Computer_Network_Chapter_1.pptx

B.L.D.E.Association’s
SHREE SANGANABASAVA MAHASWAMIJI POLYTECHNIC, VIJAYAPUR - 03
COMPUTER SCIENCE & ENGINEERING DEPARTMENT
Course: Computer Networks (20CS33P)
Lect./CSE

SHREE SANGANABASAVA MAHASWAMIJI POLYTECHNIC VIJAYAPUR – 03
MECHANICAL ENGINEERING DEPARTMENT
Course : Computer Networks Course Coordinator : Mr.
Week 1:
CO1: Select an appropriate communication technology for a given network and
ensure optimal performance by addressing issues arising from transmission
impairments.
Content:
Electromagnetic waves – Generation of electromagnetic waves and their
properties.
Electromagnetic spectrum – classification and applications.
Communication Systems – Basic elements of communication systems with block
diagram, List commonly used terms in electronic communication systems, Data
representation, Data flow, Modulation, Demodulation Analog and Digital Signals,
Periodic and Non-Periodic Signals, Sine Wave, Phase, Wavelength, Digital Signals,
Bitrate, Bit-length.

Electromagnetic waves:
Electromagnetic waves
consist of both electric and
magnetic field waves. These
waves oscillate (move) in
perpendicular planes with
respect to each other, and are
in phase.

Generation of Electromagnetic Waves: The creation of all electromagnetic
waves starts with a charged particle. Once in motion, this charged particle creates
an electric field and magnetic fields.
Electromagnetic Waves Properties:
• These waves travel at the speed of light.
• These waves do not require any medium for propagation.
• Electromagnetic waves travel in a transverse (crossways) form.
• Electromagnetic waves are not deflected by electric or magnetic field.
• These waves can be polarized.
• Electromagnetic Waves undergo interference and diffraction.

Electromagnetic
Spectrum: The
electromagnetic
spectrum is the range
of frequencies (the
spectrum) of
electromagnetic
radiation and their
respective
wavelengths.

Electromagnetic Spectrum Classification:
Sl. No Wave
1 Radio waves
2 Microwaves
3 Infrared radiation
4 Visible light
5 Ultraviolet radiation
6 X-rays
7 Gamma rays

Electromagnetic Spectrum Applications:
• Radio waves are used for communications,
• Radio waves are used in FM and AM radio.
• Radio waves are used to broadcast television signals.
• Microwaves can be used to heat and cook your food.
• Microwaves can be used in satellite communication.
• Infrared waves can also be used to create heat-sensitive and night-vision cameras.
• Infrared waves are used in remote controls.
• Visible light is used in Fibre optic communications.
• Ultraviolet is used in Energy efficient lamps, sun tanning.
• X-rays is used in Medical imaging and treatments.
• Gamma rays are used in Medical imaging and treatments.

Communication Systems: The fundamental purpose of a communication
system is the exchange of data between two devices. To make the
communication possible, the devices need to be connected through
some form of transmission medium, such as a wire cable or wireless.
Basic elements of communication systems with block diagram:
Communication is the process of transmission of information from one
point to another point.
The electronics equipments which are used for communication purpose
are called communication equipments. Different communication
equipments when assembled together form a communication system.

The essential components of a communication system are information
source, input transducer, transmitter, communication channel, receiver and
destination.
Information resource: The the function of an information source to
produce the required message which has to be transmitted. The message
may be message in the form of a word, group of words, code or symbol etc.
Input transducer: The function of an input transducer is the conversion of
one form of energy into another form. Actually the message produced by
an information source is not in electrical nature then an input transducer
converts it in the form of an electric signal.

Transmitter: This is used to process the electrical signal from different aspects
means the processing of signals like amplification and modulation of signal in order
to ease the transmission of signal through the channel.
The channel and the noise: Channel means the medium through which message
travels from transmitter to receiver or we can say it provides a physical connection
between the transmitter and receiver.
Receiver: The purpose of the receiver is to reproduce the message signal in
electrical form from the distorted received signal.
Destination/ Output transducer: Now destination is the last stage where the
electrical message signal is converted into its original form. Example in radio
broadcasting the destination is a loudspeaker who works as a transducer means it
converts the electrical signal in the form of original sound signal.

List commonly used terms in electronic communication systems:
1.Signal 8.Wavelength
2.Communication Channel 9.Amplification
3.Transducer 10.Bandwidth
4.Receiver 11.Modulation
5.Attenuation 12.Demodulation
6.Amplitude 13.Repeater
7.Frequency 14.Noise

Data representation: Information today comes in different forms
such as text, numbers, images, audio, and video.
1. Text: In data communications, text is represented as a bit pattern,
a sequence of bits (0’s or 1’s). Different sets of bit patterns have been
designed to represent text symbols. Today, the coding system is
called Unicode, which uses 32 bits to represent a symbol or character
used in any language in the world.
2. Numbers: Numbers are also represented by bit patterns. However,
the number is directly converted to a binary number to simplify
mathematical operations.

3. Images: Images are also represented by bit patterns. In its simplest
form, an image is composed of a matrix of pixels (picture elements), where
each pixel is a small dot. The size of the pixel depends on the resolution.
4. Audio: Audio refers to the recording or broadcasting of sound or music.
Audio is by nature different from text, numbers, or images. It is
continuous, not discrete. Even when we use a microphone to change voice
or music to an electric signal, we create a continuous signal.
5. Video: Video refers to the recording or broadcasting of a picture or
movie. Video can either be produced as a continuous entity (e.g. camera),
or it can be a combination of images, each a discrete entity, arranged to
convey the idea of motion.

Data flow: Communication between two devices can be simplex, half-duplex, or full-duplex.
Simplex Mode: In simplex mode, the communication is unidirectional. Only one of the two
devices on a link can transmit; the other can only receive.
Example: Keyboards and traditional monitors are examples of simplex devices. The keyboard
can only introduce input; the monitor can only accept output.

Half-Duplex Mode: In half-duplex mode, each station can both transmit and
receive, but not at the same time. When one device is sending, the other can only
receive, and vice versa.
Example: Walkie-talkies and CB(citizens band) radios are both half-duplex systems.

Full Duplex Mode: In full-duplex mode, both stations can transmit and receive
simultaneously.
Example: One common example of full-duplex communication is the telephone
network. When two people are communicating by a telephone line, both can talk
and listen at the same time.

Modulation: Modulation is defined as
the process of superimposing a low-
frequency signal on a high-frequency
carrier signal.
Demodulation: Demodulation is defined
as extracting the original information-
carrying signal from a modulated carrier
wave. A demodulator is an electronic
circuit that is mainly used to recover the
information content from the
modulated carrier wave.

Analog and Digital Signals:
An analog signal has infinitely
many levels of intensity over a
period of time.
A digital signal, on the other
hand, can have only a limited
number of defined values.
Although each value can be any
number, it is often as simple as
1 and 0.

Periodic and Non-Periodic Signals:
Both analog and digital signals can take one of two forms: periodic or non
periodic.
A periodic signal completes a pattern within a measurable time frame, called a
period, and repeats that pattern over subsequent identical periods. The
completion of one full pattern is called a cycle.
A non periodic signal changes without following a pattern or cycle that repeats
over time.

Sine Wave:
The sine wave is the most fundamental form of a periodic analog signal. When
we visualize it as a simple sine wave, its change over the time of a cycle is smooth
and consistent, a Continuous.
A sine wave can be represented by three parameters: the peak amplitude, the
frequency, and the phase. These three parameters fully describe a sine wave.

Phase:
The term phase describes the position of the waveform relative to time 0.
If we think of the wave as something that can shifted backward or forward along
the time axis, phase describes the amount of that shift. It indicates the status of
the first cycle.
A phase is measured in degrees or radians.

Looking at figure, we can say that
A sign wave with a phase of 0o starts at
time 0 with zero amplitude. The
amplitude is increasing.
A sign wave with a phase of 90o starts
at time 0 with zero amplitude. The
amplitude is decreasing.
A sign wave with a phase of 180o starts
at time 0 with zero amplitude. The
amplitude is decreasing.

Wavelength:
The wavelength is the distance that a simple signal can travel in one period.
The wavelength depends on both frequency and the medium.
Wavelength = propagation speed x period = Propagation speed/frequency

Digital Signals:
Information can also be represented by a digital signal. For example, 1 can be
encoded as a positive voltage and a 0 as zero voltage.
A digital signal can have more than two levels.
In general, if a signal has L levels, each level needs log2 L bits.
Bitrate:
The term-bit rate is used to describe digital signals.
The bit rate is the number of bits sent in 1s, expressed in bits per second (bps).
Bit-length:
The bit length is the distance one bit occupies on the transmission medium.
Bit length=propagation speed x bit duration

Course : Computer Networks
Thank You
For Any Questions / Suggestions please Contact
Mr. Sayyedzahidulla . R. InamdarLecturer
Computer Science & Engineering Department
B.L.D.E.A’s
Shree Sanganabasava Mahaswamiji Polytechnic,
Ashram road, Vijayapur – 03
Mobile : 9060997578
9060997578
Course Coordinator : Mr.

Computer_Network_Chapter_1.pptx

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