Wireless Communications- Chapters 1-3 Test Study Guide
Kilohertz (KHz)
1,000 Hertz.
Megahertz (MHz)
1,000,000 Hertz.
Gigahertz (GHz)
1,000,000,000 Hertz.
Mixer
A component that combines two inputs to create a single output.
Dibit
A signal unit that represents 2 bits.
Explain how implementing a wireless network can be helpful in case of disaster recovery.
In the event of a disaster such as a flood or fire, managers can quickly relocate the office without needing to find a new facility with network wiring.
Electromagnetic interference (EMI)
Interference with a radio signal; also called noise.
Changing a signal to encode data onto it is known as __________.
Modulation
Switching
Moving a signal from one wire or frequency to another.
______ is a method of transmission in which the information is broken up into smaller units.
Packet switching
Bluetooth devices communicate using small radio transceivers called ___________ that are built onto microprocessor chips.
Radio modules
ROYGBIV
Red, Orange, Yellow, Green, Blue, Indigo, Violet
Hertz (Hz)
The number of cycles per second.
Without switching, 1,225 cables would be required to interconnect 50 telephones.
True
Eight binary digits grouped together form which of the following?
byte
Wi-Fi
A certification label awarded to IEEE 802.11 WLAN-compatible wireless devices that pass all interoperability tests performed by an organization called the Wi-Fi Alliance. The acronym is often thought to stand for Wireless Fidelity, but this is a common misconception. The name was chosen by the alliance purely for marketing reasons and is not an acronym at all.
Baud
A change in a carrier signal.
Amplifier
A component that increases a signal's intensity.
Emitter
A laser diode or a light-emitting diode that transmits a light-based signal.
Diffused transmission
A light-based transmission that relies on reflected light.
Directed transmission
A light-based transmission that requires the emitter and detector to be directly aimed at one another.
Wireless local area network (WLAN)
A local area network that is not connected by wires but instead uses wireless technology. Its range extends to approximately 100 meters and has a maximum data rate of 600 Mbps. Today's WLANs are based on IEEE 802.11a/b/g/n standards.
Attenuation
A loss of signal strength.
Analog modulation
A method of encoding an analog signal onto a carrier wave.
Tribit
A signal unit that represents 3 bits.
Quadbit
A signal unit that represents 4 bits.
Binary phase shift keying (BPSK)
A simple digital modulation technique that uses four phase changes to represent 2 bits per signal change.
Piconet
A small network composed of two or more Bluetooth devices that are exchanging data with each other.
Radio frequency identification (RFID)
A small tag placed on product packaging and boxes that can be remotely activated and read by remote sensors. The data about the product is then transferred directly to an information-processing system for inventory control, location tracking, and item counting.
Packet
A smaller segment of the transmitted signal.
WirelessHD
A specification for the wireless transmission of high-definition video (HD), multichannel audio and data between consumer devices such as televisions, stereo systems, and Blu-ray players, using the 60 GHz frequency band.
Frequency hopping spread spectrum (FHSS)
A spread spectrum technique that uses a range of frequencies and changes frequencies during the transmission.
Circuit switching
A switching technique in which a dedicated and direct physical connection is made between two transmitting devices—for example, between two telephones during a call.
Microbrowser
A tiny browser program that runs on a WAP or WAP2 cellular phone.
J2ME (Java 2 Micro Edition)
A variation of the Java programming language designed for use in portable devices such as PDAs and cellular phones.
Wireless personal area network (WPAN)
A very small network that typically extends to 10 meters or less. Due to its limited range, WPAN technology is used mainly as a replacement for cables. See also piconet and Ultra Wide Band.
Ultra Wide Band (UWB)
A wireless communications technology that allows devices to transmit data at hundreds of megabits or even gigabits per second at short distances—up to 6 feet (2 meters) at the higher speeds and up to 150 feet (50 meters) at lower speeds.
light spectrum
All the different types of light that travel from the Sun to the Earth.
WiGig
An alliance of companies involved in developing a common wireless specification for connecting computers, communication, and entertainment devices over short ranges, using the 60 GHz band at multi-gigabit speeds.
Unlike a digital signal, a(n) ________ signal is a continuous signal with no "breaks" in it.
Analog
Digital signal
Data that is discrete or separate.
Packet switching
Data transmission that is broken into smaller units.
Voltage
Electrical pressure.
Infrared wireless systems require that each device have only one component: either an emitter that transmits a signal or a detector that receives the signal.
False, Infrared wireless systems require that each device have two components: an emitter that transmits a signal and a detector that receives the signal.
Noise
Interference with a signal.
Crosstalk
Signals from close frequencies that may interfere with other signals.
"WAP2" stands for ________________.
Wireless Application Protocol version 2
Describe how wireless networks can reduce installation time.
Wireless networks eliminate the need to install cables, which is a slow and expensive process.
Radio frequency spectrum
The entire range of all radio frequencies that exist.
Bits per second (bps)
The number of bits that can be transmitted per second.
Digital convergence
The power of digital devices such as desktop computers and wireless handhelds to combine voice, video, and text-processing capabilities as well as to be connected to business and home networks and to the Internet.
Federal Communications Commission (FCC)
The primary U.S. regulatory agency for telecommunications.
Hypertext Markup Language (HTML)
The standard language for displaying Web pages.
Sidebands
The sum and the differences of the frequency carrier that serve as buffer space around the frequency of the transmitted signal.
Half-duplex transmission
Transmissions that occur in both directions but only one way at a time.
Simplex transmission
Transmissions that occur in only one direction.
Narrow-band transmissions
Transmissions that use one radio frequency or a very narrow portion of the frequency spectrum.
License exempt spectrum
Unregulated radio frequency bands that are available in the United States to any users without a license.
Motes
Remote sensors used for collecting data from manufacturing equipment or for scientific research, which can communicate using wireless technology.
Official standards
See de jure standards.
Unregulated bands
See license exempt spectrum.
Non-return-to-zero level (NRZ-L)
See polar non-return-to-zero.
The new fourth generation (4G) cellular technology will allow data to be transmitted at a maximum speed of __________ Mbps.
150 Mbps
IEEE 802.11n devices can be as far as 375 feet apart and can send and receive data at up to ________ million bits per second (Mbps).
600
Wireless wide area network (WWAN)
A WAN that uses cellular phone technologies and encompasses any geographical region, including the entire globe.
Explain how a WAP cellular phone sends and receives Internet data.
A WAP-enabled cellular phone sends and receives internet data in the form of a deck of cards. Data transmitted to this type of cellular phone must first be translated by a WAP server from a Web site. Data transmitted from a WAP-enabled cellular phone to the Internet is sent via the WAP server before it is forwarded to an Internet server.
Non-return-to-zero, invert-on-ones (NRZ-I)
A binary signaling technique that changes the voltage level only when the bit to be represented is a 1.
Polar non-return-to-zero (polar NRZ)
A binary signaling technique that increases the voltage to represent a 1 bit but drops to negative voltage to represent a 0 bit.
Non-return-to-zero (NRZ)
A binary signaling technique that increases the voltage to represent a 1 bit but provides no voltage for a 0 bit.
Return-to-zero (RZ)
A binary signaling technique that increases the voltage to represent a 1 bit, but the voltage is reduced to 0 before the end of the period for transmitting the 1 bit, and there is no voltage for a 0 bit.
Barker code (chipping code)
A bit pattern used in a DSSS transmission. The term chipping code is used because a single radio bit is commonly referred to as a chip.
American National Standards Institute (ANSI)
A clearinghouse for standards development in the United States.
Pseudo-random code
A code that is usually derived through a number of mathematical calculations as well as practical experimentation.
Quadrature amplitude modulation (QAM)
A combination of phase modulation with amplitude modulation to produce 16 different signals.
Filter
A component that is used to either accept or block a radio frequency signal.
Antenna
A copper wire, rod, or similar device that has one end up in the air and the other end connected to the ground through a receiver.
Repeater
A device commonly used in satellite communications that simply "repeats" the signal to another location.
Smartphone
A device that combines a cellular phone with the capabilities of a personal digital assistant (PDA). These devices provide the user with the ability to enter appointments in a calendar, write notes, send and receive e-mail, and browse Web sites, among other functions.
Wireless network interface card (wireless NIC)
A device that connects to a PC to transmit And receive network data over radio waves. It includes an antenna for wireless communication between networked devices.
Access point (AP or wireless AP)
A device that receives the signals and transmits signals back to wireless network interface cards (NICs).
Modem (MOdulator/DEModulator)
A device used to convert digital signals into an analog format, and vice versa.
3G (third generation)
A digital cellular technology that can send data at up to 21 Mbps over the cellular telephone network.
4G (fourth generation)
A digital cellular technology that can transmit and receive data at theoretical speeds up to 20 Mbps when users are moving fast and up to 150 Mbps (theoretically) when users are moving slowly or are stationary.
Frequency shift keying (FSK)
A digital modulation technique that changes the frequency of the carrier signal in response to a change in the binary input signal.
Phase shift keying (PSK)
A digital modulation technique that changes the starting point of a wave cycle in response to a change in the binary input signal.
Quadrature phase shift keying (QPSK)
A digital modulation technique that combines quadrature amplitude modulation with phase shift keying.
amplitude shift keying (ASK)
A digital modulation technique whereby a 1 bit is represented by the existence of a carrier signal, whereas a 0 bit is represented by the absence of a carrier signal.
Detector
A diode that receives a light-based transmission signal.
High-pass filter
A filter that passes all signals that are above a maximum threshold.
Low-pass filter
A filter that passes all signals that are below a maximum threshold.
Bandpass filter
A filter that passes all signals that are between the maximum and minimum threshold.
Optical fiber
A glass strand, about the thickness of a human hair, that carriers data signals encoded in a laser beam.
Constellation diagram
A graphical representation that makes it easier to visualize signals using complex modulation techniques such as QAM. It is generally used in laboratory and field diagnostic instruments and analyzers to aid in design and troubleshooting of wireless communications devices.
Telecommunications Industries Association (TIA)
A group of more than 600 companies that manufacture or supply the products and services used in global communications.
Personal digital assistant (PDA)
A handheld computer device used for taking notes, making appointments, creating to-do lists, and communicating with other devices.
Frequency
A measurement of radio waves that is determined by how frequently a cycle occurs.
Digital modulation
A method of encoding a digital signal onto an analog carrier wave for transmission over media that does not support direct digital signal transmission.
Passband
A minimum and maximum threshold that spells out which range of frequencies will pass through a filter.
Satellite radio
A pay-for-service radio broadcast system that transmits digital programming directly from satellites to a network of ground-based repeaters and that holds the signal regardless of the listener's location. Users must purchase special receivers and pay a monthly subscription fee to listen to commercial-free music channels. Because the digital transmission is decoded at the receivers, the sound quality is also much better than conventional FM radio.
Internet Society (ISOC)
A professional-membership organization of Internet experts that comments on policies and practices and oversees a number of other boards and task forces dealing with network policy issues.
Frequency Division Multiple Access (FDMA)
A radio transmission technique that divides the bandwidth of the frequency into several smaller frequency bands.
Adaptive array processing
A radio transmission technique that replaces a traditional antenna with an array of antenna elements.
Institute of Electrical and Electronic Engineers (IEEE) 802.11n-2009
A set of standards that allows WLAN computers to transmit data at speeds ranging from 1 Mbps to a maximum of 600 Mbps. 802.11n (or 802.11n-2009, as the specification is now called) can also make use of the 5 GHz band in addition to the 24 GHz band.
Institute of Electrical and Electronic Engineers (IEEE) 802.16 Fixed Broadband Wireless
A set of standards, some established and some still under development, for fixed and mobile broadband wireless communications that allows computers to communicate at up to 75 Mbps and at distances of up to 35 miles (56 km) in a point-to-point configuration. This set of standards also allows the use of both licensed and unlicensed frequencies.
Electromagnetic wave (EM wave)
A signal composed of electrical and magnetic forces that in radio transmission usually propagates from an antenna and can be modulated to carry information.
Analog signal
A signal in which the intensity (amplitude or voltage) varies continuously and smoothly over a period of time.
Carrier signal
A signal of a particular frequency that is modulated to contain either analog or digital data.
Direct sequence spread spectrum (DSSS)
A spread spectrum technique that uses an expanded, redundant code to transmit each data bit.
Wireless Application Protocol (WAP or WAP2)
A standard for transmitting, formatting, and displaying Internet data on cellular phones. WAP can display only text. WAP2 supports HTML and can display color and pictures.
European Telecommunications Standards Institute (ETSI)
A standards body that develops telecommunications standards for use throughout Europe.
Institute of Electrical and Electronics Engineers (IEEE)
A standards body that establishes standards for telecommunications.
Internet Engineering Task Force (IETF)
A standards body that focuses on the lower levels of telecommunications technologies.
Amplitude modulation (AM)
A technique that changes the height of a carrier wave in response to a change in the height of the input signal.
Frequency modulation (FM)
A technique that changes the number of wave cycles in response to a change in the amplitude of the input signal.
Phase modulation (PM)
A technique that changes the starting point of a wave cycle in response to a change in the amplitude of the input signal. This technique is not used in analog modulation.
Spread spectrum transmission
A technique that takes a narrow signal and spreads it over a broader portion of the radio frequency band.
Code Division Multiple Access (CDMA)
A technique that uses spread spectrum technology and unique digital codes to send and receive radio transmissions.
Voice over Internet Protocol (VoIP)
A technology that allows voice telephone calls to be carried over the same network used to carry computer data.
Integrated Services Digital Networks (ISDN)
A technology that transmits data over telephone lines at a maximum of 256 Kbps.
Digital subscriber line (DSL)
A technology used to transmit data over a telephone line.
Cable modem
A technology used to transmit data over a television cable connection.
T1
A technology used to transmit data over special telephone lines at 1.544 Mbps.
Time Division Multiple Access (TDMA)
A transmission technique that divides the bandwidth into several time slots.
Oscillating signal
A wave that illustrates the change in a carrier signal.
Sine wave
A wave that illustrates the change in a carrier signal.
List and describe the three types of data flow.
Simplex is one-way transmission. Half-duplex is two-way transmission, but not at the same time. Full-duplex is simultaneous, two-way transmission.
Radio modules
Small radio transceivers built onto microprocessor chips and embedded into Bluetooth devices, which enable them to communicate.
Wireless metropolitan area network (WMAN)
A wireless network that covers a large geographical area such as a city or suburb. The technology is usually based on the IEEE 802.16 set of standards and can span an entire city, covering distances of up to 35 miles (56 km) between transmitters and receivers or repeaters.
Bluetooth
A wireless standard that enables devices to transmit data at up to 721.2 Kbps over a typical maximum distance of 33 feet. Bluetooth can transmit data farther, but devices that can use this capability are rare.
Explain the difference between amplitude modulation, frequency modulation, and phase modulation.
Amplitude modulation changes the height of a wave. Frequency modulation changes the frequency of a wave, and phase modulation changes the starting point of a wave with reference to the previous cycle of the same wave.
Explain how a WLAN can be used in a classroom.
An Instructor can create a classroom presentation on a notebook computer in his home or school office, then carry the computer right into the classroom. He does not have to plug and unplug cables to attach to the campus network. Instead, the notebook automatically connects to the classroom network as soon as the instructor walks into the room; it can even connect to multimedia display projectors without using wires.
An 802.11 wireless NIC, when configured to communicate with a wired network, sends its signals through invisible radio waves to ____________.
An access point
Explain the role of an access point (AP) in a WLAN.
An access point acts as a base station for all communications in a WLAN as well as an interface between the WLAN and the wired LAN.
International Telecommunication Union (ITU)
An agency of the United Nations that sets international telecommunications standards and coordinates global telecommunications networks and services.
Continuous wave (CW)
An analog or sine wave that is modulated to eventually carry information, becoming a carrier wave.
Directional antenna
An antenna that radiates the electromagnetic waves in one direction only. As a result, it can help reduce or eliminate the effect of multipath distortion if there is a clear line of sight between the two antennas.
American Standard Code for Information Interchange (ASCII)
An arbitrary coding scheme that uses the numbers from 0 to 127 to represent alphanumeric characters and symbols.
Radio wave (radiotelephony)
An electromagnetic wave created when an electric current passes through a wire and creates a magnetic field in the space around the wire.
ZigBee Alliance
An organization that creates protocols and specifications for devices used to wirelessly control lighting, as well as security and energy systems, for home and industry.
International Organization for Standardization (ISO)
An organization to promote international cooperation and standards in the areas of science, technology, and economics.
Cycle
An oscillating sine wave that completes one full series of movements.
Unlicensed National Information Infrastructure (U-NII)
An unregulated band approved by the FCC in 1996 to provide for short-range, high-speed wireless digital communications.
Industrial, Scientific and Medical (ISM) band
An unregulated radio frequency band approved by the FCC in 1985.
Which type of transmission is used when human voice is modulated directly onto a carrier wave?
Analog
Explain the difference between bps and baud rate.
Baud rate refers to the number of signal changes per second. Because each signal change can represent more than one bit, the number of bits-per-second, or bps, can be higher than the baud rate.
A _______ transmission uses spread spectrum technology and unique spreading codes for each user.
CDMA
De facto standards
Common practices that the industry follows for various reasons.
When signals are sent at frequencies that are closely grouped together, an errant signal may encroach on a close frequency, causing _______.
Crosstalk
PSK is an example of _______.
Digital Modulation
________ divides the bandwidth of the frequency into several narrower frequencies. Each user then transmits using its own narrower frequency channel.
FDMA
The American Standard Code for Information Interchange (ASCII) can represent up to 1024 characters.
False, ASCII can represent up to 128 different characters.
TDMA can carry three times the amount of data that CDMA can.
False, CDMA can carry three times the amount of data that TDMA can.
Eliminating installation costs is a disadvantage of a WLAN.
False, Eliminating installation costs is a advantage
When using the same antenna for full-duplex communications, the same frequency can be used for transmitting and receiving simultaneously.
False, most communications equipment the work in full-duplex mode send and receive on different frequencies.
The resulting output from the modulation process is known as the middle frequency (MF) signal.
False, the resulting output from the modulation process is known as the intermediate frequency (IF) signal.
Link manager
Special software in Bluetooth devices that helps identify other Bluetooth devices, creates the links between them, and sends and receives data.
De jure standards
Standards that are controlled by an organization or body.
List and describe the three different types of binary signaling techniques.
In return-to-zero, the absence of a voltage, or zero volts, represents a 0 bit and an increase in voltage represents a 1 bit. The signal rises and falls within a bit time period. In non-return-to-zero, the voltage does not change when the next bit is the same as the previous bit. Non-return to zero level, works the same way as non-return- to-zero, but the voltage changes between a positive and negative level, rather than between a positive voltage and zero volts, as in the previous two techniques.
What is switching? What type of switching is used with telephone transmissions, and what type is used for data transmissions?
In telephone systems, switching is moving a signal from a cable that connects to a residence or business to another cable so that two telephone sets are connected to each other. Circuit switching is used with telephone systems. Packet switching is breaking a message into small chunks and allowing multiple users to share the medium by sending a chunk from each user at a time.
Consortia
Industry-sponsored organizations that have the goal of promoting a specific technology.
Which range of the electromagnetic spectrum is less susceptible to interference from sources of visible light?
Infrared
List and discuss the advantages of standards.
Interoperability between equipment from different manufacturers; lower cost for manufacturers due to economies of scale; lower cost for users, eventually.
Harmonics
Stray oscillations that result from the process of modulating a wave and that fall outside the range of frequencies used for transmission. Harmonics also occur when a signal goes through a mixer and must be filtered out at several points before the signal is finally fed to the antenna for transmission.
Infrared light
Light that is next to visible light on the light spectrum and that has many of the same characteristics as visible light.
Each Bluetooth device uses a ____________, which is special software that helps identify other Bluetooth devices.
Link manager
Each of the following is a type of RF filter _____.
Low-pass, High-pass, & Bandpass
Ultra-wideband transmission (UWB)
Low-power, precisely timed pulses of energy that operate in the same frequency spectrum as low-end noise, such as that emitted by computer chips and TV monitors.
The automatic connection between various Bluetooth devices creates a network called a(n) ___________.
Piconet
PN code
Pseudo random code; a code that appears to be a random sequence of 1s and 0s but actually repeats itself. Used in CDMA cellular telephone technology.
What is quadrature amplitude modulation (QAM) and how does it work?
QAM is a modulation method that changes both the phase and height of a wave, in order to encode more than one bit per signal change (baud).
Which of the following divides the bandwidth of the frequency channel into several time slots?
TDMA
What does the Federal Communications Commission do regarding the licensing of radion frequencies?
The FCC regulates and monitors the use of the licensed portion of the frequency spectrum. This means that most of the available RF is licensed to certain users in a particular area and that no one else is allowed to use the same frequency in the same area of signal coverage.
Line of sight
The direct alignment as required in a directed transmission.
Amplitude
The height of a carrier wave.
Wavelength
The length of a wave as measured between two positive or negative peaks or between the starting point of one wave and the starting point of the next wave.
Signal-to-noise ratio (SNR)
The measure of signal strength relative to the background noise.
Baud rate
The number of times that a carrier signal changes per second.
Internet Architecture Board (IAB)
The organization responsible for defining the overall architecture of the Internet, providing guidance and broad direction to the IETF. The IAB also serves as the technology advisory group to the Internet Society and oversees a number of critical activities in support of the Internet.
Intermediate frequency (IF)
The output signal that results from the modulation process.
Modulation
The process of changing a carrier signal.
Bandwidth
The range of frequencies that can be transmitted.
Phase
The relative starting point of a wave, in degrees, beginning at zero degrees.
Hopping code
The sequence of changing frequencies used in FHSS.
Wireless communications
The transmission of user data between devices without the use of wires.
Why do computers and data transmission equipment use binary?
They are electrical devices, and electricity has only two states.
Full-duplex transmission
Transmissions in which data flows in either direction simultaneously.
A passband has both a minimum and maximum threshold.
True
A wireless network interface card performs basically the same functions and looks similar to a traditional network interface (NIC) card.
True
An earth station transmits to a satellite at one frequency, and the satellite regenerates and transmits the signal back to earth at another frequency.
True
Bluetooth can send data through physical barriers, like walls.
True
Infrared light, though invisible, has many of the characteristics of visible light.
True
Infrared wireless systems send data by the intensity of the light wave instead of whether the light signal is on or off.
True
Letters of the alphabet and symbols are stored using the ASCII code, but not numbers used in calculations.
True
Most Bluetooth devices can transmit data at up to 1 Mbps over a distance of 33 feet (10 meters).
True
When mixing two signals, the highest sum and the smallest difference between the carrier frequency and the range of frequencies at the other input define two limits known as the sidebands of the frequency carrier.
True
_________ provides a standard way to transmit, format, and display Internet data on cellular phones.
WAP2
The distance between one positive peak and the next positive peak of a wave is called: _________.
Wavelength
Explain multipath distortion and how it can be minimized.
Waves are reflected and arrive at the receiver at different times due to the fact that reflected waves have traveled farther before reaching the receiver. These waves can frequently arrive at the receiver antenna out of phase with the signal that reaches the antenna via a shorter, more direct path. Increasing signal strength and using directional antennas are two ways of minimizing multipath distortion.
Multipath distortion
What occurs when the same signal reflects and arrives at the receiver's antenna from several different directions and at different times.
Explain how a radio antenna works when transmitting a signal.
When the electricity moves back and forth in the antenna at the same frequency as the radio waves, it creates both a magnetic field and an electrical field around the antenna. This continuous (analog) combination of magnetism and electrical pressure moves away (propagates) from the antenna the same way that water waves move away from the point of impact when you throw a rock in a pond.
__________ uses wireless transmissions for data communications as much as 35 miles apart.
WiMAX
A(n) ______ actively increases a signal's intensity or strength.
amplifier
Radio frequency (RF)
communications All types of radio communications that use radio frequency waves.
Ultra Wide Band technology is used primarily for _____________________.
connecting devices inside the home at very high speeds
Infrared wireless transmission can be either directed or _________.
diffused
Radiotelephony or radio travels in waves known as _________ waves.
electromagnetic
The result of using a PN code is that ________.
it spreads the signal over a wider range of frequencies
A(n) ______ combines two inputs to create a single output.
mixer
