Download Management Information Systems

Information Technology
Telecommunications and Networks
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Learning Objectives
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When you finish this chapter, you will:
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Recognize why successful managers must be
familiar with telecommunications concepts and
terminology.
Know the principles of communication within a
computer system and among computers.
Be able to identify the major media and devices
that are used in telecommunications.
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Learning Objectives

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Be able to list and explain the functions of
different network layouts and the concept of
protocols.
Understand how telecommunications can
improve operations in organizations.
Know the latest developments in
telecommunications media and transmission
speeds.
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Telecommunications in Business
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Telecommunications
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Transmittal of data from one computer to
another over a distance
Telecommunications has improved
business in three main ways:
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Better communication
Higher efficiency
Better distribution of data
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What is Data Communications?
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Data Communications
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Any transfer of data within a computer,
between a computer and another
device, or between two computers
Two Basic Modes
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Parallel transmission
Serial transmission
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Communication Direction
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Three Modes of Communication
Between Devices
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Simplex
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Half-Duplex
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One-way in one direction
One-way in two directions
Full-Duplex
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Two-way in two directions
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Communication Direction
Figure 6.2 Simplex, half-duplex, and full-duplex communication
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Communication Direction
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Asynchronous Communication
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In asynchronous transmission, the devices are not
synchronized by any timing aids.
Advantage of asynchronous transmission
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Does not need sophisticated and expensive timing
hardware
Disadvantage of asynchronous transmission
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Overhead, time spent transmitting bits that are not a part
of the primary data
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Communication Modes
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Synchronous Communication
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In synchronous communication, data are
transmitted using timing devices.
Messages are transmitted in packets.
Advantage of synchronous communication
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Overhead in synchronous communication is significantly
smaller than in asynchronous communication.
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Communication Modes
Figure 6.4 Synchronous transmission
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Channels and Media
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Communication Channel
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Physical medium through which data can
be communicated.
Channel Capacity
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Narrow band
Broadband
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Channels and Media
Figure 6.5 Transmission speed measurement
unit
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Channels and Media
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Media
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A medium is any means by which data can be
transmitted.
Transmission speed
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A medium’s capacity is determined by the range
of bits per second at which it can operate.
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Channels and Media
Figure 6.6 Telecommunications transmission speeds of different media
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Channels and Media
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Twisted Pair
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Telephone line made of a pair of copper wires twisted to
reduce electromagnetic interference (EMI)
Coaxial Cable
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Commonly used for cable television transmission
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More expensive than twisted pair
Greater transmission rate than twisted pair
Much less susceptible to EMI
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Channels and Media
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Microwaves
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High-frequency, short radio-frequency (RF) waves
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Terrestrial microwave
Satellite microwave
Optical Fiber
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Fiber-optic technology uses light instead of
electricity to transmit data.
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Channels and Media
Figure 6.7 Characteristics of channel media
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Analog vs. Digital
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Analog signals
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A continuous series of waves
Digital signals
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A series of discrete bits
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Modulation
Modification of a digital signal into an
analog signal
 Demodulation
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Modification of an analog signal into a
digital signal
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Modulation
Figure 6.8 Signal modulation
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Modulation
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Amplitude Modulation (AM)
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Frequency Modulation (FM)
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Phase Modulation
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Modulation
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Modems
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Devices that modulate and demodulate
signals
Multiplexers
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Devices that allow several telephones or
computers to transmit data through a single
line
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Frequency division multiplexing
Time-division multiplexing
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Modulation
Figure 6.9 Multiplexing
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Modulation
Figure 6.10 Frequency division
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Networks
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LANs (Local Area Networks)
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Networks within a building, or within a group of
adjacent buildings
WANs (Wide Area Networks)
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Networks that cross organizational boundaries or
reach outside the company
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Value-added networks (VANs)
Wireless communication
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Networks
Figure 6.11
Where
wireless LANs
are a good
choice
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Networks
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Network Topology
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Physical layout of the nodes in a network
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Star
Ring
Bus
Tree
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Network Topology
Figure 6.12 Network topologies
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Protocols
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Communication protocols
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Rules governing the communication between
computers or between computers and other
computer-related devices
Network protocols
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Rules governing a network of devices
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Protocols
Figure 6.13 Some communications software allows a user to establish
protocols: bit rate, parity, number of data bits, stop bits, and a
handshake procedure.
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Protocols
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LAN Protocols
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Polling
Contention
Token passing
WAN Protocols
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OSI (Open Systems Interconnection)
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Standard protocol model
Seven layers
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Protocols
Figure 6.14 The seven layers of the OSI model
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Switching Techniques and Transfer
 Modes
Circuit Switching
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Message is communicated in its entirety from the
transmitting computer to the receiving computer
Packet Switching
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Message is divided into packets of bytes and
transmitted via several nodes
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The Changing Business
Environment
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Cellular Phones
Teleconferencing
Voice Mail
Facsimile
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Ethical and Societal Issues
Telecommuting: Pros and Cons
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Pros
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Saves travel cost and time
Decreases pollution
May reduce unemployment.
Productivity higher among telecommuters
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Ethical and Societal Issues
Telecommuting: Pros and Cons
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Cons
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Employers tend to pressure
telecommuters to work harder than
workers in the office.
No office to foster new social ties and
camaraderie.
May negatively impact some segments
of the economy
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Restaurants
Downtown business and industries
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