Network, Computer and Programming Resources

Network - 4B/5B Encoding

4B/5B encoding is a data-translation scheme that serves as a preliminary to signal encoding in FDDI (Fiber Distributed Data Interface) networks. In 4B/5B, every group of four bits is represented as a five-bit symbol. This symbol is associated with a bit pattern that is then encoded using a standard signalencoding method, usually NRZI (non-return to zero inverted). This preprocessing makes the subsequent electrical encoding 80 percent efficient. For 4 5B/6B Encoding example, using 4B/5B encoding, you can achieve a 100 megabit per second (Mbps) transmission rate with a clock speed of only 125 megahertz (MHz). In contrast, the Manchester signalencoding method, which is used in Ethernet and other types of networks, is only 50 percent efficient. For example, to achieve a 100 Mbps rate with Manchester encoding, you need a 200 MHz clock speed.