Data Error Detection and Correction

Error Detection in Data Transmission

• The central concept in detecting or correcting errors in data transmission is to add redundant bits to the data being transmitted.

Error Detection Layer

• Error detection is performed at the data link layer in data transmission.

Redundant Bits

• The redundant bits added by the sender during data transmission are removed at the receiver's end.

Data Link Layer

• A Frame Check Sequence (FCS) or a Cyclic Redundancy Check (CRC) is inserted into a frame of data at the data link layer for error detection.

Causes of Errors

• Errors during data transmission can be caused by noise, attenuation, or interference.

Parity Check

• The purpose of adding parity bits to each character in Parity Check is to enable the receiver to detect single-bit errors.
• In Parity Check, a parity bit is added to each character to make the total number of 1-bits either even (even parity) or odd (odd parity).

Two-Dimensional Parity

• The Two-Dimensional Parity method increases the likelihood of detecting burst errors by treating the data as a two-dimensional array.

Checksum

• A checksum in the context of error detection in data transmission is a numerical value computed from the data being transmitted.
• The recipient can then compute the checksum again and compare it with the transmitted checksum to detect errors.

Cyclic Redundancy Checksum (CRC)

• The Cyclic Redundancy Checksum method works by treating the data as a polynomial and dividing it by a generating polynomial to produce a remainder (CRC).
• The remainder is appended to the data and transmitted along with the data.

Error-Detection Capability

• The Cyclic Redundancy Checksum method is capable of detecting all single-bit errors, all double-bit errors, and most burst errors.

Parity Bit

• The Parity Check method adds a parity bit to each character for error detection.

Polynomial Method

• The Cyclic Redundancy Checksum method treats the packet of data to be transmitted as a large polynomial.

Even Parity

• Adding 0 or 1 to the string in even parity results in an even number of 1-bits.

Two-Dimensional Array

• The data is organized as a two-dimensional array in the Two-Dimensional Parity method.

Arithmetic Checksum

• In the Arithmetic Checksum method, the sum of the data is computed and added to the end of the message.