Multiplexing

Multiplexer phone

In telecommunications, multiplexing is the technique of combining two or more signals, and transmitting them over a single transmission medium. The main advantage is that it allows several communications simultaneously, using a device called a multiplexer. The reverse process is known as demultiplexing. A very similar concept is that of media access control.

There are many multiplexing strategies depending on the communication protocol used, you can combine them to achieve the most efficient use; the most used are:

• multiplexing by time division or synchronous TDM (Time division multiplexing );
• statistical multiplexation or asynchronous TDM or statistical TDM (technical more advanced than the previous one);
• Multiplexation by frequency division or FDM (Frequency-division multiplexing) and its equivalent for optical means, by division of wavelength or WDM (of Wavelength);
• multiplexing by division in code or CDM (Code division multiplexing);

When there is a multiplexing scheme or protocol intended for multiple users to share a common medium, such as mobile telephony or WiFi, it is often called medium access control or multiple access method. As multiple access methods, the following stand out:

• multiple access by frequency division or FDMA;
• multiple access by time division or ADHD;
• multiple access by code division or CDM.

Multiplexing in computing

In computing and electronics, multiplexing refers to the same concept when it comes to data buses that have to be shared between various devices (disks, memory, etc.). Another type of multiplexing in computing is that of the CPU, in which a process is assigned a quantum of time during which it can execute its instructions, before giving up space to another process that is waiting in the ready process queue. to be dispatched by the process scheduler. Also in computing, it is called multiplexing to combine in the same container file, several tracks of two files, for example audio and video, for its correct reproduction, also in computing multiplexing a file, is a way that several identical copies of this file are kept, this to back up information in case a failure occurs in the main file.

Multiplexing in telecommunications

In telecommunications, multiplexing is used to divide signals into the medium through which they will travel within the radio spectrum. The term is equivalent to media access control.

In this way, to transmit the television channels over the air, we are going to have a frequency width x, which will have to be multiplexed so that the greatest possible number of TV channels can enter. The channels are then divided into a 6 MHz bandwidth (in much of Europe and America, while in other countries the bandwidth is 8 MHz). In this case, FDM frequency division multiplexing is used.

Multiplexing in Transport Layer Protocols in the OSI Model

Multiplexing a data packet means taking the data from the application layer, labeling it with a port number (TCP or UDP) that identifies the sending application, and sending the packet to the network layer.