Error detection and correction

1. Introduction

A data error happens when the original data is not the same as that received or stored. For example if this code was sent over a channel

                          1111

and this was received

                          1011

then an error has occurred in the second bit.

Errors are caused by interference of some kind happening within the transmission channel. For example

• Network cable may encounter electrical and radio interference or have faulty shielding
• Satellite links may be corrupted by lightning giving off powerful radio interference
• Fibre optic cable - the light signal may be too weak at times
• Hard disk, there may be a surface fault corrupting certain bits
• DVD drive may have a faulty laser, causing mis-reading of the data

Error detection and correction is used to make data more reliable and accurate.

All error detection and correction methods add extra (redundant) data into the transmitted data. Clever algorithms use this extra information to work out if an error has occurred (error detection) and maybe even fix it (error correction).