1 Information Technology Telecommunications and Networks

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Information Technology

Telecommunications and Networks

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Learning Objectives

When you finish this chapter, you will: 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

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 Telecommunications

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

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What is Data Communications?

Data Communications Any transfer of data within a computer,

between a computer and another device, or between two computers

Two Basic Modes Parallel transmission Serial transmission

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Communication Direction

Three Modes of Communication Between Devices 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

Figure 6.2 Simplex, half-duplex, and full-duplex communication

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Communication Direction

Asynchronous Communication In asynchronous transmission, the devices are not

synchronized by any timing aids. Advantage of asynchronous transmission

Does not need sophisticated and expensive timing hardware

Disadvantage of asynchronous transmission Overhead, time spent transmitting bits that are not a part

of the primary data

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Communication Modes

Synchronous Communication In synchronous communication, data are

transmitted using timing devices. Messages are transmitted in packets. Advantage of synchronous communication

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

Communication Channel Physical medium through which data can

be communicated. Channel Capacity

Narrow band Broadband

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Channels and Media

Figure 6.5 Transmission speed measurement unit

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Channels and Media

Media A medium is any means by which data can be

transmitted. Transmission speed

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

Twisted Pair Telephone line made of a pair of copper wires twisted to

reduce electromagnetic interference (EMI) Coaxial Cable

Commonly used for cable television transmission More expensive than twisted pair Greater transmission rate than twisted pair Much less susceptible to EMI

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Channels and Media

Microwaves High-frequency, short radio-frequency (RF) waves

Terrestrial microwave Satellite microwave

Optical Fiber 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

Analog signals A continuous series of waves

Digital signals A series of discrete bits

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Modulation

Modification of a digital signal into an analog signal

Demodulation Modification of an analog signal into a

digital signal

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Modulation

Figure 6.8 Signal modulation

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Modulation

Amplitude Modulation (AM)

Frequency Modulation (FM)

Phase Modulation

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Modulation

Modems Devices that modulate and demodulate

signals Multiplexers

Devices that allow several telephones or computers to transmit data through a single line 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

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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Networks

Figure 6.11 Where wireless LANs are a good choice

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Networks

Network Topology Physical layout of the nodes in a network

Star Ring Bus Tree

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Network Topology

Figure 6.12 Network topologies

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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

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

LAN Protocols Polling Contention Token passing

WAN Protocols OSI (Open Systems Interconnection)

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 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

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The Changing Business Environment

Cellular Phones Teleconferencing Voice Mail Facsimile

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Ethical and Societal IssuesTelecommuting: Pros and Cons Pros

Saves travel cost and time Decreases pollution May reduce unemployment. Productivity higher among telecommuters

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Ethical and Societal IssuesTelecommuting: 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