Computer Network -II

Modulation Techniques:

​Radio waves and microwaves etc are used for carrying data or messages.

How these waves carry messages??

It is the result of a particular technique called modulation.

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Modulation is a process of changing the characteristics of the wave to be transmitted, i.e., the carrier wave, by superimposing the message signal of a high-frequency signal.

Modulation Techniques

A carrier wave by itself doesn't carry much information, to include a message, another wave, a

message signal that carries the data to be transmitted, needs to be imposed on top of the carrier

signal. This process is termed as modulation.

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Frequency modulation is a technique or a process of encoding information on a particular signal (analogue or digital) by varying the carrier wave frequency in accordance with the frequency of the modulating signal.

Frequency Modulation (FM)

Amplitude Modulation (AM)​

Modulation​

Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal.

​The super imposing of message signal and carrier wave results into a new wave called the modulated wave.

Noise Immunity- High Uses- It is generally used in transmitting radio waves lying in a very high frequency range. Application: FM radio broadcasting. Video broadcasting, two-way radio systems, etc.

Frequency Modulation (FM)

Noise Immunity- Low Uses -It is generally used for transmitting radio waves over short and long distances.

Application: Radio communication, electronics communication, etc.

Amplitude Modulation (AM)

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Multiple Choice

Converting a digital signal in to an analog signal is called

• modulation

• demodulation

• conversion

• transformation

Multiple Choice

Process of superimposing a low frequency signal over a high frequency signal is called

• modulation

• demodulation

• frequency modulatiton

• amplitude modulation

Multiple Choice

Process of superimposing the amplitude message signal over amplitude of carrier signal is called

• modulation

• demodulation

• frequency modulatiton

• amplitude modulation

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What is modulation?

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What is c?

Open Ended

What is modulated wave?

Collision

Many devices (nodes) are connected with one wireless network. If multiple nodes on the same network transmit data at the same time, it leads to a condition called collision and data gets lost. In a computer network, collision is a specific condition that occurs when two or more nodes on a network transmit data at the same time.​​

It is something like when two or more people are quarrelling with each other and speaking at the same time, but no one is listening to no one.

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Full Duplex

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​Half Duplex

Collision

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​IMPORTANT

Open Ended

Explain collision in a network ?

Open Ended

What measures do wireless networks employ to avoid collision?