Redundancy ,Error detection and Error correction in Data communication

Redundancy

The central concept in detecting or correcting error’s is redundancy.To be able to detect or correct errors,we need to send some extra bit with our data.This redundant bits are added by the sender and removed by the receiver.These presence allows the receiver to detect or correct corrupted bits.

Error detection

Error detection is the process of verifying the received information weather it is correct or not.At the receiver end with out having any information of sent original message. In sender side some redundant bits are added to the original message based some property or message signal and in the receiver side by scanning this redundant bits.The error in the message will predicted.

Error detection is the detection of errors caused by noise or other impairment during transmission from the transmitter to receiver

There have some error detection checks / Error detection techniques -

1. Parity checking

2. Longitudinal redundancy check (LRC )

3. Checksum

4. Cycle redundancy check (CRC)

Error Correction

Error correction is the next step of error detection.Once the receiver detects the error in the message the error will be corrected by the error correcting codes . It some cases It may ask the sender to resent the data.hamming distance code is the best error correction technique used in the receiver to detect an error.

In correction,we need to know the exact number of bits that are corrupted and their location in the message.The number of the errors and size of message are important .It is much difficult then error detection.

In short, Error correction is the detection of errors and reconstruction of the original error free data.

Error correction can be done in two ways-

1) Backward Error correction

2) Forward Error correction