Error detection and correction in data communication
Error detection is the detection of errors caused by noise or
other impairments during transmission from the transmitter to
the receiver.
Error correction is the detection of errors and reconstruction of
the original error free data.
Error detection and correction are implemented at the data link
layer or the transport layer of the open system interconnection
model (OSI)
TYPES OF ERRORS
1. single bit error.
2. multiple bit error or burst error.
1. single bit error
As it name signifies- The term single bit error means that only one
bit of the given data unit (such as byte, character or packet) is
changed from 0 to 1 or from 1 to 0.
single bit error are the least likely type of error in serial data
communication.
this is because for a single bit error to occur the noise must have
duration of 1micro second which is very rare. Noise normally last for
much Longer than this.
2. Burst error (multiple bit error)
The term burst error means that two or more bit of the given date
unit have changed from 0 to 1 or from 1 to 0.
A burst error does not means that error occur in consecutive bits.
Redundancy
The central concept in detecting and correcting error
is redundancy.
To be able to detect or correct error we need to send some extra
bits with our data. These extra bits are called redundant bits.
Basically, Redundancy is a technique for detection and correction of
error in which redundant bits itself do not have any information or
data but they act as data bits.
redundant bits are added by the sender and are removed by the
receiver.
METHODS OF ERROR DETECTION
1. VRC (vertical redundancy check )
In VRC a parity bit is added to every data unit so that the total
number of 1s become even.It can detect all single bit error. It can
detect burst error only if total number of errors in the data unit is
odd.
2. LRC ( Longitudinal redundancy check )
In LRC,
block of bits are divided into rows and a redundant rows of
bits is then added to the whole block.
3. checksum
It detects all errors involving an odd number of bits as well as most
errors involving an even number of bits.
Basically the error detection method used by the higher layer
protocols is called checksum.
4. The fourth and most efficient method of error detection
is CRC that is cyclic redundancy check.
A CRC i.e. cyclic redundancy check is a non secure hash
function designed to detect accidental changes to raw computer
data and is commnly used in digital networks and storage devices
such as hard disk.
ERROR CORRECTION
Two methods of error correction are1. reverse error correction (REC).
2. Forward error correction( FEC)
In the first approach the receiver requests for the retransmission of
the code word whenever it detects an error after that the receiver
locates the error by analyzing the received code and revers the
erroneous bits.
In the second approach the code set is so designed that it is
possible for the receiver to detect and correct error as well by
itself.
DATA LINK LAYER ( REDUNDANCY ERROR DETECTION)17/06/2013In "General"
DATA LINK LAYER AND ITS ERRORS24/06/2013In "General"
FRAMES24/06/2013
https://blog.oureducation.in/error-detection-and-correction-in-data-communication/