Alternatives and Sources of Data Transmission

7/28/2019 Alternatives and Sources of Data Transmission

1/16

Alternatives and Sourcesof Data Transmission


2/16

Data Transmission

The transportation of anykind of information, from

one place to another by

physical means.

In computer terminology,this means sending

streams of bits or bytes

from one location to

another location usingtechnologies such as

copper wire, fiber optics,

lasers, radio, or infrared

light.


3/16

Data Transmission

Data transmission

involves the

communication of digitalmessages between digital

devices. Signals are sent

via a network to external

devices, such as printersor other computers.


4/16

Example of Data Transmission

EmailsA form of data transfer very

popular because virtually

free, but not secure.

Its possibilities in terms oftransmission / reception are

limited to a few megabytes

(usually up to 5 megabytes

or exceptionally up to 10Megabytes).


5/16

The Data Communications Channel

A communications

channel is the medium

through which digital

information must pass. Same as line, link, or pipe

Requires special hardware

that transmits the digital

information betweencomputers


6/16

Transmission Channels

Transmission channels are pathways that transfer dataThree Transmission Modes used to exchange data:

1. Simplex

Data flows in only one direction from the

transmitter device to the receiver device2. Half-duplex

Half-duplex mode allows data to move in eitherdirection, but each device must take turns in using

the line3. Full-duplex mode

With full-duplex transmission, data can flow inboth directions simultaneously.


7/16

Transmission Channels

Three TransmissionModes used to

exchange data:

1. Simplex2. Half-duplex

3. Full-duplex mode


8/16

Transmission Media: Twisted-Pair Wire

Twisted-pair wirecontains two insulatedcopper wires twistedaround each other

One twisted-pair lineprovides POTS

Plain old telephoneservice: analog line that

permits voice serviceAnother service is DSL

Digital subscriber line


9/16

Transmission Media: Coaxial Cable

Coax: the cable in cabletelevision

Minimum signal

distortionHas a very wide pipe

Hundreds of times faster

than POTS

100 times faster than

ISDN

Need a cable modem


10/16

Transmission Media: Wireless

Communication

Carries data viamicrowave or radiosignals

Transmission is line-of-sight

Use transceivers/repeaterstations

Satellites Eliminates line-of-sight

limitation

Geosynchronous orbit setat 22,300 miles aboveearth


11/16

Transmission Media: Fiber Optic Cable

Carries data as laser-

generated pulses of light

Foundation transmission

medium for Internet

backbone

Better for data security

Future technology lookslike very big pipe


12/16

Controlling Transmissions over

Communications Channels

Communication protocols

Rules that govern the

way data are

transmitted

TCP/IP (Transmission

Control

Protocol/Internet)Protocol


13/16

Asynchronous and Synchronous

Asynchronous Transmission uses start and stop bits to signify the

beginning and end of a transmission.

The start and stop bits must be of oppositepolarity. This allows the receiver to recognize

when the second packet of information is

being sent.


14/16


15/16

Asynchronous Transmission

Synchronous Transmission

Low speed

Modem needed

Transmitted as needed

Start/stop bits used

High speed

Source and destination in

synch

No start/stop bits needed


16/16

Documents

Alternatives and Sources of Data Transmission