Using Information Technology

1. Using Information Technology Chapter 7 Telecommunications

2. TelecommunicationsNetworks & Communications--The “New Story” in Computing • 7.1 From the Analog to the Digital Age • 7.2 The Practical Uses of Communications • 7.3 Communications Channels: The Conduits of Communications • 7.4 Factors Affecting How Data Is Transmitted • . • . • . Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

3. Networks & Communications--The “New Story” in Computing • 7.5 Networks • 7.6 The Future of Communications • 7.7 Cyberethics: Controversial Material, Privacy, & Intellectual Property Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

4. 7.1 From the Analog to the Digital Age • Analog - continuous and varying in strength and/or quality • Digital - communications signals or information represented in a two-stat (binary) way Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

5. Purpose of the Modem: Converting Digital Signals to Analog Signals & Back Modem - short for modulate/demodulate • Sending modem - modulates digital signals into analog signals for transmission over phone lines Receiving modem - demodulates the analog signals back into digital signals Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

6. 7.2 The Practical Uses of CommunicationsVideoconferencing & Videophones • Videoconferencing - the use of television video and sound technology as well as computers to enable people in different locations to see, hear, and talk with one another Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

7. Workgroup Computing & Groupware • Workgroup computing - teams of co-workers use networks of microcomputers to share information and to cooperate on projects • Made possible by networks, microcomputers, & groupware Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

8. Telecommuting • Telecommuting - working at home while in telecommunication with the office Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

9. Virtual Offices • Virtual office - an often nonpermanent and mobile office run with computer and communications technology Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

10. Smart Television • Digital television (DTV) - uses a digital signal, or series of 0s and 1s • High-definition television (HDTV) - high-resolution type of DTV • Standard-definition television (SDTV) - allows broadcasters to transmit more information within the HDTV bandwidth Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

11. Other Practical Uses of Communications • Home network - LAN which allows all the personal computers under the same roof to share peripherals and a single modem and Internet service • Information/internet appliance - a device merging computing capabilities with communications gadgets • TV set-top boxes • Internet phones • PDAs Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

12. 7.3 Communications Channels: The Conduits of Communications • Communications channel - the path (physical medium) over which information travels in a telecommunications system from its source to its destination Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

13. The Electromagnetic Spectrum, the Radio Spectrum, & Bandwidth Radio frequency spectrum Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

14. Wired Communications Channels • Twisted-pair wire - two strands of insulated copper wire, twisted around each other Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

15. Wired Communications Channels • Coaxial cable - insulated copper wire wrapped in a solid or braided metal shield, then in an external cover Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

16. Wired Communications Channels • Fiber-optic cable - dozens or hundreds of thin strands of glass or plastic that transmit pulsating beams of light rather than electricity Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

17. Wireless Communications Channels • Infrared transmission - the transmission of data signals using infrared-light waves Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

18. Wireless Communications Channels Microwave radio - transmits voice & data through the atmosphere as super-high-frequency radio waves called microwaves • Broadcast radio - a wireless transmission medium that sends data over long distances--between regions, states, or countries Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

19. Wireless Communications Channels • Communications satellites - microwave relay stations in orbit around the earth Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

20. Long-Distance Wireless Communications • Global Positioning System (GPS) - a series of earth-orbiting satellites continuously transmitting timed radio signals that can be used to identify earth locations Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

21. Long-Distance Wireless Communications • Pagers - simple radio receivers that receive data (but not voice messages) sent from a special radio transmitter • One-way pagers • Two-way pagers (enhanced paging) • Acknowledgments from recipient to sender • Email composition & sending • Messages to other pagers Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

22. Long-Distance Wireless Communications Cell - hexagonal shape, usually 8 miles or less in diameter, & served by a transmitter-receiving tower • Analog cellular phones - designed primarily for communicating by voice through a system of ground-area cells Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

23. Long-Distance Wireless Communications • Digital wireless services (2G) - support digital cellphones & PDAs, using a network of cell towers to send voice communications & data over the airwaves in digital form • Broadband wireless digital services (3G) - “always on” technology which can quickly transmit video, still pictures, and music, along with offering better ways to tape into websites than today’s 2G wireless systems • 2.5G - compromise between 2G and 3G, which is an “always on” version of 2G technology Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

24. Short-Range Wireless Communications • Bluetooth - a short-range wireless digital standard aimed at linking cellphones, PDAs, computers, & peripherals up to distances of 30 feet • WiFI - a short-range wireless digital standard aimed at helping machines inside offices to communicate at high speeds and share Internet connections at distances up to 300 feet • HomeRF - a separate, incompatible standard designed to network up to 10 PCs & peripherals as far as 150 feet apart Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

25. Compression & Decompression: Putting More Data in Less Space • Compression - a method of removing repetitive elements from a file so that the file requires less storage space and therefore less time to transmit • Lossless vs. lossy • Standards • JPEG • MPEG Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

26. 7.4 Factors Affecting How Data Is Transmitted • Transmission rate - a function of two variables: • Frequency - the cycles of waves per second • Bandwidth - the range between the highest & lowest frequencies • Higher frequency => greater transmission rate • Larger bandwidth => greater transmission rate Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

27. Factors Affecting How Data Is Transmitted • Line configurations • Point-to-point line - directly connects the sending & receiving devices • Multipoint line - a single line that interconnects several communications devices to one computer Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

28. Factors Affecting How Data Is Transmitted • Serial vs. parallel transmission • Serial data transmission - bits are transmitted sequentially, one after the other Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

29. Factors Affecting How Data Is Transmitted Parallel data transmission - bits are transmitted through separate lines simultaneously • Serial vs. parallel transmission Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

30. Factors Affecting How Data Is Transmitted • Direction of transmission: simplex, half-duplex, & full-duplex • Simplex transmission - data can travel in only one direction Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

31. Factors Affecting How Data Is Transmitted Half-duplex transmission - data travels in both directions but only in one direction at a time • Direction of transmission: simplex, half-duplex, & full-duplex Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

32. Factors Affecting How Data Is Transmitted Full-duplex transmission - data is transmitted back and forth at the same time • Direction of transmission: simplex, half-duplex, & full-duplex Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

33. Factors Affecting How Data Is Transmitted Transmission mode: asynchronous vs. synchronous • Asynchronous transmission - data is sent one byte at a time, with each string of bits making up the byte bracketed with special control bits Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

34. Factors Affecting How Data Is Transmitted Transmission mode: asynchronous vs. synchronous • Synchronous transmission - data is sent in blocks, with start and stop bit patterns (synch bytes) at the beginning and end of the blocks Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

35. Factors Affecting How Data Is Transmitted • Circuit switching - transmitter has full use of the circuit until all the data has been transmitted and the circuit is terminated • Packet switching - electronic messages are divided into packets for transmission over a wide area network to their destination through the most expedient route Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

36. Factors Affecting How Data Is Transmitted Multiplexing - transmission of multiple signals over a single communications channel • Multiplexers • Concentrators • Front-end processors Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

37. Factors Affecting How Data Is Transmitted • Protocol - a set of conventions governing the exchange of data between hardware and/or software components in a communications network Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

38. 7.5 Networks • Benefits of networks: • Sharing of peripheral devices • Sharing of programs and data • Better communications • Security of information • Access to databases Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

39. Types of Networks • Wide area network (WAN) - a communications network that covers a wide geographical area, such as a country or the world Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

40. Types of Networks • Metropolitan area network (MAN) - a communications network covering a city or a suburb • Local area network (LAN) - connects computers and devices in a limited geographical area Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

41. Types of Networks • Host computer - a mainframe or midsize central computer that controls the network • Node - any device that is attached to a network • Backbone - a high-speed network that connects LANs and MANs to the Internet Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

42. Types of LANs • Client/server LAN: • Clients - microcomputers that request data; and • Server - a powerful microcomputer that manages shared devices Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

43. Types of LANs • Peer-to-peer LAN - all microcomputers on the network communicate directly with one another without relying on a server Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

44. Components of LANs • Connection or cabling system • Microcomputers with network interface cards • Network OS • Other shared devices • Routers, bridges, and gateways Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

45. Topology of LANs • Star network - one in which all microcomputers and other communications devices are connected to a central server Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

46. Topology of LANs • Ring network - one in which all microcomputers and other communications devices are connected in a continuous loop Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

47. Topology of LANs • Bus network - one in which all communications devices are connected to a common channel Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

48. Intranets, Extranets, & Firewalls • Intranet - an organization’s internal private network that uses the infrastructure and standards of the Internet and the WWW • Extranets - private intranets that connect not only internal personnel but also selected suppliers and other strategic parties • Firewalls - a system of hardware and software that blocks unauthorized users inside and outside the organization from entering the intranet Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

49. 7.6 The Future of Communications • Satellite-based systems • Beyond 3G to 4G • Photonics: optical technologies at warp speed Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.

50. 7.7 Cyberethics • Controversial material & censorship: • Blocking software • Browsers with ratings • The V-Chip Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.