Computers Are Your Future Tenth Edition

Transcription

1 Computers Are Your Future Tenth Edition Chapter 3: Wired & Wireless Communication Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 1 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 2 Wired & Wireless Communication Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 3 1

2 What You Will Learn Define bandwidth and discuss the bandwidth needs of typical users Discuss how modems transform digital computer signals into analog signals List transmission media and explain several transmission methods Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 4 What You Will Learn Explain the limitations of the public switched telephone network (PSTN) for sending and receiving computer data. Describe multiplexing and digital telephony, including their impact on line usage. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 5 What You Will Learn Provide examples of how digitization and convergence are blurring the boundaries that distinguish popular p communications devices, including phones and computers. Discuss a variety of wired and wireless applications. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 6 2

3 Moving Data: Bandwidth and Modems Communications is the method of sending and receiving messages electronically between two points. Communication channels are the paths through which messages are passed from one location to another. Communication occurs over communication channels. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 7 Moving Data: Bandwidth and Modems Data movement over communication channels is performed through analog and digital signals. Analog signals obtain and translate data into continuous waveforms. Digital signals change data into discrete, discontinuous pulses. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 8 Moving Data: Bandwidth and Modems Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 9 3

4 Moving Data: Bandwidth and Modems The maximum amount of data transmitted through a communication channel is referred to as bandwidth. Broadband is any transmission medium transporting large amounts of data at high speeds. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 10 Moving Data: Bandwidth and Modems Communication devices that enable data transmission over telephone lines are known as modems. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 11 Moving Data: Bandwidth and Modems Modulation is the transformation of digital signals into analog signals. Demodulation is the transformation of analog signals into digital signals. The data transfer rate, the rate at which two modems exchange data, is measured in bits per second (bps). Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 12 4

5 Transmission Media Wired transmission media use solid forms, such as twisted-pair, coaxial, and fiber-optic cables, to transmit data. Wireless transmission media send data through the air or space by means of infrared, radio, or microwave signals. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 13 Transmission Media Twisted-pair cables transmit data using four insulated twisted wires that shield against electromagnetic interference. Coaxial cables transmit data and consist of a center copper wire surrounded by a layer of braided wire. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 14 Transmission Media Fiber-optic cable is made up of thin strands of glass or plastic that carry data through pulses of light. The infrared wireless transmission medium carries data through the air using light beams. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 15 5

6 Transmission Media Radio transmissions enable data in such forms as music, photos, and voice conversations to travel through the air as radio frequency or radio waves. Bluetooth is a short-range radio transmission technology that enables devices within 30 feet of each other to communicate wirelessly. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 16 Transmission Media Microwaves transmit data and are high-frequency electro-magnetic radio waves with very short frequencies. Satellites are microwave relay stations in space that transmit data through microwave signals to and from Earth-based stations. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 17 Transmission Media Direct Broadcast Satellite (DBS) is a consumer satellite technology that receives digital TV signals through the use of a reception dish. Computer systems using wireless transmission media require devices for communication called network access points. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 18 6

7 Wired Communication via the The public switched telephone network (PSTN), a worldwide telephone system, is an immense network used for data and voice communications. A subscriber loop carrier (SLC) is a curbside installation that connects subscribers. A local loop is the area served by an SLC. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 19 Wired Communication via the Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 20 Wired Communication via the Multiplexing is a technique that enables sending more than one call over an individual line. Last-mile technologies provide solutions for bottlenecks that result from the inability of users to access the PSTN s high-speed fiber-optic cables. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 21 7

8 Wired Communication via the Integrated Services Digital ing (ISDN) is the standard that makes digital telephone and data service available. Connecting computers to ISDN lines requires an ISDN adapter/digital modem. With ISDN, there is no extended dial-in or connection delay. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 22 Wired Communication via the Digital Subscriber Line (DSL) is the broad term for a group of technologies that offer high-speed access to the Internet. A DSL modem is required to modulate and demodulate analog and digital signals. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 23 Wired Communication via the Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 24 8

9 Wired Communication via the A cable modem is a tool that gives a computer the ability to access the Internet through cable TV connections. Leased lines enable continuous endto-end communication between two points through specially conditioned telephone lines, such as T1 lines. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 25 Wired Communication via the Last-mile technologies include: ISDN and DSL Cable modems and leased lines T3 lines Synchronous Optical (SONET) Multichannel Multipoint Distribution Service (MMDS) Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 26 Convergence: Is It a Phone or a Computer? Digitization is the process of transforming data into a digital form. Convergence means two things in IT: The blending of multiple industries such as computers, consumer electronics, and telecommunications The blending of products such as personal computers and telephones Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 27 9

10 Convergence: Is It a Phone or a Computer? Cellular telephones, originally analog devices, are digital devices that use radio signals to transmit voice, image, text, and video data. Cells are the limited geographic areas through which signals are transmitted. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 28 Convergence: Is It a Phone or a Computer? Each cellular network includes multiple mobile switching centers (MSCs) that control communication within a set of cells. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 29 Convergence: Is It a Phone or a Computer? A Personal Communication Service (PCS) is a group of related digital cellular technologies that has rapidly replaced the majority of analog cellular services. Digital cellular technologies use convergence to make smartphones, which combine the features of phones and computing devices. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 30 10

11 Convergence: Is It a Phone or a Computer? Digital phones resolve some of the problems of analog telephones by: Reducing signal interference Increasing reception Enhancing protection from eavesdropping Making it more difficult to commit cell phone fraud Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 31 Convergence: Is It a Phone or a Computer? Web-enabled devices display and respond to markup languages, such as HTML or XML, that are used to build Web pages. Examples include: PDAs Smartphones Notebooks Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 32 Internet telephony, aka VoIP (Voice over Internet Protocol), uses the Internet for real-time voice communication. VoIP service providers offer computerto-phone and phone-to-phone services for long-distance transmission through the Internet. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 33 11

12 Videoconferencing transmits sound and video images to people in different locations through digital video technology. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 34 Facsimile transmission (fax) makes it possible to transmit images of documents over telephone lines or the Internet. A computerized version of a standalone fax machine is known as a fax modem, which enables a computer to perform as a fax machine. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 35 Satellite technology is used for: Air navigation TV and radio broadcasting Paging Videoconferencing Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 36 12

13 Satellite radio is not affected by location, distance, or obstructions. Broadcasts of radio signals are sent through satellites orbiting the Earth. Use of satellites permits usage in areas with restricted local radio stations or bad AM/FM reception. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 37 Global Positioning System (GPS) is a system of 27 satellites that interact to allow users to obtain driving directions and numerous other types of information. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 38 Text messaging is comparable to receiving or transmitting small messages or instant messages through a cellular telephone. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 39 13

14 Picture messaging is the transmission of color pictures and backgrounds. The cellular telephone acts as a camera. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 40 What You ve Learned Bandwidth refers to the maximum data transfer capacity of a communication channel. Modems are used to modulate and demodulate data sent over dial-up phone lines. Communications involve both wired and wireless media. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 41 What You ve Learned Use of the public switched telephone network (PSTN), which is mostly digital, is decreasing because of the increase in the use of broadband alternatives. Multiplexing is the sending of multiple telephone calls or messages on a single line. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 42 14

15 What You ve Learned Digitization is the conversion of voice, text, graphic, audio, and video data into a digital format. Convergence is the merging of products like phones and computers Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 43 What You ve Learned Traditional wired technology can be used for VoIP and faxing, while wireless technology makes text and picture messages, satellite radios, and GPS services possible. Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 44 15