Thus, There Are Essentially Two Aspects to Coding Theory

Elements of Coding Theory

Coding theory is studied by various scientific disciplines — such as information theory, electrical engineering,mathematics, and computer science — for the purpose of designing efficient and reliable data transmission methods. This typically involves the removal of redundancy and the correction (or detection) of errors in the transmitted data. It also includes the study of the properties of codes and their fitness for a specific application.

Thus, there are essentially two aspects to Coding theory:

1.Data compression (or, source coding)

2.Error correction (or, channel coding')

These two aspects may be studied in combination.

The first, source encoding, attempts to compress the data from a source in order to transmit it more efficiently. This practice is found every day on the Internet where the common "Zip" data compression is used to reduce the network load and make files smaller. The second, channel encoding, adds extra data bits to make the transmission of data more robust to disturbances present on the transmission channel. The ordinary user may not be aware of many applications using channel coding. A typical music CD uses theReed-Solomon code to correct for scratches and dust. In this application the transmission channel is the CD itself. Cell phones also use coding techniques to correct for the fading and noise of high frequency radio transmission. Data modems, telephone transmissions, and NASA all employ channel coding techniques to get the bits through, for example the turbo code and LDPC codes.

The hamming metric:

3-bit binary cube for finding Two example distances: 100->011 has distance 3 (red Hamming distance path); 010->111 has distance 2 (blue path)

4-bit binary hypercube for finding Hamming distance

Two example distances: 0100->1001 has distance 3 (red path); 0110->1110 has distance 1 (blue path)

In information theory, the Hamming distance between two strings of equal length is the number of positions at which the corresponding symbols are different. Put another way, it

measures the minimum number of substitutions required to change one string into the other, or the number of errors that transformed one string into the other.

Examples

The Hamming distance between:

•"toned" and "roses" is 3.

•1011101 and 1001001 is 2.

•2173896 and 2233796 is 3.