Multiplexing Techniques

 

What is a Multiplexing?

• Sharing the link among multiple users

In the year 1870, the multiplexing technique is invented first in telegraphy, and at present, it is extensively used in communications.

This blog explains different types of Multiplexing techniques

Introduction to Multiplexing

The term multiplexing is defined as a transmission method to transport different multiple analogs and digital signals into a single signal over a network or a channel.

The process of multiplexing divides a communication channel into several number of logical channels, allotting each one for a different message signal or a data stream to be transferred.

Do you know what is multiplexer and Demultiplexer?

In electronics, a multiplexer(MUX) also known as a data selector, is a device that selects between several analog or digital input signals and forwards it to a single output line.

Demultiplexer is quite opposite to multiplexer or MUX. It is a process of taking information from one input and transmitting over one of many outputs. 

What is Multiplexing Techniques?

Multiplexing is the process of combining multiple signals into one signal, over a shared    medium. If analog signals are multiplexed, it is Analog Multiplexing and if digital signals are multiplexed, that process is Digital Multiplexing.

Types of Multiplexing Techniques

Analog Multiplexing:

• Frequency Division Multiplexing
• Wavelength Division Multiplexing

1. Frequency Division Multiplexing (FDM)

In analog multiplexing, the most used technique is Frequency Division Multiplexing FDM. This technique uses various frequencies to combine streams of data, for sending them on a communication medium, as a single signal.

Concept and Process:

In FDM, the total bandwidth is divided to a set of frequency bands that do not overlap. The frequency bands are separated from one another by strips of unused frequencies called the guard bands, to prevent overlapping of signals.

 The combined signal is transmitted over the communication channel, At the receiving end, the individual signals are extracted from the combined signal by the process of demultiplexing (DEMUX).

Example: A traditional television transmitter, which sends a number of channels through a single cable, uses FDM.

   2. Wavelength Division Multiplexing (WDM)

Wavelength Division Multiplexing is an analog technique, in which many data streams of different wavelengths are transmitted in the light spectrum.

Concept and Process:

In WDM, the optical signals from different sources or (transponders) are combined by a multiplexer, which is essentially an optical combiner. They are combined so that their wavelengths are different.

The combined signal is transmitted via a single optical fiber strand. At the receiving end, a demultiplexer splits the incoming beam into its components and each of the beams is send to the corresponding receivers.

Example: Optical fibre Communications use the WDM technique, to merge different wavelengths into a single light for the communication.

Digital Multiplexing

• Time Division Multiplexing:

In TDM, the time frame is divided into slots. This technique is used to transmit a signal over a single communication channel, with allotting one slot for each message.

Of all the types of TDM, the main ones are Synchronous and Asynchronous TDM.

1. Synchronous TDM.

In Synchronous TDM, the input is connected to a frame. If there are ‘n’ number of connections, then the frame is divided into ‘n’ time slots. One slot is allocated for each input line. In this technique, the sampling rate is common to all signals and hence same clock input is given. The mux allocates the same slot to each device at all times

2. Asynchronous TDM.

In Asynchronous TDM, the sampling rate is different for each of the signals and the clock signal is also not in common. If the allotted device, for a time-slot, transmits nothing and sits idle, then that slot is allotted to another device, unlike synchronous.

Example:  It is widely used in telephone and cellular networks.

TDM and FDM both are multiplexing techniques. In TDM, syncronization pulse is important whereas in FDM, Guard Band is required

Applications of Multiplexing

The applications of multiplexing include the following.

• Analog Broadcasting
• Digital Broadcasting
• Telephony
• Video Processing
• Telegraphy

Putting it altogether

Thus, this blog covers all about what is multiplexing, different types of multiplexing techniques and also the examples of their usage. From the above information finally, we can conclude that by using these types of multiplexing techniques we can transfer and receive the data efficiently   and at present, it is extensively used in communications.