What is Multiplexing : Types & Their Applications

The term “Multiplexing” or “Muxing” is one kind of technique for combining multiple signals like analog as well as digital into one signal over a channel. This technique is applicable in telecommunications as well as computer networks. For instance, in telecommunications, one cable is used for carrying different telephone calls. In the year 1870, the multiplexing technique is invented first in telegraphy, and at present, it is extensively used in communications. The scientist “George Owen Squier” was recognized the growth of multiplexing in telephony in the year 1910. The signal which is multiplexed will be transmitted over a cable or channel and separates the channel into numerous logic channels. This article discusses what is multiplexing, Different types of multiplexing techniques, and applications. Please refer to the link to know about Multiplexer and Demultiplexer – Electronics Circuits

What is a Multiplexing?

Muxing (or) multiplexing can be defined as; it is a way of transmitting various signals over a media or single line. A common kind of multiplexing merges a number of low-speed signals to send over an only high-speed link, or it is used to transmit a medium as well as its link with a number of devices. It provides both privacy & Efficiency.


The entire process can be done using a device namely MUX or multiplexer, and the main function of this device is to unite n-input lines for generating a single output line. Thus MUX has many inputs & single output. A device is called DEMUX or demultiplexer is used at the receiving end which divides the signal into its component signals. So It has a single input and a number of outputs.

Multiplexing
Multiplexing

Multiplexing in Computer Networks

Multiplexing in computer networks is one kind of method used to merge and transmit several data signals above a single medium. In this technique, hardware like multiplexer or MUX plays a key role in achieving multiplexing. Multiplexer merges ‘n’ input lines for producing an only output line. This technique mainly follows the many-to-one concept that means n-input lines & 1-output line.

For demultiplexing, a device like DEMUX is used at the receiving end to separate a signal into many. Thus, this technique follows the single-to-many concept that means single input lines & n-output lines. This technique separates a logic medium from high-capacity to a low-capacity, and then it is transmitted through many streams from a medium with high-capacity to low-capacity.

Communication is possible in the air on radio frequency through a cable & light which are capable of multiplexing. Once many senders try to transmit the signals using a single channel, then a tool like Multiplex is used to divide the physical channel & allocates each one.


Why Multiplexing is Required?

The main function of the transmission medium is to transmit the signals from transmitter to receiver. Here, the medium simply includes a single signal at a time. So, if several signals need to transmit a single medium, then they should be separated in such a way that each signal is given some part of the obtainable bandwidth.

For instance: If there are 5 signals & the medium bandwidth is 50 units, then the 5 units can be shared through every signal. Once multiple signals transmit the common medium, there is a chance of a crash. So, the concept of this technique is mainly used to evade such crashes.

History of Multiplexing

In telecommunications, the method like Multiplexing is extensively used where numerous telephone calls are carried throughout an only wire. In the year 1870, this concept was invented in telegraphy and it is used in communication.

Similarly, in the year 1910, the telephone carrier multiplexing technique was implemented by George Owen Squier. He is very famous in both the countries like in the United States & in Europe as a scientist, inventor, and soldier.

Types of Multiplexing Techniques

These techniques are mainly used in communication, and these are classified into three types. The 3 types of multiplexing techniques include the following.

  • Frequency Division Multiplexing (FDM)
  • Wavelength Division Multiplexing (WDM)
  • Time Division Multiplexing (TDM)

Frequency Division Multiplexing (FDM)

The FDM is used in telephone companies in the 20th century in long-distance connections for multiplexing a number of voice signals using a system like a coaxial cable. For small distances, low-cost cables were utilized for different systems such as bell systems, K-and N-carrier, however, they don’t let huge bandwidths. This is analog multiplexing used to unite analog signals. This type of technique is useful when the link’s bandwidth is better than the United bandwidth of the transmitted signals.

Frequency Division Multiplexing
Frequency Division Multiplexing

In FDM, signals are produced by transmitting various device modulated carrier frequencies, and then these are united into a solo signal which can be moved by the connection. To hold the adapted signal, the carrier frequencies are divided by sufficient bandwidth, & these ranges of bandwidths are the channels through the different traveling signals. These can be divided by bandwidth which is not used. The best examples of the FDM comprise signal transmission in TV and radio.

Wavelength Division Multiplexing (WDM)

In fiber communications, the WDM is one type of technology. This is the most useful concept in high-capacity communication systems. At the end of the transmitter section, the multiplexer is used to combine the signals as well as at the end of the receiver section, the de-multiplexer for dividing the signals separately. The main function of WDM at the multiplexer is for uniting various light sources into only light sources, and this light can be changed into numerous light sources at the de-multiplexer.

WDM
WDM

The main intention of WDM is to utilize the high data rate capacity of the FOC (fiber optic cable). The high data rate of this FOC cable is superior to the data rate of the metallic transmission cable. Theoretically, the WDM is similar to the FDM, apart from the data transmission through the FOC in which the multiplexing & de-multiplexing occupies optical signals. Please refer to the link to know more about Wavelength Division Multiplexing (WDM) Working and Applications

Time Division Multiplexing (TDM)

The TDM is one kind of method for transmitting a signal over a channel of particular communication by separating the time edge into slots. Like single slot is used for each message signal.

Time Division Multiplexing
 Time Division Multiplexing

TDM is mainly useful for analog and digital signals, in which several channels with low speed are multiplexed into high-speed channels used for transmission. Depending on the time, every low-speed channel will be assigned to an exact position, wherever it works in the mode of synchronization. Both the ends of MUX and DEMUX are synchronized timely & at the same time switch toward the next channel.

Types of TDM

The different types of TDM include the following.

  • Synchronous TDM
  • Asynchronous TDM
  • Interleaving TDM
  • Statistical TDM
Types of TDM
 Types of TDM

Synchronous TDM

The synchronous TDM is very useful in both analogs as well as digital signals. In this type of TDM, the connection of input is allied to a frame. For example, if there are n-connections in the frame, then a frame will be separated into n-time slots, and for every unit, each slot is assigned to every input line.

In the sampling of synchronous TDM, the speed is similar for every signal, as well as this sampling needs a clock (CLK) signal at both the ends of sender & receiver. In this type of TDM, the multiplexer assigns a similar slot for each device at every time.

Asynchronous TDM

In asynchronous TDM, for different signals, the rate of sampling is also different, and it doesn’t need a general clock (CLK). If the device has nothing for transmitting, then the time slot is assigned to a new device. The design of a commutator otherwise de-commutator is not easy & the bandwidth is low for this type, and it is applicable for not synchronous transmit form network.

Interleaving TDM

The TDM can be imagined like two speedy rotary switches on the multiplexing & demultiplexing surface. These switches can be rotated & synchronized in reverse directions. Once the switch releases at the surface of the multiplexer ahead of a connection, then it has a chance of sending a unit into the lane. Similarly, once the switch releases at the surface of the de-multiplexer ahead of a connection a chance to receiving a unit from the lane. This procedure is named interleaving.

Statistical TDM

The statistical TDM is applicable to transmit different types of data simultaneously across a single cable. This is frequently used to handle data being transmitted through a network like LAN (or) WAN. The transmission of data can be done from the input devices which are connected to networks like computers, fax machines, printers, etc.

The statistical TDM can be used in the settings of telephone switchboards to control the calls. This type of technique is comparable to dynamic bandwidth distribution, and a communication channel is separated into a random data stream number.

Code Division Multiplexing

The term CDM stands for code division multiplexing. It is one kind of technology that works with spread spectrum communication. In this type of communication, a narrowband signal can be transmitted through division across several channels or over a larger frequency band.

It does not compress the bandwidths of frequencies otherwise digital signals. It is less liable to intrusion, so providing enhanced data communication capacity as well as a more safe private line.
Once code division multiplexing is used to permit several signals from different users to transmit a communication channel commonly, then this technology is known as CDMA or Code Division Multiple Access.

Orthogonal Frequency Division Multiplexing

The term OFDM stands for “Orthogonal Frequency Division Multiplexing” and it is a type of signal otherwise modulation that offers some important benefits for data links. So, OFDM is mainly used for several most recent wide bandwidth & wireless systems with high data rates like cellular telecommunications, Wi-Fi, etc.

OFDM uses a large number of carriers where each carrier holds low bit rate data that means it is very flexible to preferred fading, intrusion, multipath effects & provides a high amount of spectral efficiency.
OFDM-based early systems found the processing which is necessary for the signal format fairly high, however with progress in technology, this kind of technique presents few issues in terms of the required process.

Space Division Multiplexing

Space division multiplexing is one kind of technique where radio, metallic otherwise optical transmission media are separated physically through insulation and space or waveguides keeps channel separations.

In each physically different channel, numerous channels can be attained through time, frequency, otherwise WDM. Some POV (Passive Optical Network) implementations use SDM or space division multiplexing, through the downstream transmissions which occur on one of a duplex FOC (fiber optic cable) whereas upstream transmission occurs on the remaining fiber.

Which Multiplexing Technique Transmits Digital Signals?

Time Division Multiplexing or TDM is used for transmitting digital signals. The techniques like WDM & FDM are mainly used for transferring analog signals. Wave Division (WDM) is partially related to Frequency Division (FDM).

Advantages

The process which is used to transmit multiple signals over a single physical medium is known as multiplexing. The main advantages of multiplexing include the following.

  • Above one signal can be transmitted over a single medium.
  • The utilization of a medium bandwidth can be done very effectively
  • Multiplexing enhances the network’s economic stability because it reduces both the time as well as cost required for the operation of the physical medium when a single medium serves many signals or subscribers or applications.
  • In telecommunications, multiplexing plays a key role to reduce the cost of networks through reducing the number of communications links required among two points.

Applications

The applications of multiplexing include the following.

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

Thus, this is all about an overview of multiplexing in networking and its types like analog multiplexing and digital multiplexing. Analog type uses analog signals which are multiplexed based on their frequency or wavelength. So these are classified into two types like frequency division or FDM & wavelength division or WDM. Digital type uses discrete data bits. Thus, the available data is in the form of packets/ frames because these are discrete. This kind of technique is classified into different types like time division, synchronous and asynchronous.

From the above information finally, we can conclude that by using these types of multiplexing techniques we can transfer and receive the data efficiently. Here is a question for you, what is demultiplexing?

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