Chapter 8Telecommunications, Networks, and Wireless Computing 8-
Chapter 8
Telecommunications, Networks, and Wireless Computing
True-False Questions
When selecting appropriate technologies for enterprise networking, Internet technology, XML, and Java allow for maximum connectivity and application integration.
Answer:False Difficulty: Medium Reference: p. 266
The use of packet switching to increase telecommunications transmission efficiency is one of the three major developments that has shaped contemporary digital telecommunications systems.
Answer: True Difficulty: Medium Reference: p. 267
Public networking is the linking of separate networks, each of which retains its own identity, into an interconnected network.
Answer: False Difficulty: Medium Reference: p. 267
Message switching is a technology that breaks messages into small, fixed bundles of data and routes them in the most economical way through any available communications channel.
Answer:False Difficulty: Medium Reference: p. 268
Peer-to-peer networking has become the predominant model for corporate computing.
Answer: False Difficulty: Medium Reference: p. 268
The Internet is based on peer-to-peer networking.
Answer: False Difficulty: Medium Reference: p. 268
A data server is a specialized communications processor that forwards data from one network to another network.
Answer: False Difficulty: Medium Reference: p. 268
The X.25 packet switching standard uses packets of 128 bytes each.
Answer: True Difficulty: Easy Reference: p. 268
The OSI model is the dominant model for achieving connectivity among different networks, providing an agreed-on method for breaking up digital messages into packets, routing them to the proper addresses, and then reassembling them into coherent messages.
Answer: False Difficulty: Medium Reference: p. 269
The PDA connectivity model is the one used in the Internet.
Answer: False Difficulty: Medium Reference: p. 269
If two computers are based on different hardware and software platforms, they will not be able to communicate via TCP/IP.
Answer: False Difficulty: Medium Reference: p. 270
A digital signal is a continuous waveform.
Answer: False Difficulty: Easy Reference: p. 270
Until recently, fiber-optic cable was the least expensive medium for telecommunications.
Answer: False Difficulty: Easy Reference: p. 271
Optical networks can transmit voice, data, and video.
Answer: True Difficulty: Easy Reference: p. 271
Presently, a problem with optical transmission is that it must convert data back and forth to electrical signals.
Answer: True Difficulty: Medium Reference: p. 271
The electromagnetic spectrum is the wireless transmission medium.
Answer: True Difficulty: Medium Reference: p. 272
Infrared transmissions fall in a higher frequency range than microwave transmissions.
Answer: True Difficulty: Hard Reference: p. 272
Today paging devices can transmit short alphanumeric messages.
Answer: True Difficulty: Easy Reference: p. 273
Personal communication services are entirely digital.
Answer: True Difficulty: Hard Reference: p. 273
Mobile data networks are not explicitly designed for two-way transmissions of data files.
Answer: False Difficulty: Medium Reference: p. 274
Security is a problem for wireless transmission because it is easily intercepted.
Answer: True Difficulty: Easy Reference: p. 274
The bit rate is frequently smaller than the baud rate.
Answer: False Difficulty: Hard Reference: p. 274
Bandwidth is the highest frequency that the channel can accommodate.
Answer: False Difficulty: Medium Reference: p. 274
Ring and bus topologies are used in LANs.
Answer:True Difficulty: Easy Reference: p. 276
Switched lines are continuously available for transmission because they have been changed from voice lines to data lines.
Answer: False Difficulty: Hard Reference: p. 279
When using a value-added network, subscribers pay only for the amount of data they transmit plus a subscription fee.
Answer: True Difficulty: Easy Reference: p. 279
ATM parcels information into 8-byte cells, allowing data to be transmitted between computers from different vendors at high speeds.
Answer: True Difficulty: Medium Reference: p. 281
Basic rate ISDN can transmit data at a rate of 512 kilobits per second on an existing local telephone line.
Answer: False Difficulty: Hard Reference: p. 281
A digital subscriber line can operate over existing copper telephone lines and has a higher transmission capacity than ISDN.
Answer: True Difficulty: Easy Reference: p. 281
ADSL supports a transmission rate of 1.5 to 9 megabits per second when receiving data.
Answer: True Difficulty: Easy Reference: p. 281
Presently, a cable modem has stronger capabilities for receiving data than for sending data.
Answer: True Difficulty: Medium Reference: p. 281
A T1 line is a dedicated telephone connection of 24 channels.
Answer: True Difficulty: Medium Reference: p. 281
A T1 channel can be configured to carry either voice or data traffic.
Answer: True Difficulty: Easy Reference: p. 281
Cable modems provide high-speed transmission over cable TV lines and are shared by many users.
Answer: True Difficulty: Easy Reference: p. 281
A broadband medium can transmit multiple channels of data simultaneously.
Answer: True Difficulty: Medium Reference: p. 281
Communications companies and commercial on-line services offer electronic mail to their users.
Answer: True Difficulty: Easy Reference: p. 282
The ability of two or more people at distant locations to edit and modify the same document simultaneously is called teleconferencing.
Answer: False Difficulty: Easy Reference: p. 284
Digital learning refers to instruction delivered through purely digital technology, such as CD-ROMs, the Internet, or private networks.
Answer: False Difficulty: Medium Reference: p. 285
EDI allows computer-to-computer exchange of standardized documents between two organizations and lowers transaction costs.
Answer: True Difficulty: Easy Reference: p. 286
EDI differs from e-mail in that it transmits an actual structured transaction as opposed to an unstructured text message such as a letter.
Answer: True Difficulty: Medium Reference: p. 286
Multiple- Choice Questions
A collection of compatible hardware and software arranged to communication information from one location to another best describes:
a. telecommunication system.
b. legacy system.
c. corporate system.
d. communication system.
e. network operating system.
Answer: a Difficulty: MediumReference: p. 266
Various networks that are linked together to make information flow freely throughout different parts of the organization and between the organization and its external environment best describes:
a. internetworking.
b. enterprise networking.
c. cooperative networking.
d. extranet.
e. virtual private networking.
Answer: b Difficulty: MediumReference: p. 267
Which of the following is a technology that breaks messages into small, fixed bundles of data and routes them in the most economical way through any available communications channel?
a. ISDN
b. Dense wavelength division multiplexing
c. Packet switching
d. Time division multiplexing
e. TDMA
Answer: c Difficulty: MediumReference: p. 268
Which of the following is the connectivity model used in the Internet?
a. ISDN
b. DWDM
c. GSM
d. TCP/IP
e. OSI
Answer: d Difficulty: MediumReference: p. 269
Which of the following is not one of the TCP/IP layers?
a. Application layer
b. Presentation layer
c. Transportation layer
d. Internet layer
e. Network interface layer
Answer: b Difficulty: HardReference: p. 269
“Crosstalk” is:
a. two data communications on the same fiber-optic cable.
b. two computers of different architecture talking to each other.
c. interference with the signals on twisted wire media during high-speed transmission.
d. set up by protocols.
e. changing an analog signal to a digital one.
Answer: c Difficulty: MediumReference: p. 270
Optical networks transmit:
a. voice.
b. data
c. video.
d. using pulses of light.
e. All of the above
Answer: e Difficulty: EasyReference: p. 271
Fiber-optic cable consists of:
a. strands of clear glass fibers.
b. glass fibers wound with copper wire.
c. twisted pairs of glass fibers.
d. dedicated 10-megabit lines.
e. glass fibers transmitting an analog signal.
Answer: a Difficulty: EasyReference: p. 271
The part of a network that handles major traffic and provides the primary path for traffic flowing to or from other networks best describes:
a. bus.
b. switch.
c. backbone.
d. server.
e. node.
Answer: c Difficulty: MediumReference: p. 271
The ability of a single communications channel to carry data transmissions from multiple sources simultaneously best defines:
a. packet switching.
b. circuit switching.
c. parallel processing.
d. multiplexing.
e. baseband.
Answer: d Difficulty: MediumReference: p. 271
Technology for boosting transmission capacity of optical fiber by using many different wavelengths to carry separate streams of data over the same fiber strand at the same time best describes:
a. optical division multiplexing.
b. dense wavelength division multiplexing.
c. digital streamlined multiplexing.
d. broadband multiplexing.
e. Wi-Fi.
Answer: b Difficulty: HardReference: p. 271
DWDM uses:
a. infrared data transmission.
b. satellite transmissions.
c. different colors of light to carry different messages over the same strand at the same time.
d. differently-timed pulses of light to carry different messages over the same strand at the same time.
e. a single wavelength per strand.
Answer: c Difficulty: HardReference: p. 271
Common technologies for wireless data transmission include:
a. microwave transmission.
b. communication satellites.
c. pagers.
d. personal communication services.
e. All of the above
Answer: e Difficulty: EasyReference: p. 272
Microwave signals:
a. follow a straight line.
b. require the transmission stations be positioned 37 miles apart.
c. do not bend with the curvature of the earth.
d. are widely used for high-volume, long-distance, point-to-point communication.
e. All of the above
Answer: d Difficulty: EasyReference: p. 272
Communications satellites are:
a. relay stations for fiber-optic transmissions.
b. outside the electromagnetic spectrum.
c. used mainly by cell phones.
d. usually in very high orbits so they will not interfere with space stations.
e. cost effective for transmitting large quantities of data over very long distances.
Answer: e Difficulty: MediumReference: p. 272
In ascending order, the frequency ranges for communications media are:
a. radio, infrared, ultraviolet, visible light, X-ray, and gamma/cosmic.
b. X-ray, infrared, ultraviolet, microwave, visible light, and gamma/cosmic.
c. radio, microwave, infrared, visible light, ultraviolet light, X-ray, and gamma/cosmic.
d. gamma/cosmic, X-ray, visible light, ultraviolet, microwave, infrared, and radio.
e. radio, microwave, infrared, ultraviolet, visible light, X-ray, and gamma/cosmic.
Answer: c Difficulty: HardReference: p. 272
A wireless cellular technology that uses lower-power, higher-frequency radio waves than does cellular technology best defines:
a. personal digital assistants.
b. packet distribution networks.
c. paging system.
d. personal communications services.
e. mobile data networks.
Answer: d Difficulty: MediumReference: p. 273
Paging devices today can:
a. send and receive short alphanumeric messages.
b. send only analog signals.
c. send only digital signals.
d. be used over long distances with special microwave transmitters.
e. support groupware applications.
Answer: a Difficulty: EasyReference: p. 273
In a cell-phone network, each radio antenna cell normally covers:
a. a 30-mile area, overlapping with adjacent cells by about 5 miles.
b. radio and microwave transmissions, but not digital transmission.
c. only phones of the particular cell-phone service being used.
d. an eight-mile hexagonal cell.
e. line-of-sight to any other antenna.
Answer: d Difficulty: MediumReference: p. 273
PDAs:
a. have built-in wireless telecommunications capabilities.
b. are small, pen-based, handheld computers.
c. are capable of entirely digital transmission.
d. have work-organization software.
e. All of the above
Answer: e Difficulty: EasyReference: p. 273
Because wireless transmission can be easily intercepted:
a. it is not useful in digital environments.
b. security and privacy are more difficult.
c. it is best used for cable television.
d. even a radio can pick up the digital signal.
e. Both a and c
Answer: b Difficulty: EasyReference: p. 274
Data can be transmitted seamlessly between different wireless networks:
a. only over short distances.
b. only if they use compatible standards.
c. only over the Internet.
d. only with government permission.
e. only when cellular phones are used.
Answer: b Difficulty: HardReference: p. 274
At higher speeds, a single signal change:
a. can transmit several messages at once.
b. can transmit microwave frequencies.
c. can be measured only in hertz.
d. can transmit more than one bit at a time.
e. can decrease the baud rate.
Answer: d Difficulty: MediumReference: p. 274
A change in signal from positive to negative or vice versa that is used as a measure of transmission speed best defines:
a. baud.
b. bits per second.
c. multiplex.
d. digital differential.
e. transmission rate.
Answer: a Difficulty: MediumReference: p. 274
At its fastest, fiber-optic cable can transmit data at speeds of:
a. 1.544 megabits per second.
b. 1024 bits per second.
c. up to 2.56 megabits per second.
d. up to 6 terabits per second.
e. 1 terabit per second.
Answer: d Difficulty: MediumReference: p. 275
A star network is a:
a. network topology in which all computers and other devices are connected to a central hub.
b. network topology in which all computers are linked by a closed loop in a manner that passes data in one direction from one computer to another.
c. network topology linking a number of computers by a single circuit with all messages broadcast to the entire network.
d. network architecture that gives equal power to all computers on the network.
e. telecommunications network that spans a large geographical distance.
Answer: a Difficulty: MediumReference: p. 276
A ring network is a:
a. network topology in which all computers and other devices are connected to a central hub.
b. network topology in which all computers are linked by a closed loop in a manner that passes data in one direction from one computer to another.
c. network topology linking a number of computers by a single circuit with all messages broadcast to the entire network.
d. network architecture that gives equal power to all computers on the network.
e. telecommunications network that spans a large geographical distance.
Answer: b Difficulty: MediumReference: p. 276
Peer-to-peer is a:
a. network topology in which all computers and other devices are connected to a central hub.
b. network topology in which all computers are linked by a closed loop in a manner that passes data in one direction from one computer to another.
c. network topology linking a number of computers by a single circuit with all messages broadcast to the entire network.
d. network architecture that gives equal power to all computers on the network.
e. telecommunications network that spans a large geographical distance.
Answer: d Difficulty: MediumReference: p. 276
A bus network is a:
a. network topology in which all computers and other devices are connected to a central hub.
b. network topology in which all computers are linked by a closed loop in a manner that passes data in one direction from one computer to another.
c. network topology linking a number of computers by a single circuit with all messages broadcast to the entire network.
d. network architecture that gives equal power to all computers on the network.
e. telecommunications network that spans a large geographical distance.
Answer: c Difficulty: MediumReference: p. 276
The LAN network interface card:
a. specifies the data transmission rate.
b. specifies the size of the message units.
c. specifies the addressing information attached to each message.
d. specifies the network topology.
e. All of the above
Answer: e Difficulty: EasyReference: p. 276
Which of the following is the Wi-Fi mode where wireless devices communicate with a wired LAN via access points?
a. Peer mode
e. Multiplexed mode
Answer: d Difficulty: HardReference: p. 277
Which of the following is the Wi-Fi mode where wireless devices communicate with each other directly and do not use an access point?
a. Peer mode
b. Ad-hoc mode
c. Star mode
d. Infrastructure mode
e. Multiplexed mode
Answer: b Difficulty: HardReference: p. 277
Which of the following is a specific geographic location in which an access point provides public Wi-Fi network service?
a. Connect point
b. Peer point
c. Hot spot
d. Node location
e. Wi-Fi channel
Answer: c Difficulty: MediumReference: p. 278
A private, multipath, data-only, third-party-managed network that multiple organizations use on a subscription basis best describes:
a. local area network.
b. peer-to-peer network.
c. Wi-Fi network.
d. wide area network.
e. value-added network.
Answer: e Difficulty: MediumReference: p. 279
A networking technology that parcels information into 8-byte cells, allowing data to be transmitted between computers from different vendors at high speeds best describes:
a. broadband.
b. asynchronous transfer mode.
c. integrated services digital network.
d. converged network.
e. star network.
Answer: b Difficulty: MediumReference: p. 281
Primary Rate ISDN:
a. parcels information into 8-byte cells.
b. requires a fiber-optic line.
c. operates over cable TV lines as well as telephone lines.
d. is used for high-capacity Internet connections.
e. offers transmission capacities in the megabit range.
Answer: e Difficulty: HardReference: p. 281
Broadband:
a. works only for cable TV connections.
b. designates a communications medium that can transmit multiple channels of data simultaneously.
c. enables voice and data to run on a single network.
d. is for high-frequency transmissions.
e. does not maintain separate networks for voice and data.
Answer: b Difficulty: EasyReference: p. 281
A voice mail system:
a. is necessary for groupware to work efficiently.
b. allows data conferencing.
c. digitizes the sender’s spoken message, transmits it over a network, and stores it for later retrieval.
d. allows simultaneous conference via telephone.
e. All of the above.
Answer: c Difficulty: EasyReference: p. 283
Electronic conferencing is growing in popularity because:
a. travel time and costs are saved.
b. special software is not required.
c. any T1 line can use it.
d. employees can be monitored more closely.
e. of all of the above.
Answer: a Difficulty: EasyReference: p. 284
“E-learning” is the term used to describe:
a. training in network technologies.
b. surfing the Internet.
c. training delivered over a distance.
d. on-line instruction delivered over the Internet or private networks.
e. what companies are finding out about new technologies.
Answer: d Difficulty: MediumReference: p. 285
Fill In the Blanks
A(n) telecommunications system is a collection of compatible hardware and software arranged to communicate information from one location to another.
Difficulty: EasyReference: p. 266
A(n) router is a specialized communications processor that forwards data packets from one network to another network.
Difficulty: MediumReference: p. 268
Packet switching is technology that breaks messages into small, fixed bundles of data and routes them in the most economical way through any available communications channel.
Difficulty: EasyReference: p. 268
A(n) protocol is a set of rules and procedures that govern transmission between the components in a network.
Difficulty: MediumReference: p. 269
A(n) analog signal is a continuous waveform that passes through a communications medium.
Difficulty: MediumReference: p. 270
A(n) digital signal is a discrete waveform that transmits data coded into two discrete states as 1-bits and 0-bits, which are represented as on-off electrical pulses.
Difficulty: EasyReference: p. 270
A(n) modem is a device for translating a computer’s digital signals into analog form for transmission over ordinary telephone lines, or for translating analog signals back into digital form for reception by a computer.
Difficulty: EasyReference: p. 270
A(n) channel is the link by which data or voice is transmitted between sending and receiving devices in a network.
Difficulty: MediumReference: p. 270
A(n) twisted wire is a transmission medium consisting of pairs of copper wires.
Difficulty: EasyReference: p. 270
A(n) coaxial cable is a transmission medium consisting of thickly insulated copper wire that can transmit large volumes of data quickly.
Difficulty: EasyReference: p. 271
A(n) fiber-optic cable is a fast, light, and durable transmission medium consisting of thin strands of clear glass fiber bound into cables.
Difficulty: EasyReference: p. 271
A(n) backbone is the part of a network that handles the major traffic and provides the primary path for traffic flowing to or from other networks.
Difficulty: MediumReference: p. 271
A(n) optical network is high-speed networking technology for transmitting data in the form of light pulses.
Difficulty: MediumReference: p. 271
Dense wave division multiplexing is a technology for boosting transmission capacity of optical fiber by using many different wavelengths to carry separate streams of data over the same fiber strand at the same time.
Difficulty: HardReference: p. 271
Microwaveis a high-volume, long-distance point-to-point transmission in which high-frequency radio signals are transmitted through the atmosphere from one terrestrial transmission station to another.
Difficulty: MediumReference: p. 272
Satellite transmission of data uses orbiting satellites that serve as relay stations for transmitting microwave signals over very long distances.
Difficulty: EasyReference: p. 272
A(n) paging system is a wireless transmission technology in which the receiver beeps when the user receives a message; it is used to transmit short alphanumeric messages.
Difficulty: EasyReference: p. 273
A(n) cellular telephone is a device that transmits voice or data using radio waves to communicate with radio antennas placed within adjacent geographic areas.
Difficulty: EasyReference: p. 273
Personal communication services use a wireless cellular technology that uses lower power, higher-frequency radio waves than does cellular technology.
Difficulty: MediumReference: p. 273
A(n) personal digital assistant is a small, pen-based, hand-held computer with built-in wireless telecommunications capable of entirely digital communications transmission.
Difficulty: MediumReference: p. 273
A(n) smart phone is a wireless phone with voice, text, and Internet capabilities.
Difficulty: EasyReference: p. 274
A(n) mobile data network is a wireless network that enables two-way transmission of data files cheaply and efficiently.
Difficulty: MediumReference: p. 274
Baud is a change in signal from positive to negative or vice versa that is used as a measure of transmission speed.
Difficulty: MediumReference: p. 274
Bandwidth is the capacity of a communications channel as measured by the difference between the highest and lowest frequencies that can be transmitted by that channel.
Difficulty: MediumReference: p. 274
A(n) local area network requires its own dedicated channels and encompasses a limited distance, usually one building or several buildings in proximity.
Difficulty: MediumReference: p. 275
Topology is the way in which the components of a network are connected.
Difficulty: EasyReference: p. 276
A(n) bus network has a number of computers linked by a single circuit with all messages broadcast to the entire network.
Difficulty: MediumReference: p. 276
A(n) ring network has a number of computers linked by a closed loop in a manner that passes data in one direction from one computer to another.
Difficulty: MediumReference: p. 276
A(n) network operating system is special software that routes and manages communications on the network and coordinates network resources.
Difficulty: EasyReference: p. 276
A(n) peer-to-peer network architecture gives equal power to all computers on the network.
Difficulty: EasyReference: p. 276
A(n) wide area network is a network that spans a large geographical distance.
Difficulty: EasyReference: p. 279
A(n) dedicated line is a phone line that is continuously available for transmission by a lessee.
Difficulty: EasyReference: p. 279
A(n) value-added network is a private, multipath, data-only, third-party-managed network that multiple organizations use on a subscription basis.
Difficulty: MediumReference: p. 279
A(n) frame relay is a shared network service technology that packages data into bundles for transmission but does not use extensive error-correction routines.
Difficulty: MediumReference: p. 281
Asynchronous transfer mode is a networking technology that parcels information into 8-byte cells, allowing data to be transmitted between computers from different vendors at high speeds.
Difficulty: MediumReference: p. 281
Integrated Services Digital Network is an international standard for transmitting voice, video, image, and data to support a wide range of service over the public telephone lines.
Difficulty: HardReference: p. 281
Digital subscriber line refers to a group of technologies providing high-capacity transmission over existing copper telephone lines.
Difficulty: MediumReference: p. 281
A(n) T1 line is a dedicated telephone connection comprising 24 channels that can support a data transmission rate of 1.544 megabits per second.
Difficulty: EasyReference: p. 281
Broadband is a high-speed transmission technology; it also designates a single communications medium that can transmit multiple channels of data simultaneously.
Difficulty: MediumReference: p. 281
A(n) converged network is a network with technology to enable voice, video, and data to run over a single network.
Difficulty: MediumReference: p. 281
Essay Questions
Briefly describe the three major developments that have shaped contemporary digital telecommunications systems. The textbook mentions client/server computing, packet switching, and TCP/IP as the three major developments. Client/server computing is a model of computing that divides the processing between client computers and servers on a network. The tasks are assigned to the machine most able to perform the tasks. Packet switching breaks messages into small, fixed bundles of data and routes them in the most economical way through any available communications channel. Packet switching enables packets to be transmitted independently through various communications channels. TCP/IP is the connectivity model of the Internet, providing a universally agreed-on method for breaking up digital messages into packets, routing them to the proper addresses, and then reassembling them into coherent messages.
List and describe the three major LAN topologies. What are the advantages and disadvantages of each? Star, bus, and ring are the three major LAN topologies. The star topology consists of a central host computer connected to a number of smaller computers or terminals. It is useful for applications where some processing must be centralized and some can be performed locally. All communications between points in the network must pass through the central computer. One problem with this topology is that everyone in the network goes down if the central computer fails for any reason. The bus topology links a number of computers by a single circuit made of twisted wire, coaxial cable, or fiber-optic cable. All signals are broadcast in both directions to the entire network, with special software to identify which components receive each message. There is no central computer controlling the network. If one of the computers fails, none of the others are affected, and work can continue. However, since the channel can handle only one message at a time, performance can degrade if there is a high volume of network traffic. The ring topology like the bus network does not rely on a central host and will not necessarily break down if one of the component computers malfunctions. Each computer in the network can communicate directly with any other computer, and each processes its own applications independently. However, in a ring topology, the connecting wire forms a closed loop, and all data flows in one direction around the loop.
What is TCP/IP? Identify its layers. TCP/IP is the connectivity model used by the Internet; it provides a universally agreed-on method for breaking up digital messages into packets, routing them to the proper addresses, and then reassembling them into coherent messages. The TCP/IP layers are application, transport, internet, and network interface.
Distinguish between an analog signal and a digital signal. An analog signal is a continuous waveform passing through a communications medium. Analog signals handle voice communications and reflect variations in pitch. A digital signal is a discrete, rather than a continuous waveform, using only two states, 1-bits and 0-bits representing either/or conditions or on-off electrical pulses.
Standard telephone lines speak analog; computers speak digital. To communicate, the digital signal either 1) must be changed to an analog signal as it travels the medium, then changed back to a digital signal for the computer at the other end, or 2) sent in digital pulses over a medium that is also digital.
List and describe the three forms of wired transmission used in the telecommunications industry, and give one advantage and one disadvantage for each. Twisted wire refers to strands of copper wire twisted in pairs. Most standard telephone lines are twisted pairs and have been for many years. Twisted pairs can be used for digital transmission as well as analog. Its main advantages are low cost and it is already in place. Disadvantages include relatively slow for transmitting data, and the problem of “crosstalk” in which the signal “bleeds” from one wire to another during high-speed transmission. Coaxial cable is thickly insulated copper wire, which can transmit a larger volume of data than twisted wire. Advantages include its speed and having less interference. Disadvantages include the cable is thick and heavy, and it is hard to install in many buildings. Also, it cannot support analog phone conversations. Fiber-optic cable consists of thousands of very thin strands of clear glass fiber, bound into a cable. Data are transmitted over each strand by pulses of light, which are sent by laser at very high speed. Fiber optic advantages include faster, lighter, more durable, and the ability to transfer large volumes of data quickly. Its disadvantages are that it is difficult to work with, expensive, and harder to install.
Define “wireless transmission” and list at least two advantages and two disadvantages to its use. Wireless transmission sends signals (using the electromagnetic spectrum) through air or space without any physical tether. Common technologies for wireless transmission include microwave transmission, communication satellites, pagers, cell phones, personal communication services, smart phones, personal digital assistants, and mobile data networks. Advantages include no limitation on where communications may take place, since the signal can be bounced off satellites to line-of-sight towers and no limitation of the movement of the persons communicating, because no wires are involved. Disadvantages include being more expensive, slower, and more error prone than wired networks. Security and privacy are difficult because wireless transmissions are easily intercepted. Different wireless networks cannot transmit data seamlessly if they use incompatible standards or different frequencies.
Briefly discuss Wi-Fi. Wi-Fi is the emerging standard for wireless LANs. The 802.a standard transmits up to 54 Mbps in the unlicensed 5-Ghz frequency range and has an effective distance up to 30 meters. The 802.11b standard transmits up to 11 Mbps in the unlicensed 2.4 GHz band and has an effective distance up to 50 meters. The 802.11g standard transmits up to 54 Mbps in the 2.4 GHz range. Wi-Fi systems can operate either in infrastructure or ad-hoc mode. When operating in infrastructure mode, wireless devices communicate with a LAN through access points. In ad-hoc mode, wireless devices communicate directly and do not use access points.
What are at least five considerations management must examine to establish the telecommunications needs of a company? Management should consider the following:
1. Distance—are the needs of the company local or long-distance?
2. Services—what range of services will be needed (e-mail, EDI, voice mail, videoconferencing, graphics transmission)? Do they need to be integrated?
3. Points of access—how many different locations and users in the organization require access to the communications services and capabilities?
4. Utilization—what frequency and volume of communications does your firm anticipate?
5. Cost—how much can you spend and on what?
6. Security—what level of security and reliability must be maintained?
7. Connectivity—how much time, money, and effort will be required to make sure all the components of the network or multiple networks can communicate with each other?
Distinguish between EDI and ATM. ATM is “asynchronous transfer mode” and is capable of seamlessly switching voice, data, images, and video between users using computers from different vendors. EDI is the computer-to-computer exchange between two organizations of standard transaction documents such as invoices, bills of lading, and purchase orders.
Distinguish between the two types of ISDN services and the two types of DSL services. ISDN—stands for Integrated Services Digital Network, and is an international standard for dial-up network access that integrates voice, data, image, and video services in a single link. Basic rate ISDN can transmit data at a rate of 128 kilobits per second on an existing local telephone line. Primary rate ISDN offers transmission capacities in the megabit range and is designed for large users of telecommunications services.
DSL—stands for Digital Subscriber Line, and also carry e-mail, data, image, and video services in a single link over regular copper phone lines, but they have higher transmission capacities than ISDN. ADSL (asymmetric digital subscriber line) supports 1.5 to 9 megabits per second when receiving data and up to 640 kilobits per second when sending data. SDSL (symmetric digital subscriber line) supports the same transmission rate and can receive data at up to 3 megabits per second.
