# Multiplexing in Computer Networks

In this tutorial, we will know about Multiplexing in computer networks.

Multiplexing is a method of both combining and transmitting numerous data streams over a single channel. Multiplexing is accomplished using a device known as a Multiplexer (MUX). It combines n input lines into a single output line. Many-to-one multiplexing means there are n input lines and one output line.

At the receiving end, a device called a De-multiplexer (DEMUX) is to demultiplex the signal. DEMUX splits a signal into its constituent signals (one input and n outputs). As a result, we can say that demultiplexing is a one-to-many process.

## Types of Multiplexing in Computer Networks :

### Frequency Division Multiplexing (FDM) :

FDM is basically useful when the carrier is frequency. It is a technology that uses analogue signals. FDM generally divides the spectrum or carrier bandwidth into logical channels, each with a single user. Each user has unique access to the channel frequency and can utilize it independently. All of the channels are split in such a way that they don’t overlap. Guard bands separate the channels. The guard band is a frequency that neither channel uses. When low-speed channels are necessary, we use the FDM approach . It has a problem with crosstalk. It is necessary to use a large number of modulators.

### Time Division Multiplexing (TDM) :

TDM is typically useful with digital communications, but we can also use it with analogue signals. The shared channel in TDM is divided among its users by time slot. Each user have to transmitting data during the time period allotted to them. Digital signals consists of frames, which are the same as time slots. A frame of optimal size that we can deliver in a given time slot is a frame. TDM operates in a coordinated manner. Both ends, the Multiplexer and the De-multiplexer, are synchronized and switch to the next channel at the same time. TDM are of two types: synchronous and asynchronous.

### Wavelength Division Multiplexing :

The wavelengths of light are varied (colors). In fiber optic mode, different wavelengths basically multiplex numerous optical carrier signals into one optical cable. This is an analogue multiplexing technology that works in the same way as FDM but with light as the signal. Time division multiplexing can also be useful for each wavelength to accommodate more data transmissions.

### Code Division Multiplexing in Computer Networks:

Code Division Multiplexing sends several data signals over a single frequency. FDM divides the frequency into smaller channels, but CDM allows users to use the entire bandwidth and transmit signals using a unique code all of the time. To distribute signals, CDM employs orthogonal coding. A unique code, basically known as a chip, each station has it. Signals flow independently with these codes throughout the entire bandwidth. The receiver must receive a predetermined chip code signal.