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Lecturer: Muhammad ShoaibOffice R-03, Amin Campus
[email protected] 8750971 ext 339
Data Communication
Data CommunicationData Communications are the exchange of data
between two devices via some form of transmission.
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1. Message: data. 2. Sender: The device that send the message.3. Receiver: The device that receive the message.4. Transmission Medium: The physical path between sender and receiver, the
message travel. 5. Protocol: Is a set of rules that governs data communication. It represents an
agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating.
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ReceiverSender
Message
Rules…
ProtocolTransmission Medium Rules…
Protocol
Data Communication ModesSimplex: In simplex mode, data can flow in
only one direction.
Always one side sender and another side receiver.
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Remote Control
TV
Data Communication Modes cont.Half-Duplex: In half-duplex mode, data can
flow in both directions but only in one direction at a time.
Walki-Talki
Each side maybe sender or receiver but not a same time.
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In different time
© Engr Faraz Khan www.tuf.edu.pk
Data Flow in Communication cont.Duplex: two-way concurrent. Computer network
Mobile Network
Each side sender and receiver at same time.
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At same time
© Engr Faraz Khan www.tuf.edu.pk
Network Classification Upon the transmission medium (type of connection):- 1. Point-to-point: A pair of nodes connected together via
dedicated link.
2. Multipoint: Number of node connected and share a single link.
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PC PCLink
PCPCPC
Link© Engr Faraz Khan www.tuf.edu.pk
Communication ChannelsCommunication channel is a connection between transmitter
and receiver through which Data can be transmitted. Communication channel also called as communication media
or transmission media
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Types of Communication channel
Twisted pair
Coaxial cable
Optical fiber
Satellite microwave
Terrestrial microwave
Broadcast radio
• Other types are Under Water Acoustic Channels, Storage Channels like magnetic tapes, magnetic disks etc.
Twisted-pair cable
One of the wires carries signal, the other is used only as a ground reference.
Number of twists per unit length determines the quality of the cable.
Coaxial cable
• Used for both analog and digital signals
• Effectively used at higher data rate and higher bandwidth
• For analog signals need amplifiers every few km
• For digital signals requires repeater every 1km
Optical fiberIts a flexible, transparent fiber made of high
quality glass (silica) or plastic, slightly thicker than a human hair. It can function as a waveguide, or “light pipe”, to transmit light between the two ends of the fiber
Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communication.
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Unguided Media (wireless communication medium)Terrestial MicrowaveSatellite CommunicationBroadcast RadioInfrared
© Engr Faraz Khan www.tuf.edu.pk 15
Terrestrial microwaveRequires fewer repeatersUse a parabolic dish to focus a
narrow beam.1-40GHz frequenciesUsed in Mobile communication
Satellite communicationReceive on one frequency, and
transmits on another frequencyeg. uplink 5.925-6.425 GHz &
downlink 3.7-4.2 GHz• Height 35,784km• Spaced at least 3-4° apart
Broadcast RadioRadio frequency range is 3kHz to 300GHzUse broadcast radio of 30MHz - 1GHz, for:
FM radioUHF and VHF television
Is a unidirectionalSuffers from multipath interference
Reflections from land, water, other objectsAre used for multicasts communications, such as radio and
television, and paging system.
Infrared CommunicationThis is one of the earliest types of optical
communication and is still very much in use today.It is found in remote controls for televisions, DVD
players and most entertainment devices.Infrared uses light that is invisible to us and is just
above the red end of the color spectrum.The key component of an infrared system is an
infrared LED to emit light and a photodiode in the television or equipment to receive the light.
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What is a Communication Protocol?
A Protocol is a set of rule that governs data communication.For two entities to communicate successfully, they must “speak
the same language”.What is communicated, how it is communicated, and when it is
communicated must conform.These conventions are referred to as a protocol.
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