Lecturer: Muhammad ShoaibOffice R-03, Amin Campus

faraz.khan@tuf.edu.pk041 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 RepresentationTextNumbersImagesAudioVideo

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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

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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

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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.

Guided MediaTwisted PairCoaxial Cable Fiber Optic

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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

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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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Thank You !

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