Friday, May 1, 2009

Forward Error Correction

The increasing popularity of data-intensive applications is driving the need for more accurate and faster data communication systems. Developers of data communications systems are looking ways to exploit the available bandwidth and enhance the quality of data transmission.The data sent from the source is called information bits, and the data created after error correction is called coded bits. Since the decoder only uses the information received and never requests a retransmission, the data is always moving forward, thus the name 'forward error correction.' Since FEC does not require handshaking between source and destination, it can be used for multiple simultaneous data transmission from a single source.the character that conforms to the protocol is accepted as correct. In case both characters do not conform to the protocol being used, they are rejected altogether. This result will be displayed as a blank space or an underscore.FEC protocols impose a greater bandwidth overhead than backward error correction protocols, but they are still preferred in certain transmissions as they are able to recover from errors more quickly and with significantly fewer retransmissions.

A simple data set consists of a single column of values. This appears in the form of a list. The collection of values in such a univariate data set is not a typical set (ordered list) in the mathematical sense. Rather they are called as a multiset.The values contained in a data set may be numbers or nominal data. Web browser or operating system, wants to access a datum, presumably in the permanent storage, it first checks the cache. If it finds an entry there with a tag matching that of the desired datum, it uses the datum in the entry instead of the datum in the backing store. This process is known as cache hit. On the other hand, if it does not find the datum with the desired tag, the situation is known as a cache miss. A hit ratio is the percentage of data accesses that result in cache hits.The numbers can be real numbers or integers. However, for a given variable, the values will be of the same kind. There may be a missing value for a corresponding variable, which may be indicated in a different way.