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Error Detection Codes

 

What is an error?

A mismatched data is known as an “error”. The data can be corrupted while transitioning from the sender to the receiver. It may cause loss of important information and might be responsible for the change in the performance of the system. 

 

Types of error

There are various types of errors, namely:

  1. Single bit error: When there is a change in one bit of data, it is known as a “single-bit error”. 
  2. Multiple bit error: When there is a change in two or more bits of data, it is known as “multiple bit errors”. 
  3. Burst errors: When there is a change in a set of bits in the data sequence, it is known as “burst errors”. 

 

What are error-detecting codes?

Some redundancy codes are used to detect errors by adding to the data while it is transmitting from the sender, these codes are known as “error-detecting codes”.

There are various types of error detection, some are mentioned below:

  1. Parity Checking
  2. Cyclic Redundancy Check or CRC
  3. Longitudinal Redundancy Check or LRC
  4. CheckSum

 

Parity Checking

In Parity Checking an additional bit of data is added before transmitting the data. It is also known as “Vertical Redundancy Check” or VRC.

There are two types of parity bit:

  1. Even Parity
  2. Odd Parity

 

Cyclic Redundancy Check or CRC

A cyclic code is a linear code block where every cyclic shift of a codeword results in another codeword. The codes used for CRC are known as CRC codes and are used for error detection and encoding. 

 

Longitudinal Redundancy Check

In LRC, a block of bits is arranged in tabular format and the parity bit of each column is calculated separately. It is useful to detect burst errors and single-bit errors.

 

CheckSum

It is similar to the parity bit, the only difference being the sum of bits in the checksum is much larger, and the result is always constrained to be zero, implying that if the checksum is zero, an error is detected. 

There are five types of checksum methods:

  1. Integer addition checksum
  2. One’s complement checksum
  3. Fletcher Checksum
  4. Adler Checksum
  5. ATN Checksum 

 

Reference

Error Detection Codes