Multiplexing or muxing is the process of allowing more than one signal to travel at the same time on a single communication channel. A mux or multiplexer facilitates the process of having more than one input signal shared between devices. Different networking protocols use multiplexing and demultiplexing services. The transport layer facilitates these services in the OSI model. In other words. It allows the transmission of more data in a smaller bandwidth. The TCP and UDP layers perform multiplexing and demultiplexing by using special fields in segment headers. These fields are part of the source and destination port number field.
There are two main types of services in multiplexing and demultiplexing, viz. Connectionless and Connection-oriented.
Types of Multiplexing
Depending on the way bandwidth divides, the techniques used for multiplexing are:
Time-division multiplexing
A single channel transmits signals in different time slots. Time division multiplexing is a type of digital multiplexing as the allocation is done using digital channels. The applications include use in Public Switched Telephone Networks (PSTN) and SONET or Synchronous Optical Networking. Telegraphs and wired telephones were one of its first implementations. Modern applications include fiber optic channels, cellular radios, and satellite communication systems.
Wavelength division multiplexing
Like frequency-division multiplexing, consolidated data transmits at various wavelengths on the same channel. Telecom channels use it for efficiency instead of spreading more fiber optic cables. Another application is in data centers for higher data traffic and scalability.
Statistical or frequency division multiplexing
Cell phones, satellite communication, radio broadcasting, cable television, etc. find large-scale implementation of frequency-division multiplexing. Orthogonal Frequency-Division Multiple Access (OFDMA)is an implementation that uses both time and frequency division. Wireless LAN or WLAN uses OFDMA for its implementation.
With a few more sub-variations to them. For example, time division can further divide into synchronous and asynchronous multiplexing.
A single bandwidth path divides into shorter paths to transmit more than one signal. A multiplexer merges signals of all nodes and loads the data on the path. The demultiplexer at the receiving end unloads and separates the signals and passes them to the respective nodes.
Other Applications of Multiplexing
Different forms of networking and communication today use the multiplexing and demultiplexing services. Communication systems use multiplexers such as transmission systems, relays, tributary systems, etc. They are also used in telephone networks for transmitting more than one audio signal that separates depending on the receiver address. Frequency division is also used by TV networks for transmission as well as by radio stations for broadcast of services like AM and FM. The choice of the type of different multiplexing techniques is made according to the need and the preference of factors such as speed, time, etc.
