--6InfoTech_Telecomm.ppt 736KB Mar 29 2010 04:55:11 AM

Information
Technology
Telecommunications and Networks

1

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.

2

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.

3

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
4

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

5

Communication Direction


Three Modes of Communication
Between Devices


Simplex




Half-Duplex




One-way in one direction
One-way in two directions

Full-Duplex


Two-way in two directions

6

Communication Direction

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

7

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

8

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.

9

Communication Modes

Figure 6.4 Synchronous transmission

10

Channels and Media


Communication Channel




Physical medium through which data can
be communicated.

Channel Capacity



Narrow band
Broadband

11

Channels and Media

Figure 6.5 Transmission speed measurement
unit

12

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.

13

Channels and Media

Figure 6.6 Telecommunications transmission speeds of different media

14

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

15

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.

16

Channels and Media

Figure 6.7 Characteristics of channel media

17

Analog vs. Digital


Analog signals




A continuous series of waves

Digital signals


A series of discrete bits

18

Modulation
Modification of a digital signal into an
analog signal
 Demodulation




Modification of an analog signal into a
digital signal

19

Modulation

Figure 6.8 Signal modulation

20

Modulation


Amplitude Modulation (AM)



Frequency Modulation (FM)



Phase Modulation

21

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
22

Modulation

Figure 6.9 Multiplexing

23

Modulation

Figure 6.10 Frequency division

24

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

25

Networks

Figure 6.11
Where
wireless LANs
are a good
choice

26

Networks


Network Topology


Physical layout of the nodes in a network





Star
Ring
Bus
Tree

27

Network Topology

Figure 6.12 Network topologies

28

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

29

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.

30

Protocols


LAN Protocols






Polling
Contention
Token passing

WAN Protocols


OSI (Open Systems Interconnection)



Standard protocol model
Seven layers

31

Protocols

Figure 6.14 The seven layers of the OSI model

32

Switching Techniques and
 Transfer
Circuit Switching
Modes




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

33

The Changing Business
Environment





Cellular Phones
Teleconferencing
Voice Mail
Facsimile

34



Ethical and Societal
Issues

Pros
Telecommuting: Pros and Cons





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

35

Ethical and Societal
Issues
Pros and Cons
Telecommuting:
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

36