Error Detection and Correction

Introduction to Error Detection:

Error detection is a crucial aspect of computer networks to ensure data integrity. It involves identifying errors in data transmission over unreliable or noisy communication channels.

Parity Check:

A simple error detection technique where a parity bit is added to the data. This bit indicates whether the number of 1's in the data is odd or even.

Checksum:

Checksum is used to verify data integrity by calculating a value based on the sum of data units. The sender calculates the checksum and sends it along with data; the receiver recalculates it to check for errors.

Cyclic Redundancy Check (CRC):

CRC is a more robust error detection method that uses polynomial division to detect changes in raw data. It is widely used in network communications.

Hamming Code:

A method that not only detects but also corrects errors. Hamming codes can detect up to two simultaneous bit errors and correct single-bit errors.


public class ParityCheck {
    public static boolean checkParity(int[] data) {
        int parity = 0;
        for (int bit : data) {
            parity ^= bit;
        }
        return parity == 0;
    }

    public static void main(String[] args) {
        int[] data = {1, 0, 1, 1};
        System.out.println("Parity Check: " + (checkParity(data) ? "No Error" : "Error Detected"));
    }
}

Error Correction Techniques:

Error correction methods, unlike error detection, allow for the correction of errors in the data. These techniques are essential for reliable data transmission.

Forward Error Correction (FEC):

FEC involves sending redundant data along with the original data so that the receiver can correct errors without needing a retransmission.

Automatic Repeat reQuest (ARQ):

ARQ uses acknowledgments and timeouts to ensure data is received correctly. If an error is detected, the receiver requests a retransmission.


public class HammingCode {
    public static int[] generateHammingCode(int[] data) {
        // Implementation to generate Hamming Code
        // This is a placeholder for educational purposes
        return new int[]{0, 1, 1, 0, 1, 0, 0}; // Example output
    }

    public static void main(String[] args) {
        int[] data = {1, 0, 1, 1};
        int[] hammingCode = generateHammingCode(data);
        System.out.println("Hamming Code: " + Arrays.toString(hammingCode));
    }
}

Console Output:

Parity Check: No Error
Hamming Code: [0, 1, 1, 0, 1, 0, 0]