Paper DSC 103: FUNDAMENTALS OF INFORMATION TECHNOLOGY
UNIT-V
DATA
COMMUNICATION
Data: Data refers to
raw facts which are processed to generate information. Data can be represented
either in the form text, numbers, images, etc.
Communication: Communication is defined as exchanging the information between two different objects. This information includes messages, pictures, etc.
Data
Communication:
Data communication refers to exchange the digital information between the
devices through a communication channel.
Data
Communications Characteristics:
1--Delivery
2--Accuracy
3--Timeliness
4--Jitter
-Delivery.
The system must deliver data to the correct destination.
-Accuracy.
The system must deliver the data accurately.
-Timeliness.
The system must deliver data in a timely manner. Data delivered late are
useless. In the case of video and audio, timely delivery means delivering data
as they are produced, in the same order that they are produced, and without
significant delay. This kind of delivery is called real-time transmission.
-Jitter. Jitter refers to the variation in the packet arrival time. It is the uneven delay in the delivery of audio or video packets.
Communication Process
Components
A
data communications system has five components
Message:
The message is the information (data) to be communicated. Popular forms of
information include text, numbers, pictures, audio, and video.
Sender:
The sender is the device that sends the data message. It can be a computer,
workstation, telephone handset, video camera, and so on.
Receiver:
The receiver is the device that receives the message. It can be a computer,
workstation, telephone handset, television, and so on.
Transmission
medium: The transmission medium is the physical path by
which a message travels from sender to receiver.
Basic Networking Devices
NIC (National interface card): NIC
is a device that helps the computer to communicate with another device.
The network interface card contains the
hardware addresses, the data-link layer protocol use this address to
identify the system on the network so
that it transfers the data to the correct destination.
There are two types of NIC: wireless NIC
and wired NIC.
➢
Wireless NIC: All the modern laptops use the wireless
NIC. In Wireless NIC, a connection is made using the antenna that employs the
radio wave technology.
➢
Wired NIC: Cables use the wired NIC to transfer the
data over the medium.
Hub: Hub is a
central device that splits the network connection into multiple devices. When
computer requests for information from a computer, it sends the request to the
Hub. Hub distributes this request to all the interconnected computers.
Switches: Switch
is a networking device that groups all the devices over the network to transfer
the data to another device. A switch is better than Hub as it does not
broadcast the message over the network. Switch sends the message directly from
source to the destination.
Cables: Cable
is a transmission media that transmits the communication signals. There are
three types of cables.
-Twisted pair cable: It
is a high-speed cable that transmits the data over 1 GBPS or more.
-Coaxial cable: Coaxial
cable resembles like a TV installation cable. Coaxial cable is more expensive
than twisted pair cable, but it provides the high data transmission speed.
-Fiber optic cable: Fiber optic cable is a high-speed cable that transmits the data using light beams. It provides high data transmission speed as compared to other cables. It is more expensive as compared to other cables. Used for Tele communication lines, ..., etc.
Router: Router
is a device that connects the LAN to the internet. The router is mainly used to
connect the
distinct networks or connect the
internet to multiple computers.
Modem: Modem connects the computer to the internet over the existing telephone line.
A modem is not integrated with the computer motherboard. A modem is a separate part on the PC slot found on the motherboard.
Repeater: A
repeater operates at the physical layer. Its job is to regenerate the signal
over the same network before the signal becomes too weak or corrupted so as to
extend the length to which the signal can be transmitted over the same network.
Gateway: A
gateway is used to connect two networks upon different networking models.
Gateways are also called protocol converters and can operate at any network layer.
Gateways are generally more complex than switch or router
Data Transmission Speed:
Bandwidth: Range of
frequencies available for data transmission. It refers to data transmission
rate. Higher the bandwidth, the more data it can transmit
Baud: Unit of
measurement of data transfer rate. Measured in bits per second (bps)
Narrowband: Sub-voice
grade channels in range from 45 to 300 baud. Mainly used for telegraph lines
and low-speed terminals
Voiceband: Voice grade
channels with speed up to 9600 baud. Mainly used for ordinary telephone voice communication
and slow I/O devices
Broadband: High speed channels with speed up to 1 million baud or more. Mainly used for high-speed computer-to-computer communication or for simultaneous transmission of data
Communication
Types(modes):
Q2) Explain
about Communication Types( Transmission modes)?
Ans: Transmission mode means transferring of data between two devices. It is also known as communication mode.
There
are three types of transmission mode
·
Simplex Mode
·
Half-Duplex Mode
· Full-Duplex Mode
Simplex
§ In
simplex mode, the communication is unidirectional, as on a one-way street.
§ Only
one of the two devices on a link can transmit; the other can only receive .
§ The
simplex mode can use the entire capacity of the channel to send data in one
direction.
Examples:
Keyboards and
traditional monitors are examples of simplex devices.
Advantage of Simplex mode:
- In simplex mode, the
station can utilize the entire bandwidth of the communication channel, so that
more data can be transmitted at a time.
- The main advantage of the simplex
mode is that the full capacity of the communication channel can be utilized during
transmission.
Disadvantage of Simplex mode:
- Communication is unidirectional, so it has no
inter-communication between devices
Half-Duplex
§ 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
.
§ In
a half-duplex transmission, the entire capacity of a channel is taken over by
whichever of the two devices is transmitting at the time.
§ The
half-duplex mode is used in cases where there is no need for communication in
both directions at the same time .
§ The
half-duplex mode is like a one-lane road with traffic allowed in both
directions. When cars are traveling in one direction, cars going the other way
must wait.
Examples:
Walkie-talkies
and CB (citizens band) radios
Advantage
of Half-duplex mode: In half-duplex mode, both the devices
can send and receive the data and also can utilize the entire bandwidth of the
communication channel during the transmission of data.
Disadvantage of Half-Duplex mode: In half-duplex mode, when one device is sending the data, then another has to wait, this causes the delay in sending the data at the right time.
Full-Duplex
§ In
full-duplex mode (duplex mode), both stations can transmit and receive
simultaneously .
§ The
full-duplex mode is like a two-way street with traffic flowing in both
directions at the same time.
§ In
full-duplex mode, signals going in one direction share the capacity of the
link: with signals going in the other direction.
§ This
sharing can occur in two ways:
Either the link must contain two physically separate transmission paths, one
for sending and the other for receiving; or the capacity of the channel is
divided between signals traveling in both directions.
§ One
common example of full-duplex communication is the
telephone network.
§ The
full-duplex mode is used when communication in both directions is required all
the time. The capacity of the channel, however, must be divided between the two
directions.
Advantage of
Full-duplex mode:
· Both
the stations can send and receive the data at the same time.
· The
Full-duplex mode is the fastest mode of communication between devices.
Disadvantage of
Full-duplex mode:
· If
there is no dedicated path exists between the devices, then the capacity of the
communication channel is divided into two parts.
--O--
Data
Transmission Medias
Q3)Explain Data
transmission medias?(VVIMP)
Ans: A transmission medium can be
broadly defined as anything that can carry information from a source to a
destination.
For example, a written
message, the transmission medium might be a mail carrier, a truck, or an
airplane.
In
telecommunications, transmission media can be divided into two broad
categories:
•
Guided
•
Unguided
GUIDED MEDIA:
It is defined as the physical medium through which the signals are transmitted. It is also known as Bounded media. In this type of media, a physical path is established between source and destination.
Types of Guided
media:
1. Twisted pair: Twisted pair is a physical media made up of a pair of cables twisted with each other. A twisted pair cable is cheap as compared to other transmission media. Installation of the twisted pair cable is easy, and it is a lightweight cable. The frequency range for twisted pair cable is from 0 to 3.5 KHz. A twisted pair consists of two insulated copper wires arranged in a regular spiral pattern.
Advantages:
· It
is cheap in cost.
· Used for telephone lines that have low-speed data.
Disadvantage:
-Used for
shorter distances.
-It is more expensive as compared to UTP and coaxial cable.
2.Coaxial Cable: Coaxial cable is
very commonly used transmission media, for example, TV wire is usually a
coaxial cable. The name of the cable is coaxial as it contains two conductors
parallel to each other. It has a higher frequency as compared to Twisted pair
cable.
The inner
conductor of the coaxial cable is made up of copper, and the outer conductor is
made up of copper mesh. The middle core is made up of non-conductive cover that
separates the inner conductor from the outer conductor. The middle core is
responsible for the data transferring whereas the copper mesh prevents from the
EMI(Electromagnetic interference).
Coaxial cable is
of two types.
1. Baseband
transmission: It
is defined as the process of transmitting a single signal at high speed.
2. Broadband transmission: It is defined as the process of transmitting multiple signals simultaneously.
Advantages of
Coaxial cable:
· The
data can be transmitted at high speed.
· It
has better shielding as compared to twisted pair cable.
· It provides higher bandwidth.
Disadvantages Of
Coaxial cable:
· It
is more expensive as compared to twisted pair cable.
· If any fault occurs in the cable causes the failure in the entire network.
3. Fiber
Optic: Fiber
optic cable is a cable that uses electrical signals for communication. Fiber
optic is a cable that holds the optical fibers coated in plastic that are used
to send the data by pulses of light. The plastic coating protects the optical
fibers from heat, cold, electromagnetic interference from other types of
wiring. Fiber optics provide faster data transmission than copper wires.
Basic elements
of Fiber optic cable:
Core: The optical
fiber consists of a narrow strand of glass or plastic known as a core. A core
is a light transmission area of the fiber. The more the area of the core, the
more light will be transmitted into the fiber.
Cladding: The concentric
layer of glass is known as cladding. The main functionality of the cladding is
to provide the lower refractive index at the core interface as to cause the
reflection within the core so that the light waves are transmitted through the
fiber.
Jacket: The protective
coating consisting of plastic is known as a jacket. The main purpose of a
jacket is to preserve the fiber strength, absorb shock and extra fiber
protection.
Following are
the advantages of fiber optic cable over copper:
Greater
Bandwidth: The
fiber optic cable provides more bandwidth as compared copper. Therefore, the
fiber optic carries more data as compared to copper cable.
Faster speed: Fiber optic
cable carries the data in the form of light. This allows the fiber optic cable
to carry the signals at a higher speed.
Longer
distances: The
fiber optic cable carries the data at a longer distance as compared to copper
cable.
Better
reliability: The
fiber optic cable is more reliable than the copper cable as it is immune to any
temperature changes while it can cause obstruct in the connectivity of copper
cable.
Thinner and Sturdier: Fiber optic cable is thinner and lighter in weight so it can withstand more pull pressure than copper cable.
UNGUIDED
TRANSMISSION
· An
unguided transmission transmits the electromagnetic waves without using any
physical medium. Therefore it is also known as wireless transmission.
· In
unguided media, air is the media through which the electromagnetic energy can
flow easily.
Unguided
transmission is broadly classified as follows:
A) Radio Waves
· Radio
waves are the electromagnetic waves that are transmitted in all the directions
of free space. Radio waves are uni directional, i.e., the signals are
propagated in all the directions.
· The
range in frequencies of radio waves is from 3Khz to 1 khz.
· In
the case of radio waves, the sending and receiving antenna are not aligned,
i.e., the wave sent by the sending antenna can be received by any receiving
antenna.
· An example of
the radio wave is FM radio.
Applications Of
Radio waves:
· A
Radio wave is useful for multicasting when there is one sender and many
receivers.
· An FM radio, television, cordless phones are examples of a radio wave.
Advantages Of
Radio transmission:
· -Radio
transmission is mainly used for wide area networks and mobile cellular phones.
· -Radio
waves cover a large area, and they can penetrate the walls.
· -Radio transmission provides a higher transmission rate.
B) Microwaves
Microwaves are
of two types:
1. Terrestrial
microwave
2. Satellite
microwave communication.
1. Terrestrial
Microwave Transmission
Terrestrial
Microwave transmission is a technology that transmits the focused beam of a
radio signal from one ground-based microwave transmission antenna to another.
Microwaves are
the electromagnetic waves having the frequency in the range from 1GHz to 1000
GHz.
Microwaves are
unidirectional as the sending and receiving antenna is to be aligned, i.e., the
waves sent by the sending antenna are narrowly focused.
In this case,
antennas are mounted on the towers to send a beam to another antenna which is
km away.
It works on the
line of sight transmission, i.e., the antennas mounted on the towers are the
direct sight of each other.
Characteristics
of Microwave:
Frequency range: The frequency
range of terrestrial microwave is from 4-6 GHz to 21-23 GHz.
Bandwidth: It supports the
bandwidth from 1 to 10 Mbps.
Short distance: It is
inexpensive for short distance.
Long distance: It is expensive
as it requires a higher tower for a longer distance.
Attenuation: Attenuation
means loss of signal. It is affected by environmental conditions and antenna
size.
Advantages Of
Microwave:
· Microwave
transmission is cheaper than using cables.
· It
is free from land acquisition as it does not require any land for the
installation of cables.
· Microwave
transmission provides an easy communication in terrains as the installation of
cable in terrain is quite a difficult task.
·
Communication
over oceans can be achieved by using microwave transmission.
Disadvantages of
Microwave transmission:
· Eavesdropping: An eavesdropping creates
insecure communication. Any malicious user can catch the signal in the air by
using its own antenna.
· Out of phase signal: A signal can be
moved out of phase by using microwave transmission.
· Susceptible to weather condition: A microwave
transmission is susceptible to weather condition. This means that any
environmental change such as rain, wind can distort the signal.
· Bandwidth limited: Allocation of bandwidth is
limited in the case of microwave transmission.
2. Satellite
Microwave Communication
· Satellite
is a physical object that revolves around the earth at a known height.
Satellite communication is more reliable nowadays as it offers more flexibility
than cable and fibre optic systems. We can communicate with any point on the
globe by using satellite communication.
· The
satellite accepts the signal that is transmitted from the earth station, and it
amplifies the signal. The amplified signal is retransmitted to another earth
station.
Advantages Of
Satellite Microwave Communication:
· The
coverage area of a satellite microwave is more than the terrestrial microwave.
· The
transmission cost of the satellite is independent of the distance from the
centre of the coverage area.
· Satellite
communication is used in mobile and wireless communication applications.
· It
is easy to install.
· It
is used in a wide variety of applications such as weather forecasting, radio/TV
signal broadcasting, mobile communication, etc.
Disadvantages Of
Satellite Microwave Communication:
· Satellite
designing and development requires more time and higher cost.
· The
Satellite needs to be monitored and controlled on regular periods so that it
remains in orbit.
· The
life of the satellite is about 12-15 years. Due to this reason, another launch
of the satellite has to be planned before it becomes non-functional
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