Management Information Systems

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Transcript Management Information Systems

Information Technology in
Business: Telecommunications
and Networks
1
Learning Objectives
• Explain why successful managers must be familiar
with telecommunications concepts and
terminology
• Describe the principles of communication within a
computer system and among computers
• Identify the major media and devices used in
telecommunications
2
Learning Objectives (Cont.)
• List and explain the functions of different network
layouts and the concept of protocols
• Explain how telecommunications can improve
operations in organizations
• Cite the latest developments in telecommunications
media and transmission speed
3
Telecommunications in Business
• Transmittal of data from one computer to another
over a distance
• Telecommunications has improved business in three
main ways:
– Better communication
– Higher efficiency
– Better distribution of data
4
Telecommunications in Daily Use
• Cellular Phones
• Videoconferences
• Voice Mail
• Facsimile
• Information Kiosks
• Pay at the Pump
5
Telecommunications in Daily Use
(Cont.)
• Easy Passing
• Web-Based Electronic Commerce
• Worldwide Peer-to-Peer File Sharing
– Napster, Gnutella, BearShare, Morpheus
– With directory
– Without directory
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Telecommunications in Daily Use
(Cont.)
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Data Communications
• Any transfer of data within a computer, between a
computer and another device, or between two
computers
• Parallel and Serial Data Communications
– Serial data transfer refers to transmitting data one bit at a time.
– Parallel means the device is capable of receiving more than one
bit at a time (that is, it receives several bits in parallel). Most
modern printers are parallel.
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Data Communications (Cont.)
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Communication Direction
• Simplex
– One-way in one direction
• Half-Duplex
– One-way in two directions
• Full-Duplex
– Two-way in two directions
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Communication Direction (Cont.)
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Error Detection
• Parity Check
– Error detection method
– Checks that no bits are added or deleted
during transmission
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Bandwidth and Media
• Communications medium
– Physical medium through which data can be
communicated
– Telephone lines, television cables
• Capacity
– Speed at which data are communicated
– Also called the transmission rate
– It is often called “bandwidth”
• Bandwidth is measured in bits per second (bps)
– The greater the capacity, the faster the transmission
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Bandwidth and Media (Cont.)
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Bandwidth and Media (Cont.)
• Bandwidth
– Narrowband is low speed
– Broadband has greater capacity
• Media
– A medium is any means by which data can be
transmitted
15
Transmission speed
• A medium’s capacity is determined by the range of
bits per second at which it can operate
• Baud is the number of signals per minute
– e.g. 300 bits per second = 300 baud
• Repeater receives and strengthens signals before
sending them on
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Transmission Speed (Cont.)
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Twisted Pair
• Telephone line made of a pair of copper wires
twisted to reduce electromagnetic interference
(EMI)
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Coaxial Cable
• Commonly used for cable television transmission
– More expensive than twisted pair
– Greater transmission rate than twisted pair
– Much less susceptible to EMI
19
Microwaves
• High-frequency, short radio-frequency (RF) waves
– Terrestrial microwave
– Satellite microwave
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Optical Fiber
• Fiber-optic technology uses light instead of
electricity to transmit data
–
–
–
–
–
SUPER CLEAR GLASS STRANDS
FAST, LIGHT, DURABLE
TRILLIONS OF BITS PER SECOND, FULL DUPLEX
EXPENSIVE, HARDER TO INSTALL
OFTEN USED AS BACKBONE OF NETWORKS
SIGNAL
LASER
CABLE
PHOTO
DETECTOR
SIGNAL
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Characteristics of Media
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Modulation
• Modification of a digital signal into an analog signal
• Demodulation
– Modification of an analog signal into a digital signal
• Modems
– Devices that modulate and demodulate signals
• Multiplexor - device that transmits multiple signals
over single medium
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Modulation (Cont.)
• Analog vs. Digital
– Analog: A continuous series of waves
– Digital: A series of discrete bits
00101110100111010010101011101111001000100001011110101101001110100100101100
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Modulation (Cont.)
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Modulation (Cont.)
Figure 6.9 Multiplexing
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Networks
• LANs (Local Area Networks)
– Networks within a building, or within a group of
adjacent buildings
• WANs (Wide Area Networks)
– Networks that cross organizational boundaries or
reach outside the company
• Value-added networks (VANs)
• Wireless communication
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Network Topology
• Physical layout of the nodes in a network
– Star
– Ring
– Bus
– Tree
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Network Topology
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Star Topology
Star topology: a central host
computer receives all messages
and then forwards the message to
the appropriate computer or
USER
device (e.g. printer) on the
network. In a star topology, all
communications must go through
the main computer, and this
topology is one of the oldest
types.
USER
HOST
USER
USER
Advantage: easy to expand the network by adding more computers.
This set-up is ideal when some information has to be centralized on
the host computer, and other computers on the network can
download that information from the host computer.
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Bus Topology
• A bus topology connects all computers on the network through a single
circuit such as fiber optics, twisted pair etc to a central channel. Signals
transmitted over the channel are called messages. This topology
transmits each message to all computers on the network, although only
the targeted device will respond to the message. Each device has an
address and each device forwards messages to the address of a given
device.
• Advantages:
– easy to add or remove devices from the network without affecting network
performance.
– if one of the devices on the network fails, the network is not affected.
• Disadvantage: network performance decreases as the number of
messages increases, because each device checks to see if the message is
for it, or for some other device. This topology is ideal for LAN’s and
for applications such as e-mail and file transfers.
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Ring Topology
• Ring Topology: network devices are connected to one
another in the shape of a closed loop, so that each device is
connected directly to two other devices, one on either side
of it (closed ring). This topology transmits a message to all
devices between the sending node and the receiving node.
Each computer communicates directly with any other
computer by specifying the address of the device; the
topology distributes processing and control functions among
all devices on the network. If a computer on the network
fails, the message is rerouted around it.
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Networking Hardware
• Network Interface Card
• Hub
• Switch
• Bridge
• Router
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Virtual Private Network
• A combination of private and public lines
• A link between a private network and the Internet
• “Virtual” refers to the illusion that the use is
accessing a private network directly
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Protocols
• Communication protocols
– Rules governing the communication between
computers or between computers and other
computer-related devices
• Network protocols
– Rules governing a network of devices
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Protocols (Cont.)
• LAN Protocols
– Polling
– Contention
– Token passing
• WAN Protocols
– OSI (Open Systems Interconnection)
• Standard protocol model
• Seven layers
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Protocols (Cont.)
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Switching Techniques
• Circuit Switching
– Message is communicated in its entirety from the
transmitting computer to the receiving computer
• Packet Switching
– Message is divided into packets of bytes and
transmitted via several nodes
– TCP/IP
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Switching Techniques (Cont.)
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The Changing Business
Environment
• Cellular Phones
• Teleconferencing
• Voice Mail
• Facsimile
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A Variety of Services
• Cable
• Digital Subscriber Line (DSL)
• T1 and T3 Lines
• Satellite
• Fixed Wireless
• Gigabit Ethernet
• Optical Carrier
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A Variety of Services (Cont.)
42
A Wireless Revolution
• Popular Wireless Technologies
• Would You Like Wi-Fi With That?
• Combining Technologies
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Wireless Technologies (Cont.)
44
Wireless Technologies (Cont.)
45
Ethical and Societal Issues
Telecommuting: Pros and Cons
• Pros
– Saves travel cost and time
– Decreases pollution
– May reduce unemployment.
– Productivity higher among telecommuters
46
Ethical and Societal Issues
Telecommuting: Pros and Cons
• Cons
– 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
• Restaurants
• Downtown business and industries
47
Summary
• Telecommunications concepts and terminology
• Communication within a computer system and
among computers
• Telecommunications media and devices
• Network layouts and protocols
• Telecommunications impact on operations
• Telecommunications developments and speed
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