Wireless Communications Fundamentals

253 flashcards

Wireless communication
Transmission of digital data while connected to a data network without using wires.
Wi-Fi / WLAN
A wireless local area network that allows devices to connect to local network resources and the Internet without a physical network cable.
Voice over Internet Protocol (VoIP)
Technology that carries voice calls over Internet-based networks.
Wireless access point (AP)
A device that wireless clients connect through to join a WLAN.
Wireless network interface card (wireless NIC)
The network hardware in a wireless device that allows it to connect to an AP or wireless router.
IEEE
Institute of Electrical and Electronic Engineers, which publishes WLAN and other networking standards.
Bluetooth
Very short-range wireless technology designed mainly to eliminate cables between nearby devices.
Radio module
A small, low-power wireless transceiver used by Bluetooth and other wireless devices.
Link manager
Bluetooth software that identifies nearby devices, establishes links, and manages data exchange.
iBeacon
A Bluetooth-based transmitter technology for sending instructions or location-related information through smartphone apps.
Piconet / WPAN
A small wireless personal area network created when two or more Bluetooth devices exchange data.
ZigBee
A low-power wireless communication specification based on IEEE 802.15.4 and used in applications such as home and building automation.
Matter
A newer home and building connectivity specification intended to bring smart-home technologies into a common application framework.
Thread
A technology introduced to support Internet of Things devices.
WiGig
A very high-speed, very short-range wireless technology designed primarily for in-room use.
Ultra Wide Band (UWB)
Radio technology supporting WiGig high-speed, short-range transmission.
RFID
Radio frequency identification; a short-range technology that uses radio waves and electronic tags to identify or track items.
RFID tag
An electronic tag containing circuitry and an antenna that stores information that can be read wirelessly.
RFID reader / interrogator
A device that emits electromagnetic waves and retrieves information from RFID tags.
Active RFID tag
A battery-powered RFID tag that can operate over a longer range.
NFC
Near field communication; extremely short-range wireless communication, generally a few inches, used for interactions such as tap-to-pay.
Satellite network
A wireless network that uses satellites and Earth-based stations to communicate over long distances.
Repeater
A device that receives a signal and retransmits it, such as a satellite forwarding signals between Earth locations.
Global Positioning System (GPS)
A positioning technology based on satellites.
Cellular network
A mobile network that divides a geographic area into cells served by transmission towers.
Cell
A geographic coverage area in a cellular network that serves a limited number of users.
Wireless tethering / hotspot
Sharing a device's cellular Internet connection with nearby devices through Wi-Fi.
4G
Fourth-generation cellular data technology providing much higher data rates than earlier cellular generations.
WWAN
Wireless wide area network; a network that uses cellular or other mobile technologies to provide connectivity over a large area.
Internet of Things (IoT)
Connected devices and sensors that exchange data over networks.
LoRa
Long Range, a wireless technology used for some IoT applications.
Fixed broadband wireless
Wireless links used to provide broadband connectivity between fixed locations, especially where wired service is unavailable.
WMAN
Wireless metropolitan area network; a network designed to cover a metropolitan-scale area.
WiMAX
A fixed broadband wireless technology based on IEEE 802.16 and used as an example of WMAN connectivity.
Digital convergence
The combining of voice, video, text/data processing, networking, and Internet capabilities in digital devices and networks.
Mobility
The ability to move while remaining connected without being tethered by network cables.
AES
Advanced Encryption Standard, a widely used secure method of encryption.
Jamming attack
An attempt to disrupt wireless radio communication and prevent access to the network.
Rogue access point
An unauthorized wireless access point connected to a network that creates a security risk.
Radio frequency (RF)
Radio-frequency energy used by wireless devices to transmit signals.
Electromagnetic (EM) wave
A wave made of changing electric and magnetic fields that can travel through space and carry energy or information.
Infrared light
Electromagnetic energy just beyond visible red light that can be used for short-range wireless communication.
Emitter
A device, such as an LED or laser diode, that transmits an infrared signal.
Detector
A device that receives infrared light and converts it into an electrical signal.
Line-of-sight
A transmission path in which the transmitter and receiver must be directly aimed toward one another.
Diffused infrared
Infrared transmission that reaches a receiver by reflecting from surfaces rather than traveling only in a direct line.
Radio wave
An electromagnetic wave in the radio-frequency portion of the spectrum, widely used for wireless communication.
Analog signal
A signal that changes continuously over time.
Digital signal
A signal made of discrete states or pulses, commonly used to represent binary 1s and 0s.
Modulation
The process of changing a carrier signal so that it carries information.
Modem
A modulator/demodulator that converts information into a form suitable for transmission and back again.
Frequency
The number of complete wave cycles that occur each second.
Hertz (Hz)
The unit used to measure frequency; one hertz equals one cycle per second.
Wavelength
The distance from a point in one wave cycle to the same point in the next cycle.
Amplitude
The height or strength of a wave relative to its reference level.
Phase
The position of a wave within its 360-degree cycle.
Carrier wave
A continuous radio wave whose properties are changed through modulation to carry information.
Bits per second (bps)
A measure of how many bits are transmitted each second.
Bandwidth
The range of frequencies occupied or available for a transmission.
Amplitude Modulation (AM)
Analog modulation that changes the carrier wave's amplitude.
Frequency Modulation (FM)
Analog modulation that changes the carrier wave's frequency.
Phase Modulation (PM)
Analog modulation that shifts the starting position or phase of the carrier wave.
ASK
A digital modulation technique that represents values by changing carrier amplitude.
FSK
A digital modulation technique that represents values using different carrier frequencies.
PSK
A digital modulation technique that represents values by shifting carrier phase.
QAM
A digital modulation technique that combines amplitude and phase changes to represent multiple bits per symbol.
Spread spectrum
A transmission approach that distributes a signal across a wider frequency range to improve resistance to interference.
FHSS
Frequency Hopping Spread Spectrum; a method that changes among frequencies according to a shared hopping sequence.
Hopping code
The agreed sequence of frequencies used by an FHSS transmitter and receiver.
DSSS
Direct Sequence Spread Spectrum; a method that expands data with a longer chip sequence before transmission.
Chipping code
A known sequence used by DSSS to spread and later recover the transmitted data.
OFDM
Orthogonal Frequency Division Multiplexing; a technique that divides a channel into many parallel subcarriers.
Filter
A circuit or device that passes wanted frequencies and rejects unwanted frequencies.
Mixer
A radio component that combines frequency inputs to create new output frequencies.
Amplifier
An active device that uses electrical power to increase the strength or amplitude of a signal.
FDMA
Frequency Division Multiple Access; divides available bandwidth into separate frequency bands for different users.
TDMA
Time Division Multiple Access; lets users take turns using a frequency during assigned repeating time slots.
CDMA
Code Division Multiple Access; lets users share frequency resources by using different spreading codes.
Signal-to-noise ratio (SNR)
A comparison of the desired signal strength to the background noise level.
Gain
An increase in signal power resulting from amplification or directional concentration.
Decibel (dB)
A ratio used to express the change or relative difference between two signal levels.
Isotropic radiator
A theoretical reference antenna that radiates RF energy equally in all directions.
Omnidirectional antenna
An antenna designed to transmit and receive signals in all horizontal directions.
Fresnel zone
The elliptical region around the direct RF path that should be kept at least 60 percent clear of obstructions.
Link budget
A calculation of gains and losses used to determine if the receiver gets enough usable signal strength.
Antenna polarization
The orientation of the RF wave as it leaves the antenna, such as vertical or horizontal.
Passive antenna
An antenna constructed of conductive material that does not electronically amplify the signal.
Active antenna
A passive antenna with a built-in amplifier connected directly to the radiating element.
Yagi antenna
A directional antenna with a wider, less focused RF beam than a dish.
Parabolic dish antenna
A highly directional antenna that concentrates RF energy into a narrow beam.
Patch antenna
A semi-directional antenna with a horizontally narrow and vertically taller beam often used in corridors.
Azimuth pattern
A radiation pattern showing the shape of the signal emitted when viewed from above.
Elevation pattern
A radiation pattern showing the shape of the signal emitted when viewed from the side.
Low-pass filter
A filter that passes frequencies below a selected maximum or cutoff frequency.
High-pass filter
A filter that passes frequencies above a selected minimum or cutoff frequency.
Bandpass filter
A filter that passes frequencies within a selected range called a passband.
Guard band
Unused frequency space placed between signals to reduce interference.
Simplex
Communication that travels in only one direction.
Half-duplex
Two-way communication in which only one side transmits at a time.
Full-duplex
Two-way communication in which both sides can transmit at the same time.
Circuit switching
A switching method that establishes a dedicated path between endpoints.
Packet switching
A switching method that breaks data into packets that share network resources.
Adaptive array processing
The use of multiple antenna elements to direct stronger RF energy toward selected users or devices.
dBm
An absolute power level referenced to 1 milliwatt, where 0 dBm equals 1 mW.
dBi
Antenna gain compared with an ideal isotropic radiator.
dBd
Antenna gain compared with a dipole antenna.
Free-space loss
Loss in signal strength as RF energy spreads away from the transmitting antenna over distance.
Ground wave
A radio wave that follows the curvature of the Earth.
Sky wave
A radio wave that travels by reflecting between the ionosphere and Earth.
Switched-beam antenna
A smart antenna that selects among several narrow beams pointed in different directions.
De facto standard
An unofficial standard that becomes common practice in an industry.
De jure standard
An official standard controlled or approved by a recognized standards organization or body.
Consortium
An industry-sponsored group that promotes or develops a particular technology or standard.
FCC
Federal Communications Commission, the primary U.S. telecommunications regulatory agency.
ISM band
Industrial, Scientific and Medical band; a license-exempt band category used by various wireless technologies.
U-NII
Unlicensed National Information Infrastructure frequency bands used for WLAN and related applications.
Licensed spectrum
Frequency use that requires authorization or licensing under applicable regulatory rules.
License-exempt spectrum
Frequency bands that may be used without an individual spectrum license when technical rules are followed.
Passband
The frequency range that a bandpass filter is designed to allow through.
Harmonics
Unwanted frequency components that can be created during modulation and may need to be filtered.
Intermediate frequency (IF)
An intermediate signal frequency used inside a radio system during modulation or frequency conversion.
Sideband
A frequency component produced above or below a carrier as a result of modulation or mixing.
Crosstalk
Interference caused when a signal encroaches on a neighboring channel.
PN code
A pseudo-noise or spreading code used in CDMA to distinguish one transmission from another.
Interoperability
The ability of devices or systems, often from different vendors, to work and communicate together.
RFC
Request for Comments; a document used to describe, propose, or standardize Internet technologies and protocols.
ANSI
American National Standards Institute; develops and coordinates standards used across industries in the United States.
Millimeter wave
Very high-frequency radio waves with short wavelengths used for in-home networking applications.
Spectrum analyzer
An instrument that displays signal amplitude and frequency, used for antenna alignment and detecting interference.
Horn antenna
A two-dimensional directional antenna resembling a horn, commonly used in telephone networks to transmit microwave signals between distant towers.
Phased array
A smart antenna system using a matrix of radiating elements whose signal phase is varied to focus RF energy in a desired direction.
Antenna azimuth pattern
A radiation pattern showing the shape of the RF signal emitted when viewed from above.
Antenna elevation pattern
A radiation pattern showing the shape of the RF signal emitted when viewed from the side.
Monopole antenna NJIT IT220 CH. 1-6 review questions
A straight conductive element, usually a quarter-wavelength long, with no reflecting element unless paired with a ground plane.
Each of the following is an advantage of using wireless data technology ineducation except: A. Instructors can carry their laptops into the classroom without connectingcables. B. Presentations can be transmitted wirelessly to projector systems C. Students can access the school network from any location. D. Costs are increased by schools that use wireless technologies.
D. Costs are increased by schools that use wireless technologies.
Which of the following is an advantage of wireless technology for a business? A. Employees need a laptop or tablet computer. B. Wireless data access in conference rooms provides employees with immediate access to the data that they need while away from their desk. C. The expense of a wireless network exceeds that of a wired network. D. Wireless networks are always faster than wired networks
B. Wireless data access in conference rooms provides employees with immediate access to the data that they need while away from their desk.
Each of the following is true about the global positioning system (GPS) except: A. It was originally developed by the U.S. military in the late 1970s as a navigation system. B. It is used to provide precise location information. C. A license must be obtained before using it. NJIT IT220 CH. 1-6 review questions D. Devices communicate with earth-orbiting satellites in order to determine their location
C. A license must be obtained before using it
In a warehouse management system radio frequency identification (RFID) tags________. A. emit a wireless data signal that contains an identification number B. are only used when inventory leaves the warehouse C. replace printed labels D. are only found on storage racks and not on pallets
A. emit a wireless data signal that contains an identification number
A _____ is a specific geographic location that is served by a wireless data system. A. JWire B. wireless tag C. Wi-Fi Community (WFC) D. hotspot
D. hotspot
Which of the following is not an advantage of a municipal network? A. Areas with municipal networks can become more attractive to businesses. B. Local municipal employees can use the network to access information. C. ISPs no longer have to provide Internet access. D. Municipal networks provide high speed Internet access for free or at a reduced cost.
C. ISPs no longer have to provide Internet access.
NJIT IT220 CH. 1-6 review questions The _____ refers to the connection that begins at a fast Internet service provider, goes through the local neighborhood, and ends at the home or office. A. last mile connection B. first mile connection C. backhaul connection D. splice
A. last mile connection
_____ are special high-speed circuits leased from a local carrier that can be used to connect remote sites of a business. A. Trunk-based leased lines B. WISPs C. Fronthaul connections D. Fiber merge networks (FMN)
A. Trunk-based leased lines
Each of the following is a limitation of wired networks that wireless networks overcome except: A. A user who shifts the computer on his or her desk may break one or more of the wires in a patch cable. B. A cable splice that is done incorrectly can cause problems that result in intermittent errors that are very difficult to identify. C. Moisture can erode metallic conductors on a network connection. D. Wired networks require that all equipment be IEEE certified
D. Wired networks require that all equipment be IEEE certified
Which of the following is not a disadvantage of a wireless data network? NJIT IT220 CH. 1-6 review questions A. Mobility B. Security C. Interference D. Coverage range
A. Mobility
In a wireless personal area network (WPAN), the maximum distance betweendevices is generally ________. A. 33 feet B. 175 feet C. 3 city blocks D. There is no maximum distance for a WPAN
A. 33 feet
Which of the following is true regarding Bluetooth? A. It is a WWAN technology. B. It was originally designed to replace wires with radio-based technology. C. It cannot support ad hoc connections. D. It consumes a large amount of power
B. It was originally designed to replace wires with radio-based technology.
Typical transmissions speeds for WLANs do not exceed _____ Mbps. A. 11 B. 54 C. 108 D. 600
D. 600
An example of a WMAN technology is ________. A. WLAN B. LTE NJIT IT220 CH. 1-6 review questions C. 2G D. RFID
B. LTE
_____ is a cellular wireless data network technology through which a user can access the Internet. A. 4G B. OFDM C. FFRD D. KRG
A. 4G
Which of the following wireless networks has a maximum speed of 350 Mbps and a coverage area of 350 feet? A. WLAN B. WPAN C. WMAN D. WWAN
A. WLAN
The _____ is responsible for the global management of the radio frequency spectrum. A. International Standards Organization (ISO) B. Federal Communications Commission (FCC) C. International Telecommunication Union Radio Communication Sector (ITU-R) D. Wireless Ethernet Compatibility Alliance (WECA)
C. International Telecommunication Union Radio Communication Sector (ITU-R)
_____ is the primary regulatory agency for wireless communications in the United States and its territorial possessions. A. The Federal Communications Commission (FCC) NJIT IT220 CH. 1-6 review questions B. Wi-Fi C. The Institute of Electrical and Electronics Engineers (IEEE) D. RCID
A. The Federal Communications Commission (FCC)
The _____ is an international body that sets industrial and commercial standards and is composed of representatives from national standards organizations. A. International Organization for Standardization (ISO) B. Federal Communications Commission (FCC) C. Wireless Ethernet Compatibility Alliance (WECA) D. Occupational Standards Institute (OSI)
A. International Organization for Standardization (ISO)
The Wi-Fi Alliance________. A. Certifies that wireless products adhere to the IEEE standards to ensure product interoperability. B. Has been replaced by the ISO C. Is a subgroup of the IEEE D. Only works with large enterprise businesses.
A. Certifies that wireless products adhere to the IEEE standards to ensure product interoperability.
Each of the following is an advantage of standards except A. interoperability B. protection C. more competition D. increased costs
D. increased costs
Standards that set by an official body are called NJIT IT220 CH. 1-6 review questions A. de jure B. de facto C. de rigueur D. de consortia
A. de jure
The current IEEE WLAN standard is A. IEEE 802.11h B. IEEE 802.11-2009 C. OSI/IEEE 802.1x D. IEEE PHY 2008-802.11
B. IEEE 802.11-2009
EEE 802.11 specified that either radio frequency waves or _____ could be used in a WLAN. A. circuit packet transfer (CPT) B. low-frequency emission signals (LFES) C. ultraviolet light D. infrared light
D. infrared light
A(n) _____ transmission requires that the emitter and detector be directly aimed at one another. A. reflected B. diffused C. directed D. indirected
C. directed
Each of the following is a data rate of IEEE 802.11b except A. 54 Mbps B. 1 Mbps C. 5.5 Mbps D. 11 Mbps NJIT IT220 CH. 1-6 review questions
A. 54 Mbps
A mobile wireless device is official known as a(n) A. Mobile Transfer Detector (MTD) B. port C. module D. station
D. station
What happens when a mobile wireless devices moves away from the transmitterin a WLAN? A. nothing; the maximum data rates remain the same no matter how far away thedevice is located B. the connection is dropped after the device moves away more than 10 feet (30meters) C. all authentications must be renegotiated every 3 feet (9 meters) D. the device decreases its data rates to the next lower acceptable data level
D. the device decreases its data rates to the next lower acceptable data level
_____ is the theoretical maximum rated speed of a network. A. data rate B. throughput C. bit/byte rate D. Packet Calculation Level (PCL)
A. data rate
What is the maximum data speed of an IEEE 802.11a WLAN? A. 48 Mbps B. 64 Mbps NJIT IT220 CH. 1-6 review questions C. 68 Mbps D. 54 Mbps
D. 54 Mbps
An IEEE 802.11g network can transmit at the same maximum speed as A. IEEE 802.11b B. IEEE 802.11a C. IEEE 802.11r D. IEEE 802.11x
B. IEEE 802.11a
Each of the following is an improvement of IEEE 802.11n over previous WLAN standards except A. speed B. security C. coverage area D. form factor
D. form factor
13. _____ is a 32-bit bus in the PC Card form factor A. Type IV B. PCCMIA C. EDO D. CardBus
D. CardBus
_____ is a combination of an SD card and an input/output (I/O) device such as awireless NIC. A. Secure Digital Input Output (SDIO) B. CF-PCA C. NIC-CIA D. ExpressCard NJIT IT220 CH. 1-6 review questions
A. Secure Digital Input Output (SDIO)
Which of the following would not be found on a laptop computer? A. Mini-PCMCIA B. Mini-PCI C. Mini-PCI-e D. Type II slot
A. Mini-PCMCIA
An access point consists of each of the following except A. an antenna and a radio transmitter/receiver to send and receive wireless signals B. special bridging software to interface wireless devices to other devices C. a wired network interface that allows it to connect by cable to a standard wired network D. an infrared transmitter/emitter
D. an infrared transmitter/emitter
A(n) _____ does not contain the management and configuration functions A. lightweight access point B. fat access point C. autonomous access point D. switch access point
A. lightweight access point
A(n) _____ does not have to be individually connected by a cable to the existing wired network but instead each device communicates wirelessly with the next closest one. A. backhaul access point NJIT IT220 CH. 1-6 review questions B. thin access point C. fat access point D. mesh access point
D. mesh access point
A wireless workgroup bridge is used to connect A. a wired network segment with a wireless network segment B. a wireless network segment with another wireless network segment C. a gateway and a bridge D. a router and a switch E. mirror slack
A. a wired network segment with a wireless network segment
(n) _____ provides encryption and authentication services for a wireless network and resides between the wireless network and the wired network to serve as the entry point to the wired network. A. remote authentication server B. access point C. mesh hub router D. Enterprise Encryption Gateway (EEG)
A. remote authentication server
Cycles are illustrated by an up-and-down wave called a(n) A. oscillating signal B. cyclical repeater C. AC-to-DC converter D. amplitude
A. oscillating signal
NJIT IT220 CH. 1-6 review questions The distance between peaks of an electromagnetic wave is called the A. hertz B. frequency C. crest D. wavelength
D. wavelength
A million cycles per second is a(n) A. GHz B. MHz C. KHz D. wHz
B. MHz
A weakening electromagnetic signal does not impact which two characteristics? A. Wavelength and frequency B. Phase and amplitude C. Frequency and phase D. Amplitude and volts
A. Wavelength and frequency
Two signals that have the same peaks and valleys are called A. reflected B. 180 degrees out of phase C. out of phase D. in phase
D. in phase
Each of the following is a category of the electromagnetic spectrum except NJIT IT220 CH. 1-6 review questions A. SIM B. X-ray C. microwave D. radio
A. SIM
The number of unlicensed bands that are used for WLANs is A. 2 B. 3 C. 4 D. 5
A. 2
Each of the following is a name for the electromagnetic signal that has been modified to carry information except A. carrier signal B. carrier wave C. carrier D. carrier keying
D. carrier keying
The modification of the height of a digital signal is called A. amplitude modulation (AM) B. frequency modulation (FM) C. phase modulation (PM) D. amplitude shift keying
D. amplitude shift keying
A _____ is a basic unit of power of 1 amp of current that flows at 1 volt. A. V NJIT IT220 CH. 1-6 review questions B. W C. R D. P
B. W
The power that most WLANs transmit is less than A. 2.45 GHz B. 200 mW C. -120 dBm D. 65 V
B. 200 mW
The reference point that relates the logarithmic relative decibel (dB) scale to the linear milliwatt scale is known as the A. decibel milliwatt (dBm) B. decibel (dB) C. milliwatt carrier (mWc) D. R scale
A. decibel milliwatt (dBm)
Which of the following is a typical recommended signal strength for a WLAN? A. 99 dB B. 0.01 mW C. 32 W D. -70 dBm
D. -70 dBm
A loss of 3 decibels means that _____ percent of the power in mW has been lost. A. 25 B. 50 NJIT IT220 CH. 1-6 review questions C. 75 D. 9
B. 50
Each of the following is a reason why RSSI should not be used as a true indicator of signal strength except A. RSSI is not a linear scale B. All possible mW or dBm values may not be represented by the RSSI values C. Each vendor may implement RSSI differently D. RSSI was not intended to be used in this way
A. RSSI is not a linear scale
The materials concrete, wood, and asphalt that "soak up" an RF signal can all cause A. reflection B. refraction C. scattering D. absorption
D. absorption
What is the difference between refraction and diffraction? A. With refraction, the medium through which the signal passes causes the signal to bend, while diffraction is caused by an object in the path of the transmission. B. There is no difference between them. C. Refraction causes signals to be reflected while diffraction causes signals to be absorbed by materials D. Diffraction is caused by rocks and sand while refraction is caused by foliage.
A. With refraction, the medium through which the signal passes causes the signal to bend, while diffraction is caused by an object in the path of the transmission.
NJIT IT220 CH. 1-6 review questions Free space path loss (FSPL) is caused by A. scattering B. reflection C. deflection D. the loss of signal strength as the signal travels
D. the loss of signal strength as the signal travels
A(n) _____ is one billionth of a second. A. picosecond B. millisecond C. microsecond D. nanosecond
D. nanosecond
_____ occurs when a multipath signal arrives 180 degrees out of phase. A. Downfade B. Corruption C. Mirroring D. Nulling
D. Nulling
An intentional radiator (IR) is A. power directed from an antenna B. power directed to an antenna C. one-eighth of a wavelength D. another name for a mini-DPI antenna
B. power directed to an antenna
_____ is the power radiated out by the wireless system and includes any antennagain. A. Antenna Power Source (APS) B. Radiation Power (RP) NJIT IT220 CH. 1-6 review questions C. Equivalent Isotropically Radiated Power (EIRP) D. Dipole Equivalent Isotropic Radiator (DEIR)
C. Equivalent Isotropically Radiated Power (EIRP)
The passive gain increase of power that is funneled from an antenna compared to that of an isotropic radiator is called A. dBi B. dBp C. KHz D. IRP
A. dBi
_____ compares the antenna gain against that of a dipole antenna. A. IERP-D B. dBB C. ERP D. dBd
D. dBd
The orientation of radio waves as they leave an antenna is called A. polarization B. phase C. orientation D. radiation form
A. polarization
APs with multiple antennas employ _____ to improve reception. A. transmit diversity B. polar waves NJIT IT220 CH. 1-6 review questions C. switch master configuration (SMC) D. antenna diversity
D. antenna diversity
Generally, a semidirectional antenna will only transmit its signal no more than_____ degrees. A. 22.5 B. 45 C. 90 D. 180
B. 45
An antenna that divides the entire 360 degrees of coverage area into eight sectors of 45 degrees each is called a(n) A. dipole antenna B. sectorized antenna C. T-antenna D. Phased Dipole Array Configuration (DPAC)
B. sectorized antenna
The outer circle of an antenna radiation chart represents A. a gain that is less than 100 percent B. a gain that is 100 percent C. the location of the antenna D. the power to the antenna
B. a gain that is 100 percent
A(n) _____ chart shows the vertical coverage area of an antenna. A. Azimuth B. elevation NJIT IT220 CH. 1-6 review questions C. Azure D. meter
B. elevation
Beamwidth is considered a measure of the antenna's _____ range. A. half-power B. quarter-power C. full-power D. sector-power
A. half-power
The general rule of thumb is that _____ percent of the first Fresnel zone must be clear of obstacles. A. 60 B. 75 C. 90 D. 100
A. 60
A SISO system has how many radio chains? A. 1 B. 2 C. 3 D. 4
A. 1
_____ sends redundant streams in parallel. A. Co-Op Beamwaving B. Muxplexing C. SISO diversity D. Spatial diversity
D. Spatial diversity
NJIT IT220 CH. 1-6 review questions A wireless device designated as 2x3:1 has how many Rx antennas? A. 1 B. 2 C. 3 D. 6 (3x2)
C. 3
The maximal ratio combining (MRC) algorithm is used when A. a non-MIMO device sends to a MIMO device B. a MIMO device sends to a non-MIMO device C. a SISO device sends to a SISO device D. a MIMO device sends to a MIMO device
D. a MIMO device sends to a MIMO device
Each of the following is a good location for installing an AP except A. on a ceiling B. high on a wall C. in a plenum without a special enclosure D. on a pole
C. in a plenum without a special enclosure
Another name for system operating margin (SOM) is A. additive margin NJIT IT220 CH. 1-6 review questions B. buffer space C. reserve margin D. fade margin
D. fade margin
When the VSWR is indicated in dB it is called the A. downfade B. dBVSWR C. return loss D. power ratio
C. return loss
Which of the following is an advantage of narrowband transmissions? A. The number of chips used B. Interference C. The amount of power used D. The amount of spectrum used
D. The amount of spectrum used
Each of the following is an advantage of spread-spectrum transmissions except A. Resistance to narrowband interference B. Higher power requirements C. More information transmitted D. Resistance to multipath distortion
B. Higher power requirements
Each of the following is a type of spread-spectrum technology except A. FHSS B. DSSS NJIT IT220 CH. 1-6 review questions C. UNII D. OFDM
C. UNII
_____ is the difference between the upper and lower frequencies. A. Bandwidth B. Spread spectrum C. IRP D. Guard interval
A. Bandwidth
In FHSS the amount of time used to change from one frequency to the next is called the A. dwell time B. phase C. hop time D. modulation event (ME)
C. hop time
Which of the following technologies use a chipping code? A. FHSS B. DSSS C. OFDM D. ISM
B. DSSS
When using _____ each device is assigned a unique chipping code in order that all the transmissions can use the same frequency yet remain separate. A. Chip Allocation Standard (CAS) B. shared bandwidth NJIT IT220 CH. 1-6 review questions C. PMDS D. colocation
D. colocation
With OFDM, the _____ is intended to reduce intersymbol interference (ISI). A. presymbol response B. vertical symbol delay (VSD) C. dwell time D. guard interval
D. guard interval
The _____ sublayer reformats the data received from the higher layer into a frame that can be transmitted. A. Physical Medium Dependent (PMD) B. Physical Layer Convergence Procedure (PLCP) C. Media Access Control (MAC) D. Logical Link Control (LLC)
B. Physical Layer Convergence Procedure (PLCP)
DSSS is used by A. 802.11b B. 802.11a C. 802.11n D. 802.11h
A. 802.11b
The PLCP frame preamble and header in 802.11b are always transmitted at _____Mbps. A. 1 B. 2 C. 5.5 D. 11 NJIT IT220 CH. 1-6 review questions
A. 1
Each of the following channels is a nonoverlapping frequency in 802.11b except A. 1 B. 6 C. 8 D. 11
C. 8
Which of the following is not a characteristic of IEEE 802.11a? A. It uses ISM instead of UNII B. The bandwith is 300 MHz C. The range of coverage is less than 802.11b D. The fastest speed is 54 Mbps with an optional proprietary speed of 108 Mbps
A. It uses ISM instead of UNII
_____ transmits a secondary copy along with the primary information to account for errors. A. Forward Error Correction (FEC) B. Multiplexing C. Bandwidth diversity D. DSSS framing
A. Forward Error Correction (FEC)
How many nonoverlapping channels are available in IEEE 802.11a? A. 3 B. 12 C. 23 D. 56 NJIT IT220 CH. 1-6 review questions
C. 23
Two safeguards to protect 802.11n channel bonding from interfering with other WLANs are Dynamic Frequency Selection (DFS) and _____. A. Phased Coexistence Operation (PCO) B. MIMO Substitution C. Channel Allocation D. MIMO Branching (MIBRA)
A. Phased Coexistence Operation (PCO)
The ability to adjust the "quiet" period between OFDM symbols to allow for the arrival of late symbols in 802.11n is called A. ISI delay B. space allocation C. modulation adjustment D. variable guard interval (VGI)
D. variable guard interval (VGI)
All of the possible combinations of different factors for 802.11n transmissions are contained in the A. UNII Procedures Manual B. Wi-Fi Table C. IEEE 802.11n Resource Guide D. Modulation and Coding Scheme (MCS)
D. Modulation and Coding Scheme (MCS)
The abbreviation s stands for A. microsecond B. millisecond C. nanosecond D. kilosecond NJIT IT220 CH. 1-6 review questions
A. microsecond
A numeric value that is assigned to a frequency range is called the A. downfade B. bandwidth C. modulation D. channel
D. channel
How many different service sets are available in IEEE 802.11? A. three B. four C. five D. six
A. three
A(n) _______ consists of one or more stations that are served by a single access point. A. Basic Service Set (BSS) B. Hybrid Service Set (HSS) C. Extended Service Set (ESS) D. Independent Extended Service Set (IESS)
A. Basic Service Set (BSS)
Each of the following is a name for a service that that does not use an AP except A. Ad Hoc B. Peer-to-peer C. Basic Service Set D. Independent Basic Service Set
C. Basic Service Set
NJIT IT220 CH. 1-6 review questions A(n) _____ describes a specific unit of data that has been passed down from a higher OSI layer to a lower layer but has not yet been encapsulated by that lower layer. A. Extended MAC Protocol Data Unit (X-MPDU) B. Aggregate Data Unit (ADU) C. Protocol Data Unit (PDU) D. Service Data Unit (SDU)
D. Service Data Unit (SDU)
What is a restriction that applies to A-MPDUs? A. They cannot use OFDM. B. All of the A-MPDUs within the single A-MPDU must be addressed to the same receiver. C. They must all share the same hop time. D. There are no restrictions.
B. All of the A-MPDUs within the single A-MPDU must be addressed to the same receiver.
Each of the following is an option for addressing differences in frame size except A. Lowest common denominator B. Jumbo Frames C. fragmentation D. maximum transmission unit splicing (MTUS)
D. maximum transmission unit splicing (MTUS)
In _____ mode an IEEE 802.11a/b/g device will not be able to access the AP. A. HT Nonmember Protection B. Greenfield C. HT Mixed D. Non-HT NJIT IT220 CH. 1-6 review questions
B. Greenfield
_____ frames are used to set up the initial communications between a device and the access point. A. Control B. Management C. Initialization D. Data
B. Management
_____ is when the AP transmits its beacon frame and a station is looking for those frames. A. Passive scanning B. Beacon reconnaissance (BR) C. SSID allocation D. WLAN resource allocation
A. Passive scanning
What happens if a probe request frame contains a null value? A. All APs will respond. B. No APs will respond. C. Only APs with a null SSID will respond. D. An error message is generated and sent to the AP
A. All APs will respond.
_____ is the process in which an AP accepts a station into the WLAN. A. Authentication B. Authorization C. Acceptance D. Reception
A. Authentication
NJIT IT220 CH. 1-6 review questions Which of the following uses a challenge text? A. Open system authentication B. Shared key authentication C. Challenge authorization D. Encryption management
B. Shared key authentication
Which of the following is the default access method for IEEE 802.11 WLANs? A. Carrier Sense Multiple Access with Collision Detection (CSMA/CD) B. Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) C. Carrier Sense Multiple Access with Collision Mitigation (CSMA/CM) D. Carrier Sense Multiple Access with Collision Routing (CSMA/CR)
B. Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)
Which of the following is false regarding block acknowledgment? A. It only applies to IEEE 802.11n. B. It supports multiple MPDUs in an A-MPDU. C. The receiving node sends a block ACK only acknowledging the correct MPDUs. D. The sender then will retransmit all MPDUs.
D. The sender then will retransmit all MPDUs.
_____ reserves the medium for a period of time and handles the hidden node problem. A. Carrier Sense Multiple Access with Collision Detection (CSMA/CD) NJIT IT220 CH. 1-6 review questions B. NVA C. Request to Send/Clear to Send (RTS/CTS) D. DFC
C. Request to Send/Clear to Send (RTS/CTS)
Which is used when 802.11g devices are mixed with 802.11b devices together? A. CTS-to-self B. HT Dual-CTS Protection C. HT L-SIG Protection D. RTS/GHS
A. CTS-to-self
Which of the following interframe spaces is used for immediate response actions such as ACK and has the highest level of priority? A. Distributed Coordination Function IFS (DIFS) B. Arbitration IFS (AIFS) C. Short IFS (SIFS) D. Point Coordination Function IFS (PIFS)
C. Short IFS (SIFS)
_____ is an optional polling mechanism. A. Point Coordination Function (PCF) B. Polling Contact C. RTS/CTS D. Synchronization Access Method
A. Point Coordination Function (PCF)
The hybrid coordination function (HCF) allows for different types of wireless traffic to be given different levels of _____. A. speed NJIT IT220 CH. 1-6 review questions B. priority C. frame size D. backoff procedures
B. priority
Each of the following is an Enhanced Distributed Channel Access (EDCA) access category (AC) except A. Background (AC_BK) B. Foreground (AC_FG) C. Best Effort (AC_BE) D. Video (AC_VI)
B. Foreground (AC_FG)