Wireless Communications Fundamentals

134 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: A straight conductive element, usually a quarter-wavelength long, with no reflecting element unless paired with a ground plane.