presentation 1 li pika

8/13/2019 Presentation 1 Li Pika

1/14

Presented byLipika sahu

Roll No-Pc12IST018

BSCIST 2ndyear


2/14

MODULATIONModulation may be defined as the

process by which somecharacteristics of a signal calledcarrier is varied in accordance with

the instantaneous value of anothersignal called modulatingsignal/baseband signal.


3/14

Types of modulationAmplitude modulation (AM)

Phase shift keying (PSK)Quadrature amplitude

modulation(QAM)


4/14

Amplitude Modulation Amplitude modulation may be defined as system in which

maximum amplitude of the carrier wave is madeproportional to the instantaneous value of the modulating

or baseband signal. AM is a modulation technique used in electronic

communication ,most commonly for transmittinginformation via a radio carrier wave.

AM was the earliest modulation method used to transmitvoice by radio .

One disadvantage of AM is that it is inefficient in powerusage. at least two third of the power is concentrated in thecarrier signal.


5/14

Phase Shift Keying (PSK)

Data is represented by shift in the phase of a signal.

PSK is a digital modulation scheme that conveys databy changing or modulating the phase of a referencesignal(the carrier wave).


6/14

Quadrature amplitude

modulation(QAM) QAM is both an analog and a digital modulation

scheme.

It conveys two analog massage signals ,or two digitalbit streams by changing(modulating)the amplitudes oftwo carrier waves.

The application of QAM is- it is apply in colour TV.


7/14

MULTIPLEXING Multiplexing is the set of techniques that allows

the simultaneous transmission of multiple signals

across a single data link.A Multiplexer(MUX) is a device that combines

several signals into a single signal.

A Demultiplexer(DEMUX) is a device that

performs the inverse operation.


8/14


9/14

Categories of Multiplexing


10/14

Frequency Division Multiplexing

(FDM) Frequency division multiplexers can be described as

dividing the circuit horizontally so that many signals cantravel a single communication circuit simultaneously.

The circuit is divided into a series of separate channels,each transmitting on a different frequency.

Frequency division multiplexers are somewhat inflexiblebecause once you determine how many channels arerequired, it may be difficult to add more channels withoutpurchasing an entirely new multiplexer.


11/14

Wavelength Division Multiplexing Wavelength division multiplexing multiplexes multiple data

streams onto a single fiber optic line

Different wavelength lasers transmit the multiple signals

Each signal carried on the fiber can be transmitted at a different

rate from the other signals


12/14

Time Division Multiplexing

(TDM) Time division multiplexing shares a circuit among two or more

terminals by having them take turns, dividing the circuit

vertically.

Time on the circuit is allocated even when data are nottransmitted, so that some capacity is wasted when a terminal isidle.

Time division multiplexing is generally more efficient and lessexpensive to maintain than frequency division multiplexing.


13/14


14/14

presentation 1 li pika

Documents