is transformed to bipolar code (1 is transformed to -1 and 0 is transformed to 1) and the noise of variance 0.5 is added to the transformed code which results Y (-1.0371 0.12971 -1.1976 -1.808 1.3784 -1.3998 1.0451 -1.2452), the simulated received sequence. After 5 steps the algorithm determines the codeword C' (1 0 1 1 0 1 0 1) which is equal to the original codeword.

The simulator then calculates the original codeword and enables user to switch between the steps of the iterative decoding process. Each step displays the current message values that are passed between symbol and parity nodes and the next step operation.

Below are the screenshots of three steps. In this example H is 4 x 8 parity-check matrix ([1 0 1 0 1 0 0 0; 0 0 0 1 0 1 0 0; 1 0 0 1 0 0 1 0; 0 1 1 0 0 0 0 1]). The information sequence D ([1 0 1 1]) is encoded into codeword C (1 0 1 1 0 1 0 1). The original unipolar codeword is transformed to bipolar code (1 is transformed to -1 and 0 is transformed to 1) and the noise of variance 0.5 is added to the transformed code which results Y (-1.0371 0.12971 -1.1976 -1.808 1.3784 -1.3998 1.0451 -1.2452), the simulated received sequence. After 5 steps the algorithm determines the codeword C' (1 0 1 1 0 1 0 1) which is equal to the original codeword.

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