types of multiplexing

8/4/2019 Types of Multiplexing

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Multiplexing

Groupmembers

* Harpreetkaur


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What is Multiplexing

It is the process of sending signalsfrom two or more different sourcessimultaneously over a singlecommunication channel.

Multiplexing is done by using adevice called multiplexer(MUX) thatcombines n input lines to gernate oneoutput line i.e (many to one).Thereforemultiplexer (MUX) has serval inputs oneoutput.

At the receiving end , a device

demultiplexer (DEMUX) is used that


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Types of Multiplexing

Frequency Division Multiplexing (FDM) Wave Division Multiplexing (WDM) Time Division Multiplexing (TDM)


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Frequency Division Multiplexing

It is analog technique. In FDM, signals of different frequencies arecombined into a single composite signal and

is transmitted on single link.

FDM requires that the bandwidth of a linkshould be greater than the combinedbandwidths of various signals to betransmitted. Thus each signal having different frequency

from a particular logical channel on the linkand follow this channel only. These channels are then separeted by thestrips of unused bandwidth called gurad

band.These gurad bands band prevent the


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Frequency Division Multiplexing

In FDM signals to be transmitted must beanalog signals. Thus digital signals need to beconverted to analog form, if they are to useFDM.


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Applications of FDM

FDM is used for FM & AM radio broadcasting.Each AM & FM radio stations uses a differentcarries frequency . FDM is used in television broadcasting.

First generation cellular telephone also usesFDM.


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Wave Division Multiplexing

WDM is the analog multiplexingtechnique.WDM is conceptually similar to FDM,in sense that it combines different signals ofdifferent signals of different frequencies into

single composite signal and transmit it on asingle link. In WDM the different signals are optical orlight signals that are transmitted throughoptical fiber.Wavelength goes up down and

vice-verse. In WDM various waves from different sourcesare combined to form composite light signalthat is transmitted across the channels to the

different receiver.


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Wave Division Multiplexing

At the receiver side, this composite lightsignal is broken into different light waves bydemultiplexer. This combines and splitting of light waves is

not by using a prism. One prism is used at the sender side toperform multiplexing and another prism is usedat receiver side that perform demultiplexing. The basic principal behind the usage of prism

is that,the prism bends a beam of light basedon the angle of incidence and the frequency oflight wave.


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Applications of WDM

WDM is used in SONET(Synchronous OpticalNetwork).It makes use of multiple optical fiberlines which are multiplexed & demultiplexed.


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Time Division Multiplexing

TDM is a digital multiplexing technique. In TDM, the channels is not divided on thebasis of frequency but on the basic of time. Total time available in the channel is divided

between serveral users. Each time is allotted a particular a timeinterval called time slot during which the datais transmitted by that user. Each sending device takes control of entire

bandwidth .


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Time Division Multiplexing

There are two types of TDM* Synchronous TDM* Asynchronous TDM


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Synchronous TDM

Multiplexer allots the same time slot to eachdevice at all time either device having data ornot. If there are n input lines then there are n

slots in one frame. Number of slots = No ofinput lines. Synchronous TDM does not give guaranteethat full capacity of link is used . The no of time slot in a frame is always based

on no of input devices . The time slots are fixed and predefined.


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Asynchronous TDM

It is also known as STATISTICAL TDM.Multiplexer does not allots same time slot toeach device at all time . Time slots are flexibleand not fixed.

If there are n input lines then there are mslots perform. m is less than n. Asynchronous TDM give guarantee that fullcapacity of link is used . The no of time slot in a frame is always based

on statistical analysis of no of input devices. The time slots are not fixed and predefined.


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Reference: Charanjeet singh(kalyani Publisher)

types of multiplexing

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