Using Information Technology Chapter 7 Telecommunications

2 Telecommunications Networks & Communications--The “New Story” in Computing 7.1From the Analog to the Digital Age 7.2The Practical Uses of Communications 7.3Communications Channels: The Conduits of Communications 7.4Factors Affecting How Data Is Transmitted.

Telecommunications 3 Networks & Communications--The “New Story” in Computing 7.5Networks 7.6The Future of Communications 7.7Cyberethics: Controversial Material, Privacy, & Intellectual Property

Telecommunications 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

Telecommunications 5 Purpose of the Modem: Converting Digital Signals to Analog Signals & Back Sending modem - modulates digital signals into analog signals for transmission over phone lines Receiving modem - demodulates the analog signals back into digital signals Modem - short for modulate/demodulate

Telecommunications The Practical Uses of Communications Videoconferencing & VideophonesVideophones 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

Telecommunications 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

Telecommunications 8 Telecommuting Telecommuting - working at home while in telecommunication with the office

Telecommunications 9 Virtual Offices Virtual office - an often nonpermanent and mobile office run with computer and communications technology

Telecommunications 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

Telecommunications 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

Telecommunications 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

Telecommunications 13 The Electromagnetic Spectrum, the Radio Spectrum, & Bandwidth Radio frequency spectrum

Telecommunications 14 Wired Communications Channels Twisted-pair wire - two strands of insulated copper wire, twisted around each other

Telecommunications 15 Wired Communications Channels Coaxial cable - insulated copper wire wrapped in a solid or braided metal shield, then in an external cover

Telecommunications 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

Telecommunications 17 Wireless Communications Channels Infrared transmission - the transmission of data signals using infrared-light waves

Telecommunications 18 Wireless Communications Channels Broadcast radio - a wireless transmission medium that sends data over long distances-- between regions, states, or countries Microwave radio - transmits voice & data through the atmosphere as super-high-frequency radio waves called microwaves

Telecommunications 19 Wireless Communications Channels Communications satellites - microwave relay stations in orbit around the earth

Telecommunications 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 locationsGPS

Telecommunications 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 composition & sending Messages to other pagers

Telecommunications 22 Long-Distance Wireless Communications Analog cellular phones - designed primarily for communicating by voice through a system of ground-area cells Cell - hexagonal shape, usually 8 miles or less in diameter, & served by a transmitter-receiving tower

Telecommunications 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

Telecommunications 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

Telecommunications 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

Telecommunications 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

Telecommunications 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

Telecommunications 28 Factors Affecting How Data Is Transmitted Serial vs. parallel transmission Serial data transmission - bits are transmitted sequentially, one after the other

Telecommunications 29 Factors Affecting How Data Is Transmitted Serial vs. parallel transmission Parallel data transmission - bits are transmitted through separate lines simultaneously

Telecommunications 30 Factors Affecting How Data Is Transmitted Direction of transmission: simplex, half-duplex, & full-duplex Simplex transmission - data can travel in only one direction

Telecommunications 31 Factors Affecting How Data Is Transmitted Direction of transmission: simplex, half-duplex, & full-duplex Half-duplex transmission - data travels in both directions but only in one direction at a time

Telecommunications 32 Factors Affecting How Data Is Transmitted Direction of transmission: simplex, half-duplex, & full-duplex Full-duplex transmission - data is transmitted back and forth at the same time

Telecommunications 33 Factors Affecting How Data Is Transmitted Asynchronous transmission - data is sent one byte at a time, with each string of bits making up the byte bracketed with special control bits Transmission mode: asynchronous vs. synchronous

Telecommunications 34 Factors Affecting How Data Is Transmitted Synchronous transmission - data is sent in blocks, with start and stop bit patterns (synch bytes) at the beginning and end of the blocks Transmission mode: asynchronous vs. synchronous

Telecommunications 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

Telecommunications 36 Factors Affecting How Data Is Transmitted Multiplexers Concentrators Front-end processors Multiplexing - transmission of multiple signals over a single communications channel

Telecommunications 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

Telecommunications Networks Benefits of networks: Sharing of peripheral devices Sharing of programs and data Better communications Security of information Access to databases

Telecommunications 39 Types of Networks Wide area network (WAN) - a communications network that covers a wide geographical area, such as a country or the world

Telecommunications 40 Types of Networks Metropolitan area network (MAN) - a communications network covering a city or a suburbMAN Local area network (LAN) - connects computers and devices in a limited geographical area

Telecommunications 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

Telecommunications 42 Types of LANs Client/server LAN: Clients - microcomputers that request data; and Server - a powerful microcomputer that manages shared devices

Telecommunications 43 Types of LANs Peer-to-peer LAN - all microcomputers on the network communicate directly with one another without relying on a server

Telecommunications 44 Components of LANs Connection or cabling system Microcomputers with network interface cards Network OS Other shared devices Routers, bridges, and gateways

Telecommunications 45 Topology of LANs Star network - one in which all microcomputers and other communications devices are connected to a central server

Telecommunications 46 Topology of LANs Ring network - one in which all microcomputers and other communications devices are connected in a continuous loop

Telecommunications 47 Topology of LANs Bus network - one in which all communications devices are connected to a common channel

Telecommunications 48 Intranets, Extranets, & Firewalls IntranetIntranet - 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

Telecommunications The Future of Communications Satellite-based systems Beyond 3G to 4G Photonics: optical technologies at warp speed

Telecommunications Cyberethics Controversial material & censorship: Blocking software Browsers with ratings The V-Chip

Telecommunications 51 Cyberethics Privacy - the right of people not to reveal information about themselves CookieCookie - a file that the web server stores on your hard-disk drive when you visit a website