What is Multiplexing: Need, Types and Advantages

The process through which multiple signals are transmitted over a physical medium is called as multiplexing. It is a method in computer networks that is used for merging and transmitting multiple data signals over single medium.

In this article on what is multiplexing, we will be discussing its requirement, types and advantages.

Table of Contents

• What is Multiplexing?
• Need
• Types
• Advantages

What is Multiplexing?

Multiplexing is a process where multiple signals are combined into one signal over a shared medium. This process divides a communication channel into multiple logical channels. Each one is allotted for a different message signal or data stream to be transferred. The hardware that is used for multiplexing is called as a multiplexer, which combines n number of input lines for generating a single output line. It follows many-to-one where there are n input lines and one output line. 

Requirement

The following reasons lead to the requirement of this process:

• It is used for sending a signal from the sender to the receiver, where only one signal can be transmitted from the medium at a time.
• When there are multiple signals for sharing one medium, the medium should be divided in a way that every signal is provided a portion of the available bandwidth.
• Whenever multiple signals share a common medium, it helps in avoiding possible collisions. 

Types of Multiplexers

There are two main types of multiplexers including analog and digital which are further subdivided.

1. Analog Multiplexing

It is used for telecommunication that involves signals which are analog in nature. These are analog signals that are multiplexed according to Frequency Division Multiplexing (FDM) or Wavelength Division Multiplexing (WDM). 

1.1 Frequency Division Multiplexing (FDM)

It is a technique of multiplexing that combines multiple signals over a shared medium. Signals of several frequencies are combined for concurrent transmission. Traditional television transmitter sends a number of channels via a single cable use FDM. 

1.2 Wavelength Division Multiplexing (WDM)

It is an analog technique where many streams of data with different wavelengths get transmitted in light spectrum. When the wavelength increases, frequency of the signal decreases. In WDM, optical signals from different sources get combined by a multiplexer.

2. Digital Multiplexing

In computer networking, digital multiplexing helps organizations in sending multiple signals over a single channel. The available data is in form of packets and frames that are discrete. 

2.1 Time Division Multiplexing (TDM)

It is a digital procedure where every sender has the possession of the entire bandwidth of channel for a fixed time duration. Beyond this duration, control moves to the next sender, and process continues on a round-robin basis. TDM is of the following three different types:

2.2.1 ATDM (Asynchronous Time Division Multiplexing)

It is also known as Statistical TDM that uses a technique in which time slots are not fixed. The time slots in ATDM are allotted to those devices that need to send the data. When a device is left with nothing to transmit, then that particular space is allotted to other devices. It allows full utilization of every slot more effectively than Synchronous TDM. 

2.2.2 STDM (Synchronous Time Division Multiplexing)

In STDM, there are a specific number of connections that divide the frame into multiple slots. Every time slot will run for an equal amount of time for which it has been programmed to run for. There are an equal number of devices to time slots where the time usually is about a millisecond. 

2.2.3 Interleaving TDM

Supposedly, TDM are two speedy rotary switches on multiplexing and demultiplexing surfaces which can be rotated and synchronized in the reverse direction. Once the switch releases at surface of multiplexer ahead of a connection, it has a chance of sending the unit into lane. Once the switch is released at the surface of the de-multiplexer ahead of a connection to receive a unit from the lane. 

2.2.4 Statistical Time Division Multiplexing (Statistical TDM)

It is a type fo communication link sharing that is identical to dynamic bandwidth allocation. The communication channel gets split into multiple ranges of variable bit-rate data streams, Here, the link sharing is adjusted for instantaneous traffic requirements of data streams that are transmitted over each channel. 

It is a replacement to create a fixed link sharing, such as in TDM and FDM. On precise execution, STDM offers an improvement in link utilization that is referred to as statistical multiplexing gain. 

Advantages of Multiplexing

The following are the major advantages of multiplexing:

• It boosts the economic scalability of networks since it lowers cost as well as the time required for deploying physical medium since single medium serves as multiple signals.
• Types of multiplexing are used in AM and FM broadcasting. 
• Frequency-division Multiplexing is a very simple and easy modulation that allows a large number of signals to be sent simultaneously.
• There is no need for synchronization between the sender and receiver.