Priprincipl telecommunications and networks es learning objectivesnciples learning objectivesprincipidentify and describe the fundamental components of a telecommunications system6
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Priprincipl telecommunications and networks es learning objectivesnciples learning objectivesprincipidentify and describe the fundamental components of a telecommunications system6

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  • 1. Telecommunications and Networks LEARNING OBJECTIVES Identify and describe the fundamental components of a telecommunications system. ■ Identify two broad categories of telecommunications media and their associated characteristics. ■ Identify several telecommunications hardware devices and discuss their functions. ■ Telecommunications, networks, and their associated applications are essential to organizational success. ■ Describe the benefits associated with the use of a network. ■ Name three distributed processing alternatives and discuss their basic features. ■ List and describe several telecommunications applications that organizations benefit from today. Princple A telecommunications system and network have many fundamental components. Telecommunications, networks, and their associated applications are essential to organizational success Why Learn About Why Learn About Telecommunications and
  • 2. Networks?Telecommunications and Networks? Effective communication is essential to the success of every major human undertaking, from building great cities to waging war to running a modern organization. Today we use electronic messaging and networking to shrink the world and enable people everywhere to communicate and interact effectively without requiring facetoface meetings. Regardless of your chosen major or future career field, you will need the communications capabilities provided by telecommunications and networks, especially if your work involves the supply chain. Among all business functions, supply chain management might use telecommunications and networks the most because it requires cooperation and communications among workers in inbound logistics, warehouse and storage, production, finished product storage, outbound logistics, and most important, with customers, suppliers, and shippers. All members of the supply chain must work together effectively to increase the value perceived by the customer, so partners must communicate well. Other employees in human resources, finance, research and development, marketing, and sales positions must also use communications technology to communicate with people inside and outside the organization. To be a successful member of any organization, you must be able to take advantage of the capabilities that these technologies offer you. This chapter begins by discussing the importance of effective communications. Elements of a Telecommunications System Telecommunications devices relay signals between computer systems and transmission media. Sending computer system and equipment (1) Telecommunications Medium (4) Receiving computer
  • 3. system and equipment (6) Telecommunications device (5) Signal (2) device (3) AN OVERVIEW OF TELECOMMUNICATIONS telecommunications medium Any material substance that carries an electronic signal and serves as an interface between a sending device and a receiving device. telecommunications protocol A set of rules that governs the exchange of information over a communications medium. synchronous communications A form of communications where the receiver gets the message instantaneously, when it is sent. asynchronous communications A form of communications where the receiver gets the message after some delay—sometimes hours or
  • 4. days after the message is sent. Basic Telecommunications Channel Characteristics simplex channel A communications channel that can transmit data in only one direction. half-duplex channel A communications channel that can transmit data in either direction, but not simultaneously. full-duplex channel A communications channel that permits data transmission in both directions at the same time, so a full-duplex channel is like two simplex channels channel bandwidth The rate at which data is exchanged over a telecommunications channel, usually measured in bits per second (bps). broadband communications A telecommunications system in which a very high rate of data exchange is possible.
  • 5. Telecommunications Media Guided Transmission Media Types Media Type Description Advantages Disadvantages Twisted-pair wire Twisted pairs of copper wire, shielded or unshielded Used for telephone service; widely available Transmission speed and distance limitations Coaxial cable Inner conductor wire surrounded by insulation Cleaner and faster data transmission than twisted-pair wire More expensive than twisted-pair wire Fiber-optic cable Many extremely thin strands of glass bound together in a sheathing; uses light beams to transmit signals Diameter of cable is much smaller than coaxial; less distortion of signal; capable of high transmission rates
  • 6. Expensive to purchase and install Broadband over power lines Data is transmitted over standard highvoltage power lines Can provide Internet service to rural areas where cable and phone service may be nonexistent Can be expensive and may interfere with ham radios and police and fire communications Wireless Communications Options Technology Description Advantages Disadvantages Radio frequency Range Operates in the 3KHz–300 MHz range Supports mobile users; costs are dropping Signal highly susceptible to Interception Microwave— terrestrial and satellite frequency range High-frequency radio signal (300 MHz–300 GHz) sent through atmosphere and Avoids cost and effort to lay cable or wires; capable of high-speed transmission Must have unobstructed line of sight between sender and receiver; transmission effective only for short distances
  • 7. Infrared frequency range Signals in the 300 GHz–400 THz frequency range sent through air as light waves Lets you move, remove, and install devices without expensive wiring Must have unobstructed line of sight between sender and receiver; transmission effective only for short distances Short Range Wireless Options Near Field Communication (NFC) A very short-range wireless connectivity technology designed for cell phones and credit cards. .. Bluetooth A wireless communications specification that describes how cell phones, computers, faxes, personal digital assistants, printers, and other electronic devices can be interconnected over distances of 10–30 feet at a rate of about 2 Mbps. ultra wideband (UWB) A wireless communications technology that transmits large amounts of digital data over short distances of up to 30 feet using a wide spectrum of frequency bands and very low power. infrared transmission A wireless communications technology that operates at a frequency of 300 GHz and above that requires line-of-sight transmission and operates over short distances— such as a few yards. Zigbee Zigbee is a form of wireless communications frequently used in security systems and heating and cooling control systems. Zigbee is a relatively low-cost technology and requires little power, which allows longer life with smaller batteries.
  • 8. Medium Range Wireless Options Wi-Fi is a wireless telecommunications technology brand owned by the Wi-Fi Alliance, which consists of about 300 technology companies including AT&T, Dell, Microsoft, Nokia, and Qualcomm. The alliance exists to improve the interoperability of wireless local area network products based on the IEEE 802.11 series of telecommunications standards. With a Wi-Fi wireless network, the user’s computer, smartphone, or personal digital assistant has a wireless adapter that translates data into a radio signal and transmits it using an antenna. A wireless access point, which consists of a transmitter with an antenna, receives the signal and decodes it. When receiving data, the wireless access point takes the information from the Internet, translates it into a radio signal, and sends it to the device’s wireless adapter. These devices typically come with built-in wireless transmitters and software to enable them to alert the user to the existence of a Wi-Fi network. The area covered by one or more interconnected wireless access points is called a ―hot spot.‖ Current Wi-Fi access points have a maximum range of about 300 feet outdoors and 100 feet within a dry-walled building. Wi-Fi has proven so popular that hot spots are popping up in places such as airports, coffee shops, college campuses, libraries, and restaurants. Wide Area Wireless Network Options Many solutions provide wide area network options including satellite and terrestrial microwave transmission, wireless mesh, 3G, 4G, and WiMAX. Microwave Transmission Microwave is a high-frequency (300 MHz–300 GHz) signal sent through the air (see Figure 6.4). Terrestrial (Earth-bound) microwaves are transmitted by line-of-sight devices, so that the line of sight between the transmitter and receiver must be unobstructed. Typically, microwave stations are placed in a series—one station receives a signal, amplifies it, and retransmits it to the next microwave transmission tower. Such stations can be located roughly 30 miles apart before the curvature of the Earth makes it impossible for the towers to ―see one another.‖ Microwave signals can carry thousands of channels at the same time. Microwave Communications Because they are line-of-sight transmission devices, microwave dishes are frequently placed in relatively high locations, such as atop mountains, towers, or tall buildings. A communications satellite also operates in the microwave frequency range (see Figure 6.5). The satellite receives the signal from the Earth station, amplifies the relatively weak signal, and then rebroadcasts it at a different frequency. The advantage of satellite communications is that it can receive and broadcast over large geographic regions. Such problems as the curvature of the Earth, mountains, and other structures that block the line-ofsight microwave transmission make satellites an attractive alternative. Geostationary, low earth orbit, and small mobile satellite stations are the most common forms of satellite communications Satellite Transmission
  • 9. Communications satellites are relay stations that receive signals from one Earth station and rebroadcast them to another. A geostationary satellite orbits the Earth directly over the equator, approximately 22,300 miles above the Earth so that it appears stationary. The U.S. National Weather Service relies on the Geostationary Operational Environmental Satellite program for weather imagery and quantitative data to support weather forecasting, severe storm tracking, and meteorological research. A low earth orbit (LEO) satellite system employs many satellites, each in an orbit at an altitude of less than 1,000 miles. The satellites are spaced so that, from any point on the Earth at any time, at least one satellite is on a line of sight. A very small aperture terminal (VSAT) is a satellite ground station with a dish antenna smaller than 3 meters in diameter. News organizations employ VSAT dishes that run on battery power to quickly establish communications and transmit news stories from remote locations. Many people are also investing in VSAT technology in their homes to receive TV and send and receive computer communications. wireless mesh A way to route communications between network nodes (computers or other devices) by allowing for continuous connections and reconfiguration around blocked paths by ―hopping‖ from node to node until a connection can be established. 3G Wireless Communications The International Telecommunications Union (ITU) established a single standard for cellular networks in 1999. The goal was to standardize future digital wireless communications and allow global roaming with a single handset. Called IMT-2000, now referred to as 3G, this standard provides for faster transmission speeds in the range of 2–4 Mbps. Originally, 3G was supposed to be a single, unified, worldwide standard, but the 3G standards effort split into several different standards. One standard is the Universal Mobile Telephone System (UMTS), which is the preferred solution for European countries that use Global System for Mobile (GSM) communications. GSM is the de facto wireless telephone standard in Europe with more than 120 million users worldwide in 120 countries. Another 3G-based standard is Code-Division Multiple Access (CDMA), which is used in Australia, Canada, China, India, Israel, Mexico, South Korea, the United States, and Venezuela. The wide variety of 3G cellular communications protocols can support many business applications. The challenge is to enable these protocols to intercommunicate and support fast, reliable, global wireless communications. 3G wireless communication is useful for business travelers, people on the go, and people who need to get or stay connected. Although Wi-Fi is an option, 3G is preferable to mobile users concerned about the availability, cost, and security associated with the use of public Wi-Fi networks. 4G Wireless Communications 4G stands for fourth-generation broadband mobile wireless, which is expected to deliver more advanced versions of enhanced multimedia, smooth streaming video, universal access, portability across all types of devices, and eventually, worldwide roaming capability. 4G will also provide increased data transmission rates in the 20–40 Mbps range. Pine Cellular, Pine Telephone, and Choctaw Electric are deploying Nortel 4G technology to provide homes and businesses in southeastern Oklahoma with reliable, wireless high-speed Internet. The network will provide low-cost, broad coverage and deliver wireless services to rural areas where construction of a wired network is less economical. The 4G services will be
  • 10. provided at no charge to the local police and fire departments and public schools.23 Worldwide Interoperability for Microwave Access (WiMAX) The common name for a set of IEEE 802.16 wireless metropolitan area network standards that support different types of communications access. Future Wireless Communications Developments digital signal A signal that represents bits. analog signal A variable signal continuous in both time and amplitude so that any small fluctuations in the signal are meaningful. NETWORKS AND DISTRIBUTED PROCESSING Network Types computer network The communications media, devices, and software needed to connect two or more computer systems or devices. personal area network (PAN) A network that supports the interconnection of information technology within a range of 33 feet or so. local area network (LAN) A network that connects computer systems and devices within a small area, such as an office, home, or several floors in a building metropolitan area network (MAN) A telecommunications network that connects users and their devices in a geographical area that spans a campus or city.
  • 11. wide area network (WAN) A telecommunications network that ties together large geographic regions. Basic Processing Alternatives centralized processing Processing alternative in which all processing occurs at a single location or facility. decentralized processing Processing alternative in which processing devices are placed at various remote locations. distributed processing Processing alternative in which computers are placed at remote locations but are connected to each other via a network File Server Systems Users can share data through file server computing, which allows authorized users to download entire files from certain computers designated as file servers. After downloading data to a local computer, a user can analyze, manipulate, format, and display data from the file (see client/server An architecture in which multiple computer platforms are dedicated to special functions such as database management, printing, communications, and program execution. Telecommunications and Networks | Chapter 6 239 register operations, gasoline pump monitoring, and merchandising. Telecommunications Hardware modem A telecommunications hardware device that converts (modulates and demodulates) communications signals so they can be transmitted over the communication media.
  • 12. multiplexer A device that combines data from multiple data sources into a single output signal that carries multiple channels, thus reducing the number of communications links needed and therefore, lowering telecommunications costs. front-end processor A special-purpose computer that manages communications to and from a computer system serving hundreds or even thousands of users. private branch exchange (PBX) A telephone switching exchange that serves a single organization. switch A telecommunications device that uses the physical device address in each incoming message on the network to determine to which output port it should forward the message to reach another device on the same network. bridge A telecommunications device that connects one LAN to another LAN using the same telecommunications protocol. router A telecommunications device that forwards data packets across two or more distinct networks toward their destinations, through a process known as routing. gateway A telecommunications device that serves as an entrance to another network. Telecommunications Software network operating system (NOS) Systems software that controls the computer systems and devices on a network and allows them to communicate with each other network-management software Software that enables a manager on a networked desktop to monitor the
  • 13. use of individual computers and shared hardware (such as printers), scan for viruses, and ensure compliance with software licenses Securing Data Transmission encryption The process of converting an original message into a form that can only be understood by the intended receiver. Securing Wireless Networks Wired equivalent privacy (WEP) An early attempt at securing wireless communications based on encryption using a 64- or 128-bit key that is not difficult for hackers to crack. Wi-Fi Protected Access (WPA) A security protocol that offers significantly improved protection over WEP. Other Encryption Methods Data Encryption Standard (DES) An early data encryption standard developed in the 1970s that uses a 56-bit private key algorithm. Advanced Encryption Standard (AES) An extremely strong data encryption standard sponsored by the National Institute of Standards and Technology based on a key size of 128 bits, 192 bits, or 256 bits Virtual Private Network (VPN) virtual private network (VPN) A private network that uses a public network (usually the Internet) to connect multiple remote locations.
  • 14. TC services and network Application A Typical Cellular Transmission Scenario Cellular phones operate using radio waves to provide two-way communications. Using a cellular car phone, the caller dials the number (1). The signal is sent from the car’s antenna to the low-powered cellular antenna located in that cell (2). The signal is sent to the regional cellular phone switching office, also called the mobile telephone switching office (MTSO) (3). The signal is switched to the local telephone company switching station closest to the call destination (4). Now integrated into the regular phone system, the call is switched to the number originally dialed (5), all without the need for operator assistance. digital subscriber line (DSL) A telecommunications service that delivers high-speed Internet access to homes and small businesses over the existing phone lines of the local telephone network. Voice over Internet Protocol (VoIP) A collection of technologies and communications protocols that enables your voice to be converted into packets of data that can be sent over a data network such as the Internet, a WAN or LAN. Linking Personal Computers to Mainframes and Networks voice mail Technology that enables users to send, receive, and store verbal messages for and from other people around the world. reverse 911 service A communications solution that delivers emergency notifications to users in a selected geographical area. voice-to-text service A service that captures voice mail messages, converts them to text, and sends them to an e-mail account.
  • 15. Home and Small Business Networks Small businesses and many families own more than one computer and look for ways to set up a simple network to share printers or an Internet connection; access shared files such as photos, MP3 audio files, spreadsheets, and documents on different machines; play games that support multiple concurrent players; and send the output of network-connected devices, such as a security camera or DVD player, to a computer. Electronic Document Distribution electronic document distribution A process that enables the sending and receiving of documents in a digital form without being printed (although printing is possible Call Centers A call center is a physical location where an organization handles customer and other telephone calls, usually with some amount of computer automation. Call centers are used by customer service organizations, telemarketing companies, computer product help desks, charitable and political campaign organizations, and any organization that uses the telephone to sell or support products and services. An automatic call distributor (ACD) is a telephone facility that manages incoming calls, handling them based on the number called and an associated database of instructions. Call centers frequently employ an ACD to validate callers, place outgoing calls, forward calls to the right party, allow callers to record messages, gather usage statistics, balance the workload of support personnel, and provide other services. Telecommuting and Virtual Workers and Workgroups telecommuting A work arrangement whereby employees work away from the office using personal computers and networks to communicate via e-mail with other workers and to pick up and deliver results. Videoconferencing videoconferencing A telecommunications system that combines video and phone call capabilities with data or document conferencing.
  • 16. Electronic Data Interchange electronic data interchange (EDI) An intercompany, application-toapplication communication of data in a standard format, permitting the recipient to perform a standard business transaction, such as processing purchase orders. Public Network Services public network services Systems that give personal computer users access to vast databases and other services, usually for an initial fee plus usage fees Electronic Funds Transfer electronic funds transfer (EFT) A system of transferring money from one bank account directly to another without any paper money changing hands. Distance Learning distance learning The use of telecommunications to extend the classroom. Shared Workspace shared workspace A common work area where authorized project members and colleagues can share documents, issues, models, schedules, spreadsheets, photos, and all forms of information to keep each other current on the status of projects or topics of common interest. Unified Communications unified communications A technology solution that provides a simple and consistent user experience across all types of communications such as instant messaging, fixed and mobile phone, e-mail, voice mail, and Web conferencing.
  • 17. Global Positioning System Applications The Global Positioning System (GPS) is a fully functional global navigation satellite system employing over two dozen satellites in orbit at roughly 12,500 miles above the Earth. The satellites transmit microwave signals so a GPS receiver can precisely determine their location, speed, direction, and time.65 To determine its position, a GPS receiver receives the signals from three or more GPS satellites and determines its exact distance from each satellite. It then uses these distances to triangulate its precise location in terms of latitude, longitude, and altitude. A GPS receiver must have a clear line of sight to the satellite to operate, so dense tree cover and buildings can keep it from operating. Specialized Systems and Services With millions of personal computers in businesses across the country, interest in specialized and regional information services is increasing. Specialized services, which can be expensive, include professional legal, patent, and technical information. For example, investment companies can use systems such as Quotron and Shark to get up-to-the-minute information on stocks, bonds, and other investments.