## How to proceed and execute Decoding Using Tanner Graph in C

Hi,

I know LDPC decoding logic but i don`t have knowledge in Data Structure. Please help me How to proceed LDPC Decoding Using Tanner Graph in C Coding? Please teach me in writing coding step by step.

In that process i have been provided with a H matrix,code word like [c1, c2, c3, c4, c5, c6] =[1 0 1 0 1 1].

The received word is r=[X 0 1 X 1 1], where X = missing bits. c1 and c4 are missing bits, i need to find missing bits using tanner graph.

In tanner graph, there are two nodes : Check Nodes and Variable Nodes
—Variable-nodes: Correspond to bits of the codeword or equivalently, to columns of the parity check matrix.
There are n v-nodes
Check-nodes: Correspond to parity check equations or equivalently, to rows of the parity check matrix. Also known as constraint nodes.
—There are m = (n-k) c-nodes.

STEPS :
c4 bit is recovered first and then c1 bit is recovered. Total 2 iterations are used.

1. Messages are passed from variable nodes to check nodes. At check nodes they are processed and the results are stored

using the constraint c3^c4^ c6=0, we calculate the value of c4.

2. Update the values at variable nodes, Messages (value of c4 ) are passed from check nodes to variable nodes

3.Updated messages are again transferred from variable nodes to check nodes.
Using constraint: c1^c2^c3^c4=0
Value of c1 is calculated
4. Values are updated at variable nodes, Message (value of c1) is passed from check nodes to variable nodes
Finally, missing bits are identified