Transcript Telecommunications

Telecommunications
Infsy 540
Dr. Ocker
Chapter 7:
Telecommunications, the Internet,
and Information System Architecture
First Edition
Foundations of Information Systems
Vladimir Zwass
Irwin/McGraw-Hill
© The McGraw-Hill Companies, Inc.., 1998
Telecommunications

What is telecommunications?
Telecommunications

communication of information by
electronic means, usually over some
distance
Telecommunications

need to understand the
– capabilities
– costs,
– benefits

of alternative communications
technologies and how to maximize their
benefits for their organizations
information superhighway



high-speed digital telecommunications
networks that are national or worldwide
in scope and accessible by the general
public
a web of high-speed digital telecomm.
networks delivering information,
education, and entertainment services
to offices and homes
virtually eliminates the barriers of time
and place
information superhighway

most well-known implementation of the
info. superhighway is the Internet
telecommunication system


collection of compatible hardware and
software arranged to communicate
information from one location to another
can transmit
–
–
–
–
text
graphic images
voice
video
Telecommunications
system components



1. computers to process info
2. terminals (or any input/output
devices) to send and receive data
3. communications channels – links by which data or voice are transmitted
between sending and receiving devices in
a network
Telecommunications
system components

4. communications processors provide support functions for data
transmission and reception;
– e.g. modems, multiplexes, controllers,
front-end processors

5. communications software - controls
input and output activities and manages
other functions of network
Functions of telecommunications
systems




transmission of information
establishes the interface between
sender and receiver
routes messages along most efficient
paths
performs processing of information to
ensure that the right message gets to
the right receiver
Functions of
telecommunications systems

performs editing of data
 checks for errors

converts messages from one speed to
another
 e.g. from speed of computer to speed of
communications line

controls flow of information
Protocols

telecomm. network contains diverse
hardware and software components that
need to work together to transmit
information
Protocols


different components in a network can
communicate by following a common
set of rules that allows them to “talk” to
each other
protocol - set of rules and procedures
that govern transmission between
components in a network
principal functions of protocols





to identify each device in the
communication path
to secure the attention of the other
device
to verify correct receipt of the
transmitted message
to verify that a message requires
retransmission because it cannot be
correctly interpreted
to perform recovery when errors occur
Types of signals:
analog and digital


information travels through a
telecommunications system in form of
electromagnetic signals
signals represented in 2 ways - analog
and digital
Types of signals:
analog and digital

analog signal - continuous waveform
that passes through a communications
medium
– used for voice communications

digital signal - discrete waveform that
transmits data coded into 2 discrete
states as 1-bits and 0-bits, which are
represented as on-off electrical
impulses
– used for data communications
Types of signals:
analog and digital


if a telecommunications system is set
up to process analog signals - a digital
signal cannot be processed without
some alterations
all digital signals must be translated into
analog signals before they can be
transmitted in an analog system
Modems


modem - modulate/demodulate
translates the digital signals of computer
into analog form for transmission over
ordinary telephone lines, or translates
analog signals back into digital form for
reception by a computer
Telecommunications over a
Telephone Line
Digital
Computer
Modem
Analog
Telephone Link
Digital
Modem
Computer
communication channels


means by which data are transmitted
from one device in a network to another
links by which data or voice are
transmitted between sending and
receiving devices in a network
Types of communications
channels

a channel can utilize different kinds of
telecomm. transmission media:
– twisted wire
– coaxial cable
– fiber optics
– terrestrial microwave
– satellite
– radio (wireless) transmission
twisted wire


pairs of twisted copper wires
phone lines
coaxial cable


thickly insulated copper wire
used for cable TV
fiber optic cable

consists of thousands of strands of clear
glass fiber
– thickness of human hair


fast, light, and durable
data transmitted as light impulses
Radio (wireless) transmission


sends signal through air or space
without any physical tether
e.g. cellular radio systems used for
mobile telephones
microwave



high-volume long-distance, point-topoint transmission
high-frequency radio signals are
transmitted through atmosphere from
one terrestrial transmission station to
another
transmission only in straight line
satellites


serve as relay stations for microwave
signals
use to transmit large amounts of data
over long distances
LANS (local area networks)

cover limited distance
– usually one building or several buildings in
close proximity



require their own communications
channels
allow orgs. to share hardware and
software
many applications require high-capacity
networks
– e.g. email, graphics, video conferencing
LANS

used to link PCs within a building to
share information and peripheral
devices
– e.g. laser printers
Servers


computer in a network that stores
various programs and data files for
users of a network; determines access
and availability in the network
contains the LANS’ network operating
system
– manages the server
– routes and manages communications on
the network
Gateway


network gateway - connects the LAN to
public networks (e.g. telephone
network, other corporate networks)
can connect dissimilar networks by
translating from one set of protocols to
another
LAN technology

consists of cabling
– twisted wire, coaxial, or fiber optic



or wireless technology
that link computers and software
to control LAN activities
main disadvantage of LAN

Inflexible
– need new wiring each time the LAN is
moved
Wide-area Networks

cover broad geographical distances
– ranging from several miles to across
continents


may consist of a variety of cable,
satellite, and microwave technologies
common carriers - licensed by
government to provide communications
services to public (e.g. AT&T, MCI)
Wide-area Networks


can consist of combination of switched and
dedicated lines
switched lines
– telephone lines that can be used for data
transmission
– call is routed or switched through paths to
destination

dedicated line
– continuously available for transmission
– can be leased or purchased from common carriers
A Wide Area Network
Mainframe
(Headquarters)
Minicomputer
(Division A)
LAN
Minicomputer
(Division B)
LAN
Minicomputer
(Division C)
...
Local Workstations
(Microcomputers and
Other Terminals)
Telecommunications Equipment
in a Wide Area Network
telecommunications for
competitive advantage


many of the strategic applications would
not be possible without
telecommunications
firms that fail to consider
telecommunication in their strategic
plans will fall behind
Applications
– email
– voice mail
– fax
– teleconferencing
– digital information services
– videoconferencing
– electronic data interchange (EDI)
Applications

digital information services
– obtain information from outside of the
company instantly
– e.g. stock prices, legal research, news
articles etc.

includes electronic bulletin boards
Applications

Teleconferencing
– allows groups of people to confer
simultaneously via telephone or
electronically (computer conferencing)

videoconferencing
– teleconferencing with a view
Applications

EDI - electronic data interchange
– direct computer-to-computer exchange
between two organizations of standard
business transaction documents such as
invoices, bills, purchase orders.

EDI saves money and time because
transactions can be transmitted from
one IS to another through telecomm.
Network
– eliminates printing and handling of paper at
one end and inputting of data at the other
The Internet & Electronic
Commerce
Internet


Global network of computer netwokrs
without a centralized control
the “information superhighway”
To connect to the Internet


Network has to send and receive data
packets using the TCP/IP protocol suite
serieis of routers forwards packets to
tehir destination
World-wide Web (WWW)



Software that organizes information on
the Internet into a network of
interrelated electronic documents
Web is a client/server system
collection of electronic sites stored on
thousands of servers all over the world
Electronic commerce


Sharing business information,
maintaining business relationships and
conducting business transactions by
means of telecommunications networks
doing business electronically
– replacing most of the paperwork and
telephone work with compouter-mediated
information and transaction exchange
intranets




Internal networks of web sites
set up on corporate LANS and WANs
separated from the public Internet by a
firewall
firewall prevents access from the
Internet but allows access to the
Internet