Channel coding is a signal-processing technique which makes the representation of information bits interdependent and introduces redundancy into the sequences so that noise averaging and error protection can be achieved. It originates from the development of information theory by Shannon ' in the late 1940s which showed that any channel of known characteristics has a calculable capacity for information transfer. Provided that capacity is not being exceeded, it should be possible to achieve reliable communications with an error rate which can be reduced to any desired level by increasing the length of the codes used. The passage of 50 years since Shannon's discoveries has not yielded practicable coding schemes which allow theoretical channel capacity and error rates to be achieved. There are certain recently discovered codes which appear to provide the closest approach to the Shannon performance, but mainstream practice is content to adopt more modest aims. These could include the reduction of error rates to be suitable for a particular application or to allow the extension of operations to difficult areas. A common objective would be to reduce the power requirements for acceptable error rates, since high power brings with it several expensive problems including effects induced by nonlinear power devices. In this cost-conscious age, it is unlikely that cost-effective solutions to digital communications can be achieved without coding.

Inspec keywords: channel capacity; telecommunication network reliability; signal processing; digital communication; channel coding; information theory; error detection codes

Other keywords: reliable communication; digital communication; error rate reduction; practicable coding scheme; noise averaging; Shannon theory; information bit interdependent; signal-processing technique; channel coding; error-detection strategy; channel capacity

Subjects: Codes