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

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 faceto-

face 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

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

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.

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

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

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.

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 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 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.

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.

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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.

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 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.

TC services and network Application