Transcript Chapter 6

Principles of Information
Systems
Eighth Edition
Chapter 6
Telecommunications and Networks
Principles and Learning Objectives
• Effective communications are essential to
organizational success
– Define the terms communications and
telecommunications and describe the components of
a telecommunications system
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Principles and Learning Objectives
(continued)
• Communications technology lets more people send
and receive all forms of information over greater
distances at a faster rate than ever before
– Identify two broad categories of communications
media and their associated characteristics
– Identify several communications hardware devices
and discuss their function
– Name three types of telecommunications carriers
and discuss the services they provide
– Describe many of the benefits associated with a
telecommunications network
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Principles and Learning Objectives
(continued)
• Communications technology lets more people send
and receive all forms of information over greater
distances at a faster rate than ever before
(continued)
– Define the term communications protocols and
identify several common ones
– Name three distributed processing alternatives and
discuss their basic features
– List and describe several telecommunications
applications that organizations benefit from today
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Why Learn About Telecommunications
and Networks?
• Need to access data wherever it resides
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Fast, reliable communications
Exchange messages
Upload/download data and software
Route business transactions
Connect to remote databases
Send output to printers
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An Overview Of Telecommunications
• Telecommunications: electronic transmission of
signals for communications
– Telephone, radio, and television
• Communications can be synchronous or
asynchronous
– Synchronous communications: receiver gets
message instantaneously
– Asynchronous communications: receiver gets
message after some delay
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An Overview Of Telecommunications
(continued)
Figure 6.1: Elements of a Telecommunications System
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Basic Communications Channel
Characteristics
• Communication channels can be classified as:
– Simplex channel: transmits data in only one
direction
– Half-duplex channel: transmits data in either
direction, but not simultaneously
– Full-duplex channel: permits data transmission in
both directions at the same time
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Channel Bandwidth
• Channel bandwidth: rate at which data is
exchanged over a communications channel
– Usually measured in bits per second (bps)
• Broadband communications:
telecommunications system in which a very high
rate of data exchange is possible
• Narrowband communications:
telecommunications system that supports a much
lower rate of data exchange than broadband
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Communications Media
• Guided transmission media: communications
signals guided along a solid medium
• Wireless media: communications signal broadcast
over airwaves as a form of electromagnetic
radiation
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Guided Transmission Media Types
Table 6.1: Guided Transmission Media Types
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Guided Transmission Media Types
(continued)
Table 6.2: Wireless Technologies
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Telecommunications Hardware
• Typical telephone line only accommodates an
analog signal (continuous, curving signal)
• Computers generate a digital signal representing
bits
• Modem: device that translates data from digital to
analog and analog to digital
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Telecommunications Hardware
(continued)
Figure 6.6: How a Modem Works
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Telecommunications Hardware
(continued)
• Multiplexer: device that encodes data from two or
more data sources onto a single communications
channel
– Reduces number of communications channels
needed
– Lowers telecommunications costs
• Front-end processors: special-purpose
computers that manage communications serving
hundreds or even thousands of users
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Services
• Telecommunications carriers organize
communications channels, networks, hardware,
software, people, and business procedures to
provide valuable communications services
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Digital Subscriber Line (DSL)
• Telecommunications technology that delivers highbandwidth information to homes and small
businesses over ordinary copper telephone wires
• Asymmetric DSL (ADSL): download speed is
three to four times faster than upload speed
• Symmetric DSL (SDSL): speed of receiving and
sending data is the same
– Does not allow you to use the phone at the same
time
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Digital Subscriber Line (DSL)
(continued)
Figure 6.8: Digital Subscriber Line (DSL)
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Wireless Telecommunications
• All major long-distance carriers offer wireless
telecommunications services
– Phone calls or Internet access
• Wireless data communications will be broadly
adopted when providers can offer business users
enough bandwidth and connectivity so that they
use wireless as their sole connection
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Networks and Distributed Processing
• Computer network: communications media,
devices, and software needed to connect two or
more computer systems and/or devices
• Network nodes: computers and devices on the
networks
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Network Types
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Personal area network (PAN)
Local area network (LAN)
Metropolitan area network (MAN)
Wide area network (WAN)
International networks
Mesh networking
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Network Types (continued)
Figure 6.11: Partial Mesh Network
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Distributed Processing
• Centralized processing: all processing occurs at
a single location or facility
• Decentralized processing: processing devices
are placed at various remote locations
• Distributed processing: computers are placed at
remote locations but are connected to each other
via a network
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Client/Server Systems
• Client/server: multiple computer platforms are
dedicated to special functions such as database
management, printing, communications, and
program execution
– Each server is accessible by all computers on the
network
– A client is any computer that sends messages
requesting services from servers on the network
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Client/Server Systems (continued)
Figure 6.13: Client/Server Connection
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Communications Software and
Protocols
• Communications protocol: set of rules that
governs the exchange of information over a
communications channel
• ATM
• Frame relay
• IEEE 802.3 (Ethernet)
• T-carrier system
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Communications Software and
Protocols (continued)
Table 6.4: Common Telecommunications Protocols
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Wireless Communications Protocols
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Wi-Fi
WiMAX
Smart antenna technology
Ultra Wideband (UWB)
3G wireless communication
4G wireless communications
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Wireless Communications Protocols
(continued)
Table 6.14: Wi-Fi Network
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Wireless Communications Protocols
(continued)
• Switch: uses physical device address in each
incoming message to forward message to another
device on the same network
• Bridge: connects one LAN to another LAN that
uses the same telecommunications protocol
• Router: forwards data packets across two or more
distinct networks toward their destinations through
routing
• Gateway: serves as an entrance to another
network
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Communications Software
• Network operating system (NOS): systems
software that controls computer systems and
devices on a network and allows them to
communicate with each other
• Network-management software
– Monitors the use of individual computers and shared
hardware
– Scans for viruses
– Ensures compliance with software licenses
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Telecommunications and Network
Applications
• Telecommunications and networks are a vital part
of today’s information systems
• In some industries, telecommunications is virtually
a requirement for doing business
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Linking Personal Computers to
Mainframes and Networks
• Personal computers can be connected to
mainframe computers so that data can be
downloaded or uploaded
– Example: user can download a file from a database
to a personal computer
• Unattended systems: communications software
programs that instruct the computer to connect to
another computer on the network, download or
send information, and then disconnect from the
telecommunications line
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Voice Mail
• Users can send, receive, and store verbal
messages for and from other people around the
world
• Call management systems can be linked to
corporate e-mail and instant messaging systems
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Home and Small Business Networks
• Simple networks can be used to share printers or
an Internet connection, access files on different
machines, etc.
• Wireless network
– 802.11n access point
– Combined router, firewall, Ethernet hub, and
wireless hub
• Configure computers to share printers and files
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Electronic Document Distribution
• Send and receive documents in a digital form
without printing them (although printing is possible)
– Much faster
– Saves paper
– Saves document storage space
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Call Centers
• Call center: physical location where an
organization handles customer and other telephone
calls
– Usually with some computer automation
• Automatic call distributor (ACD): telephone
facility that manages incoming calls
– Handles calls based on the called number and an
associated database of instructions
• National Do Not Call Registry
• Offshore call centers
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Telecommuting and Virtual Workers
and Workgroups
• Telecommuting: employees work away from the
office using computing devices and networks
– More effective workers
– Saves money on office and parking space and office
equipment
– Reduces traffic congestion and air pollution
• Some types of jobs are better suited for
telecommuting than others
• Telecommuters must work independently, manage
time well, and balance work and home life
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Videoconferencing
• Enables people to hold a conference by combining
voice, video, and audio transmission
– Reduces travel expenses and time
– Increases managerial effectiveness through faster
response to problems, access to more people, and
less duplication of effort in multiple sites
• Systems usually combine video and phone call
capabilities with data or document conferencing
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Electronic Data Interchange
• Intercompany, application-to-application
communication of data in a standard format
– Permits recipient to perform a standard business
transaction, such as processing purchase orders
– Follows standards and procedures that can process
output from one system directly as input to other
systems without human intervention
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Electronic Data Interchange
(continued)
Table 6.17: Two Approaches to Electronic Data Interchange
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Public Network Services
• Give personal computer users access to vast
databases, the Internet, and other services
– Usually an initial fee plus usage fees
– Fees are based on services used; can range from
under $15 to over $500 per month
• Providers of public network services include
Microsoft, America Online, and Prodigy
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Electronic Funds Transfer
• Electronic funds transfer (EFT)
– Transfers money from one bank account directly to
another without the use of paper money
• Wire transfer
– Fast, reliable means to move funds from one
account to another using one of three major wiretransfer networks
• Automated clearing house (ACH)
– Secure private network connecting all U.S. financial
institutions to each other through the Federal
Reserve Board or other ACH operators
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Distance Learning
• Use of telecommunications to extend the
classroom
– Instructors create course home pages on the
Internet
– Students access the course syllabus and instructor
notes on the Web page
– Student e-mail mailing lists allow students and the
instructor to e-mail one another
– Chat groups allow students to form “virtual teams”
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Team Collaboration Systems
• Microsoft Office Groove: example of software
designed to enable collaboration and
communication within small teams
– Allows you to set up shared workspaces among
employees and others outside your organization
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Specialized Systems and Services
• Increased interest in specialized and regional
information services
• Electronic bulletin board: message center that
displays messages in electronic form
– Regional, national, and international bulletin boards
• Global positioning systems (GPSs) provide
specialized telecommunications services
• Virtual workers: conduct business at any time and
place
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Summary
• Telecommunications: electronic transmission of
signals for communications, by such means as
telephone, radio, and television
• Guided transmission media types: twisted-pair wire,
coaxial cable, fiber-optic cable, and broadband
over power lines
• Wireless transmission types: microwave, radio, and
infrared
• Computer network: communications media,
devices, and software needed to connect two or
more computer systems and/or devices
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Summary (continued)
• Network types: personal area network (PAN), local
area network (LAN), metropolitan area network
(MAN), wide area network (WAN), international
networks, and mesh networking
• Client/server systems: multiple computer platforms
dedicated to special functions such as database
management, printing, communications, and
program execution
• Communications protocol: set of rules that governs
the exchange of information over a
communications channel
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Summary (continued)
• Examples of telecommunications and network
applications
– Linking personal computers to mainframes and
networks, voice mail, home and small business
networks, electronic document distribution, call
centers, telecommuting, videoconferencing,
electronic data interchange, public network services,
electronic funds transfer, distance learning, and
team collaboration systems
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