- This post gives an idea on how to implement Hamming Code. Hamming code pattern is mainly used for detection of errors in bits.

## Objectives:

- The main objective is, detection of single bit error, burst error and to correct by using the suitable methodology (by hamming distance concept).
- The purpose of this project is to overcome unreliable transmission of data during the transmission from the encoder to the decoder.
- It involves block coding, finding the hamming distance between to existing code words, redundancy, error correction, parity check code.

## Description:

The theory of error detecting and correcting codes is that branch of engineering and mathematics which deals with the reliable transmission and storage of data. Information media are not 100% reliable in practice, in the sense that noise (any form of interference) frequently causes data to be distorted. To deal with this undesirable but inevitable situation, self-correcting codes are constructed by combining data bits with a number of redundant check-bits, which together are referred to as code words. By adding a single bit (as in Parity Checking) along with a given number of data-bits, half of the possible code words become valid and half invalid. This is referred to as a code that has Hamming Distance 2 (two single bit flips are required to get from one calid code to another). This particular approach, using Hamming Distance, is the minimum requirement for self-error correction and is commonly referred to as a Hamming Code.

## Preliminaries:

a. **Hamming distance** H(a,b) = #number of bit positions in which a differs from b, i.e., the number of 1’s in an XOR. Hamming distance of a code is the minimum over all pairs of distinct code words of the Hamming distance between them, i.e.,

H(code) = min {H(a,b) | a<>b and a, b in code}

b. **Error correction** – enough redundancy is transmitted in the code that errors can be corrected by the receiver without retransmission.

c. **Error detection** is the detection of errors caused by noise or other impairments during transmission from the transmitter to the receiver.

d. **d-bit error detection** requires a code with Hamming distance (d+1).

**d-bit error correction** requires a code with Hamming distance (2d+1).

## Tools Required:

- Encoder.
- Decoder.
- cyclic redundancy check (CRC) or polynomial code checksum.
- linear block codes.
- Two single bit Flip-Flop.

## Future Scope:

In the field of artificial intelligence, where there is a need to search through large state spaces, there is the notion of using evaluation functions to heuristically search a large space in a hill climbing or the best-first search fashion. Since Hamming distance is an easy-to-define metric, it is used to search the state space for design flaws.

Hamming code is an easy and efficient technique, which can only detect and correct a single bit error. However. it can also be used to detect a burst error (**A burst error means that 2 or more bits in the data unit have changed**), but by applying the different technique.

The structure of the encoder and decoder for a Hamming code

Suggested Read:

#### Following is the code in C language to implement hamming code:

Program to implement 7-bit hamming code:

#include<stdio.h> void main() { int data[10]; int dataatrec[10],c,c1,c2,c3,i; printf(“Enter 4 bits of data one by one\n”); scanf(“%d”,&data[0]); scanf(“%d”,&data[1]); scanf(“%d”,&data[2]); scanf(“%d”,&data[4]); data[6]=data[0]^data[2]^data[4]; data[5]=data[0]^data[1]^data[4]; data[3]=data[0]^data[1]^data[2]; printf(“\nEncoded data is\n”); for(i=0;i<7;i++) printf("%d",data[i]); printf("\n\nEnter received data bits one by one\n"); for(i=0;i<7;i++) scanf("%d",&dataatrec[i]); c1= dataatrec[6]^dataatrec[4]^dataatrec[2]^dataatrec[0]; c2= dataatrec[5]^dataatrec[4]^dataatrec[1]^dataatrec[0]; c3= dataatrec[3]^dataatrec[2]^dataatrec[1]^dataatrec[0]; c=c3*4+c2*2+c1 ; if(c==0 && dataatrec[6]==data[6] && dataatrec[5]==data[5] && dataatrec[3]==data[3] ) { printf("\nNo error while transmission of data\n"); } else { printf("\nError on position %d",c); printf("\nData sent : "); for(i=0;i<7;i++) printf("%d",data[i]); printf("\nData received : "); for(i=0;i<7;i++) printf("%d",dataatrec[i]); printf("\nCorrect message is\n"); if(dataatrec[7-c]==0) dataatrec[7-c]=1; else dataatrec[7-c]=0; for (i=0;i<7;i++) { printf("%d",data[i]); } } }

//HAMMING CODE for error detection and correction #include<stdio.h> int main() { int a[4],b[4],r[3], s[3],i,q[3]; printf("\nenter 4 bit data word:\n"); for(i=3;i>=0;i--) { scanf("%d",&a[i]); } r[0]=(a[2]+a[1]+a[0])%2; r[1]=(a[2]+a[1]+a[3])%2; r[2]=(a[0]+a[1]+a[3])%2; printf("\n\nthe 7bit hamming code word: \n"); for(i=3;i>=0;i--) { printf("%d\t",a[i]); } for(i=2;i>=0;i--) { printf("%d\t",r[i]); } printf("\n"); printf("\nenter the 4bit recieved word: "); for(i=3;i>=0;i--) scanf("%d",&b[i]); //calculating syndrome bits s[0]= (b[2]+b[1]+b[0]+r[0])%2; s[1]= (b[3]+b[2]+b[1]+r[1])%2; s[2]= (b[0]+b[1]+b[3]+r[2])%2; printf("\nsyndrome is: \n"); for(i=2; i>=0;i--) { printf("%d",s[i]); } if((s[2]==0) && (s[1]==0) && (s[0]==0)) printf("\n RECIEVED WORD IS ERROR FREE\n"); if((s[2]==1) && (s[1]==0) && (s[0]==1)) printf("\nrecieved word is error with error in 1bit(b0) position from right\n"); if((s[2]==1) && (s[1]==1) && (s[0]==1)) printf("\nrecieved word is error with error in 2bit(b1) position from right\n"); if((s[2]==0) && (s[1]==1) && (s[0]==1)) printf("\nrecieved word is error with error in 3bit(b2) position from right\n"); if((s[2]==1) && (s[1]==1) && (s[0]==0)) printf("\nrecieved word is error with error in 4bit(b3) position from right\n"); return(1); } //End of Hamming code program

using this formula 2^r>=m+r+1 then create program

This is correct code for 7bit hamming code please refer this:——–

#include

void main() {

int data[10];

int dataatrec[10],c,c1,c2,c3,i;

printf(“Enter 4 bits of data one by one\n”);

scanf(“%d”,&data[0]);

scanf(“%d”,&data[1]);

scanf(“%d”,&data[2]);

scanf(“%d”,&data[4]);

data[6]=data[0]^data[2]^data[4];

data[5]=data[0]^data[1]^data[4];

data[3]=data[0]^data[1]^data[2];

printf(“\nEncoded data is\n”);

for(i=0;i<7;i++)

printf("%d",data[i]);

printf("\n\nEnter received data bits one by one\n");

for(i=0;i<7;i++)

scanf("%d",&dataatrec[i]);

c1=dataatrec[6]^dataatrec[4]^dataatrec[2]^dataatrec[0];

c2=dataatrec[5]^dataatrec[4]^dataatrec[1]^dataatrec[0];

c3=dataatrec[3]^dataatrec[2]^dataatrec[1]^dataatrec[0];

c=c3*4+c2*2+c1 ;

if(c==0 && dataatrec[6]==data[6] && dataatrec[5]==data[5] && dataatrec[3]==data[3] ) {

printf("\nNo error while transmission of data\n");

}

else {

printf("\nError on position %d",c);

printf("\nData sent : ");

for(i=0;i<7;i++)

printf("%d",data[i]);

printf("\nData received : ");

for(i=0;i<7;i++)

printf("%d",dataatrec[i]);

printf("\nCorrect message is\n");

if(dataatrec[7-c]==0)

dataatrec[7-c]=1;

else

dataatrec[7-c]=0;

for (i=0;i<7;i++) {

printf("%d",data[i]);

}

}

}

Thanks for the code Kedar. Is it tested one?

How this error can be implemented as application level in project

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